2-d monte carlo integration help

First, I'd like to thank everyone that willingly gives their time to help, thank you!!

*NOTE: This is for school, and I am NOT wanting someone to just do this for me or give answers. I just need some tutoring and help because I am completely lost and have made 0 to little progress (I'll post what have done at the end.)

Right now I'm trying to write a program that makes a rectangle, and inside the rectangle is a circle. Virtual darts are thrown via the rand function, and the area of the circle is calculated based on hit / misses. Here are some details:

-I need to compute the area of a shape (circle) by throwing virtual darts
-Produce a tester that tells if my code is working

At the end of the program the following should be printed out:

1. Length and width of enclosing rectangle
2. Area of enclosing rectangle
3. Number of darts thrown
4. How many darts hit the shape
5. Percentage of darts that hit the shape
6. Area of the shape computed by out dart throwing
7. Actual area of shape as known from an equation
8. The absolute value difference between these quantities (i.e., the error)

In the tester we must provide the function: void GetBorders (double *xmin, double *xmax, double *ymin, double *ymax);

I'm particularly confused here, am I suppose to make a GetBorders function, then call the function in the tester function?

Here's some pseudo code that was provided:

TESTER:
(1) Write function for shape we know answer to
--> circle has area PI*r*r
--> Easy to write function for circle wt center on axis!
--> Answer 1 if distance of (x,y) from axis <= r
--> distance: sqrt(x*x + y*y) (pythagorean theorem):
** draw grid wt triangle, to show how hypotenuse is the distance
--> RETURN 1 if sqrt(x*x + y*y) <= r, ELSE 0
==> Call this function:
int DartHits(double x, double y)
(2) Have known answer of area as formula
-> circle is PI*R*R
-> make PI and R cpp macros so we can vary easily
(3) Compare known area to area computed by throwing darts!


And for the other functon:

ThrowDarts:

(1) Get how many darts to throw
--> N, read in from keyboard, store as unsigned long int
(2) Get coordinates of surrounding rectangle
--> xmin: x coordinate of left side of rectangle, which is known to be
less than smallest X value of function
--> xmax: x coordinate of right side of rectangle, >= largest X val of func
--> ymin,ymax: same for Y lower/upper of rectangle
==> types must be double, since points are continuous!
==> double xmin, xmax, ymin, ymax
==> These values must be supplied by tester, since they are tied to the
function being evaluated!
==> we will have tester supply all four values using function:
--> void GetBorders(double *xmin, double *xmax,
double *ymin, double *ymax);
(3) Compute area of rectangle:
--> Area of rect = length * width = (xmax - xmin) * (ymax - ymin)
(4) Loop over N darts thrown, and count hits
a. Generate random # between [xmin,xmax]; call this xdart (xcoord of dart)
-> call xdart = RandNumInRange(xmin, xmax);
b. Generate random # between [ymin,ymax]; call this ydart (ycoord of dart)
-> call ydart = RandNumInRange(ymin, ymax);
c. hit = DartHits(xdart, ydart);
e. if hit != 0, add one to # of hits
(5) Compute area as: rectArea*(percent hits) = rectArea*(nhits/N)
--> Make sure nhits/N computed as a double to avoid integer truncation!
** How do we get a number between xmin, xmax (more generally between w & z)
-> man -a rand brings up manpage
-> set seed using srand
-> rand(void) returns a number between [0, RAND_MAX]
-> Can change integer between [0,RAND_MAX] to real between [0,1]:
- interpret rand() and RAND_MAX as doubles, and simply divide them:
* rn = ((double)rand())/((double)RAND_MAX); /* real between [0,1] */
* make span any distance by multiplying by distance
- Distance is z-w (z known to be >= to w)
* Make start at particular value by adding starting value in
(will change ending value by same amount, so be prepared for that)
==> Can write func:
double RandNumInRange(double W, double Z)


And for what I have so far, I started the Throw Darts bit first, because I am understanding that part slightly more.

Code:

---

#include <stdio.h>
#define PI 3.14159
#define RADIUS 5


int main (void)


{


int n; /* How many darts to throw. */


printf(" Please enter how man virtual darts you would like to throw: \n\n ");


scanf("%d", &n);


/* Need to call GetBorders function here*/ // Why are they pointers?


int rectArea = (xmax - xmin) * (ymax - ymin);


while ( 1 <= n ) //Started the loop, but I'm not sure what it actually is looping because the instructions seemed arbitrary for making this loop


{






return 0;


}

---

I'm so lost at the moment I'm not even sure what else I should ask, but any advice / tips / tutoring is GREATLY appreciated. Again this is homework for me, please do not post answers. Thanks everyone!!!

What an interesting assignment! :cool:

I wouldn't start with code with this. A whiteboard or paper and pen would be better by far. Until you can visualize at least a portion of what your program needs to do, don't code a darn thing.

There will be a rectangle shown on the display. Your program will randomly hit a location, somewhere inside that rectangle. Some darts will hit the invisible circle inside the rectangle, others will miss the circle. Your program will receive the x and y points of the dart strikes.

Based on numerous darts hits and misses, your program will begin to learn about the position and radius (size) of the invisible circle. Of course, your program will have to know exactly where the circle is located, and what it's size is, because otherwise, it wouldn't be able to tell if the dart throw was a hit on the circle, or a miss. But for the sake of the simulation, your program should not use that information. Instead it should solve the location and size of the circle, with it's own logic, using the dart's data.

There's a little bit of geometry involved, but nothing to cringe about.

Work out how this simulation might go, by paper and pen FIRST. Throw several virtual darts, and by recording where they landed, see if they landed inside an invisible circle inside the rectangle of the paper.

If they DID hit the circle, then that spot MUST be less than or equal distance to the hypotenuse back to the center of the circle. (the radius of the circle, from the center of the circle, to the point the dart landed on).

After awhile, you'll see the logic of parts of the simulation you need. That will form the basic part of the logic for your program.

Give that a try with paper and pen, and work it through by hand first. Note whether the circle's center can be anywhere inside the rectangle, or is it always centered in the rectangle?

P.S.
Welcome to the forum, jsuite! :cool:

Hey, thank you so much for your time and help! I'm going to take your advice. One I finish working it through with pen and paper and by hand I'll update the code, and ask questions from there if need be. Thanks also for the warm welcome, please try to stay updated with this thread! :D Again, thank you!!

Start your update, with a list of the required functions, (just empty of code for now), from your assignment. It has very specific requirements - what variables go where, etc.

The number of dart throws should be stored in the ThrowDarts function, and be labeled N (not in main() as n). All the required stuff listed above, can then be put into the right functions, accordingly.

Okay, sweet! I'm slowly working on it (studying for other things aswell, very loaded this weekend) so expect an update sometime this evening. But there is one question I have, what do I do with main? That's something that was really confusing me, it never mentions main... I know for example, that if a variable need not be static, then I can put it in there... So one idea I have id that my main should have world variables, and also the final print out statements?

Quote:

---

Originally Posted by jsuite

Okay, sweet! I'm slowly working on it (studying for other things aswell, very loaded this weekend) so expect an update sometime this evening. But there is one question I have, what do I do with main? That's something that was really confusing me, it never mentions main... I know for example, that if a variable need not be static, then I can put it in there... So one idea I have id that my main should have world variables, and also the final print out statements?

---

Programs in C usually have 3 functional parts - Input, Calculation/s, and Output. In a small program, all three can fit nicely inside main(), but on larger programs, you may need one or more functions, for each of these parts of the program.

Try thinking of main() as the starting point for your program, and the subsequent point of return. It could be just two lines of code, or several blocks of code.

Since several other functions have specific requirements, I'd get them set up first - even if the requirements are not coded, but just listed in notes:

Code:

---


//?? ThrowDarts(unknown) {
 /*    gets unsigned long N for number of darts to be thrown from the user */ //kind of thing.

  //return??
//}

---

Save the contents of main() and other non-required (by the assignment) functions, until later. You can be much more flexible with them. Use them for "glue", to make the logic flow OK.

In general, list the requirements, inside the required functions (if known), but put off all the details that are not important, until you get the core logic flowing.

Once the core logic is working, then add in the details. Saves a lot of time.

Global variables (which have program-wide scope), are listed above main(). They can be useful, but are a negative on the whole purpose of functions (which is to encapsulate a portion of the program). Use them VERY sparingly, if at all.

Remember not to rely on rand() or random() family of functions in C, as they are linear congruential pseudorandom number generators (Wikipedia), and are likely to introduce artefacts/errors when used in Monte Carlo stuff. I warmly recommend using Xorshift instead. In particular:

Code:

---

#include <stdint.h>

static uint32_t prng_state[4] = {
        123456789U,
        362436069U,
        521288629U,
        88675123U
};

static inline uint32_t prng_u32(void)
{
        uint32_t        temp;

        temp = prng_state[0] ^ (prng_state[0] << 11U);
        prng_state[0] = prng_state[1];
        prng_state[1] = prng_state[2];
        prng_state[2] = prng_state[3];
        return prng_state[3] ^= (temp >> 8U) ^ temp ^ (prng_state[3] >> 19U);
}

/* 0.0 <= prng_one() < 1.0 */
static inline double prng_one(void)
{
        return (double)prng_u32() / 18446744073709551616.0
            + (double)prng_u32() / 4294967296.0;
}

---

To randomize the generator, set the four 32-bit unsigned integers in prng_state[] to anything (except all four to zero). In prng_one() the divisors are powers of two, so on most architectures they are either optimized away, or implemented as very fast multiplications or bit shifts. It is seriously fast, and produces excellent pseudorandom numbers.

Although Adak gave you excellent advice, I think you can make it even easier for yourself, if you think in terms of centerpoints.

Compute the centerpoint for the rectangle and the circle, the width and height of the rectangle, and the squared radius of the circle:

Code:

---

    /* Assuming xmin, xmax, ymin, ymax are the rectangle,
    * circle has radius radius, and the circle is centered on the rectangle. */
    const double  rect_width = xmax - xmin;
    const double  rect_height = ymax - ymin;
    const double  rect_x = xmin;  /* Minimum x for the rectangle */
    const double  rect_y = ymin;  /* Minimum y for the rectangle */
    const double  circle_x = 0.5 * (xmin + xmax); /* Center at center of rectangle! */
    const double  circle_y = 0.5 * (ymin + ymax); /* Center at center of rectangle! */
    const double  circle_squared = radius * radius;

---

To generate a random point within the rectangle, you generate a point in the unit square (0,0)-(1,1), scaled and moved to cover the desired rectangle:

Code:

---

    x = rect_x + rect_width * prng_one();
    y = rect_y + rect_height * prng_one();

---

The distance squared from point (x,y) to the center of the circle is, as Adak explained, described by the Pythagorean theorem, where the length of the two sides are x-circle_x and y-circle_y. In other words,

Code:

---

    if ( (x-circle_x)*(x-circle_x) + (y - circle_y)*(y - circle_y) <= circle_squared ) {
        /* Point (x,y) is within the circle.
        * (If == circle_squared, then the point is on the circumference of the circle.) */
    }

---

For fun, I wrote a test program which takes all the parameters from the command line, checks them, and does the 2D Monte Carlo integration using the above Xorshift implementation as random number source. It works fine (as in yields the expected results at expected precision), and is just over a hundred lines of code (not counting empty lines).

Very interesting note about circles inside squares about half way down the page, with a pic (applet):
Approximations of

Okay, so I worked on it some, tried to do what I could. I must say I'm embarrassed at how little I can do thus far. I really got screwed with this course because my curriculum calls for us to start on java (which i did) then it switches us to c (what I'm in now). Long story short I chose a professor who I knew was reputable, but the changed my professor dude to an influx of computer science students this year, so they had to add and shuffle around professors. Well I get stuck with a young woman who is not very good at teaching. The problem is, the head of the department is very strict and tells her what to teach, but she never gets to everything, so when I get a project (The project is made by the head of the department) it's vey challenging, because now I have to go back and teach myself everything that she failed to even bring up. Anyways, here's what I have to far, I'm going to keep chiseling away at it.

Code:

---



#include <stdio.h>
#define PI 3.14159
#define RADIUS 10


int main (void)


{


//stuff


}






tester() /* tester function */
{


double  cirArea = PI * RADIUS * RADIUS;
double distance = sqrt(x*x + y*y); /* This is the Pythagorean that i'm suppose to use, where does the x and y come from?*/
/* The circle is suppose to be centered at (0,0) so if I've chosen my radius to be 10, i can calculat x and y? */


//Here I'm suppose to draw grid with triangle, to show how hypotenuse is distance.. How do I draw it?


if (distance <= RADIUS)
  return 1;


else
  return 0;


// call the function int DartHits(double x, double y); here
// This functions is how we know the estimated area of circle


//Now we compare actual area vs. estmated area. I think the mean print out statement?
//like this:


printf("The actual area is %f, and the estimated area is %d /n", cirAreal, DartHits);


}




ThrowDarts() /* ThrowDarts function */


{


int n;
int i;


printf("How many darts would you like to throw?");
scanf("%d", &n); /* Prompts user for how many darts to throw, and saves it n */


/* completely lost on the next step: I'm suppose to call the function void
GetBorders(double *xmin, double *xmax, double *ymin, double *ymax); and it says that
all four of these values are supplied by the tester function. So is Getborders
 seperate function, or is it inside the tester function? Very confused here. */


int rectArea = (xmax - xmin) * (ymax - ymin);


for (i = 1; i <= n, i++)
    // The following should go under this for loop:


    /* a. Generate random # between [xmin,xmax]; call this xdart (xcoord of dart)
    -> call xdart = RandNumInRange(xmin, xmax);
    b. Generate random # between [ymin,ymax]; call this ydart (ycoord of dart)
    -> call ydart = RandNumInRange(ymin, ymax);
    c. hit = DartHits(xdart, ydart);
    e. if hit != 0, add one to # of hits */


// One thing that confuses me is, in part a and b above
// It says to take a variable like xdart and ydart, then
// make them = to functions? How does that work?
// also those instructions say get a random number between xmin and xmax
// and call that number x dart
// then on the next like it says make xdart = a function???




double  estRectArea = rectArea * (nhits/n); //nhits is number of hits, generated by for loop above




/* and the last part of this function is suppose to be how they want us to calculate rand

/* ** How do we get a number between xmin, xmax (more generally between w & z)
-> man -a rand brings up manpage
-> set seed using srand
-> rand(void) returns a number between [0, RAND_MAX]
-> Can change integer between [0,RAND_MAX] to real between [0,1]:
- interpret rand() and RAND_MAX as doubles, and simply divide them:
* rn = ((double)rand())/((double)RAND_MAX);  real between [0,1]
* make span any distance by multiplying by distance
- Distance is z-w (z known to be >= to w)
* Make start at particular value by adding starting value in
(will change ending value by same amount, so be prepared for that)
==> Can write func:
double RandNumInRange(double W, double Z) */


}


    return 0;


}

---

A lot of questions I have are in the code comment.

Also, the circle is centered at (0,0).

Quote:

---

Originally Posted by jsuite

Also, the circle is centered at (0,0).

---

Good to know.

In ThrowDarts(), the number of darts variable should be N, (uppercase, no idea of why), and the data type should be an unsigned long int, instead of a regular int.

GetBorders() will get from the user, where the top, bottom, left and right borders for the rectangle will be. It should be called only once when the program starts, which matches up with getting the number of darts that will be thrown. I'd put this prototype right inside ThrowDarts, itself, and call it from inside ThrowDarts.

double xmin, ymin,xmax,ymax;
xmin=1;ymin=1;
xmax=79;ymax=30 to 40;

If you write to the 80th column of the display, the cursor will automatically do a line feed, and wreck your display badly. I believe we want the max-min of both x and y, to be odd numbers. Otherwise you won't have a true center for the rectangle.
:(

_gotoxy(xmin,ymin); printf("*"); _gotoxy(xmax,ymax); printf("*");getchar();

The above is what I can see in a console on Windows, depending on the properties and fonts I have set up for that window.

Try it and see what you can see (upper left and lower right corners only), without the screen rolling or the cursor adding a newline.

You have conio.h?

It's best if we zero in on ThrowDarts function first, and include GetBorders function since it's required for ThrowDarts to work.

Best if you make comments OUTSIDE the code. Otherwise my comments back will be inside the code, and that may look to someone like I'm writing your program.

Ok to address your post above: Thank you so much for the response! About the GetBorders functions and the prototype, well he wants us to use void GetBorders (double *xmin, double *xmax, double *ymin, double *ymax). I find this absurd BUT the point is to practice with pointers, it was a challenge for me t figure out how to properly call it. Then it dawned on me, this is similar to a swap (*pointer, *pointer) function.

Also, I don't think I'm actually suppose to draw the shapes? I can check about using conio., but graphics.h did nt work for me. I'm using vim editor in ubuntu 12.01 btw.

Good news though, I have made significant progress. I have a few huge questions Ill ask after I put the code here:

Code:

---

---

Code:

---

#include <stdio.h>
#define PI 3.14159
#define RADIUS 10


void GetBorders(double *xmin, double *xmax, double *ymin, double *ymax)
{


double a, b, c, d;


a = 27;
b = 57;
c = 33;
d = 67;


*xmin = a;
*xmax = b;
*ymin = c;
*ymax = d;
}


Tester()
{
double xmax, xmin, ymax, ymin;


double cirArea = PI * RADIUS * RADIUS;


GetBorders(&xmin, &xmax, &ymin, &ymax);
}


ThrowDarts()
{
double n;
printf("How many darts would you like to throw?");
scanf("&d", &llu);


double xmax, xmin, ymax, ymin;
GetBorders(&xmin, &xmax, &ymin, &ymax);
double rectArea = (xmax -xmin) * (ymax - ymin);


double xdart;
double ydart;
int i = 1;


//loop goes here:
while (i <= n)
    double nhit;


    xdart = rand(xmin,xmax); //generate random number between xmin and xmax
      xdart = RandNumInRange(xmin,xmax);
   
    ydart = rand(ymin,ymax); //generate random number between ymin and ymax
      ydart = RandNumInRange(ymin,ymax);


    nhit = DartHits(xdart, ydart);
      if (nhit != 0)
        nhit++;


double estRectArea = rectArea * (nhit/n);
}


double RandNumInRange (double w, double z)
{






}


int main (void)
{
}



---

Questions:

The RandNumInRange - I don't know where to start. It needs to pick a random number in a range, and use a seed. Tried googling about seeds, but they are all explained relative to time.h. I'm not suppose to use time.h. So what are seeds, and can you explain what I should be doing when making this function?

*Note: things are all out of order, I know. Once I get the RanNumInRange function figured out, ill be fine tuning it, which I'm sure will lead me to more questions. Also the reason why I was super super lost at the very beginning is that I was missing out on some super super fundamental rules of C. (lol) I'll spare you the details though.

The random number generator in C is designed to be able to repeat the sequence at will (using the same compiled program in the same OS using the same libraries). This means that you can reproduce the data anytime you want.
Basically it does this by using a number for each sequence.
you have sequence 1: it starts with 674532, then 5421, then 9811111, ..., ... (numbers made up)
you have sequence 2: it starts with 3145, then 3312967, then 7777, ..., ... (numbers made up)

If you don't specify a sequence for the random number generator it uses sequence 1.
You can basically pretend to specify a random sequence by using the number of seconds since sometime in 1970 (the return value of time(NULL)) by using srand(time(NULL)).

srand() instructs the random number generator to use the numbered sequence; rand() retrieves the next number from the "active" sequence.


Basically you use srand() once for the whole application (whether with a predefined sequence number or a "random" one is irrelevant) and rand() as often as needed.

This program shows a couple ways to get random numbers. The first one gives a double variable, an random number in the range you want. The double always ends with .0, which is to say, it's always a whole number.

The second way it shows to get a random number, is to give a real double, in the range of 0-1. That can obviously be boosted, but it's one of the requirements for your program.

Code:

---

#include <stdio.h>
#include <stdlib.h>


int main(void) {
  double xmin, xmax, ymin, ymax,rnumd;
  int i, rnum,xmaxi;

  srand(1);

  for(i=0,xmax=30;i<300;i++) {
      /* gives even doubles between 1 and xmax */
      //rnumd = (double) (rand() % (int) (xmax +1));  //run me too, but comment

      /* gives random doubles between 0 and 1 */      //this line out when you run it.
      rnumd = ((double)rand()/(double)RAND_MAX);
   
      printf("%5.2f  ",rnumd);
  }
  printf("\n");
  return 0;
}

---

srand(someInteger), "seeds" the random number generator with a string of digits. Each seed number gives a different string of random numbers.

If you give the same seed number (or no seed number), or you don't call srand() before calling rand(), your string of random numbers will always be the same (very good for testing purposes). You should call srand() only ONCE each time the program starts. NEVER repeat the call, thinking you'll get a more random number - you won't.

rand() is not a great random number generator, but it's MORE than what you need for this program.

Quote:

---

Originally Posted by Adak

rand() is not a great random number generator, but it's MORE than what you need for this program.

---

Adak, I agree it is enough for this exact program. However, in the context of the title of this thread, "2-d monte carlo integration help", rand() is not good enough.

Traditionally RAND_MAX has been very small, typically 32767. Regardless of its period (the length of the sequence of numbers it generates), you can have at most (RAND_MAX+1)² unique random 2D dart positions. On a typical desktop machine, that takes just seconds, not minutes.

In Linux, RAND_MAX == 2147483647, but the generator is still weak; the dart positions form a quite regular lattice. I also think it generates much fewer than (RAND_MAX+1)² unique 2D points, but I haven't verified that.

While using srand() and rand() is okay for the purposes of an exercise, it is never okay to use it with Monte Carlo stuff, it is simply not random enough. The implementation may work, but it is does not use true random sampling; it'll use some implementation-dependent regular or semi-regular sampling scheme. And that's not Monte Carlo, is it?

Instead of random sampling, using a linear congruential pseudorandom number generator like rand() and random(), leads to a sampling pattern that approaches a uniform lattice as the number of samples increases. This is most evident if you draw the points into a picture, and watch it fill up.

Furthermore, using (double)rand()/(double)RAND_MAX will only give you RAND_MAX+1 unique values -- just 32768 on many non-Linux systems! The smallest nonzero value (double)rand() / ((double)RAND_MAX + 1.0) returns may be as big as 0.00003, and the largest 0.99997. In other words, less than five significant digits..

The Xorshift alternative I showed in this thread does not suffer from these issues at all, and the prng_one() yields all doubles within [0, 1), about eighteen significant digits per value.

To OP:

While I understand this is just for an exercise, it is very important to realize the impact a poor random number generator has on Monte Carlo and other random-number based computations. It is very common, and very easy to just overlook that, and assume the results are good. Most often the result itself is okay, but the error bars obtained from the sampling statistics may be completely bogus, wonkified by the non-random random number generator used.

In this particular exercise you don't need to use random sampling; a regular sampling will give you the best answer anyway. The reason why should be obvious, right? Because of that, Adak is absolutely correct: rand() will work just fine for this program.

I apologize for harping about this so much; I'll try and be quiet now.

can someone show how to write the code for random, I don't understand clearly

Quote:

---

Originally Posted by shootingstars

can someone show how to write the code for random, I don't understand clearly

---

You said it, Pal! That's one of the next issues that needs to be nailed down. Stay tuned. Run the snippet program in reply #15, and run it with both of the options (one at a time), to see what they do.

@Nominal Animal:
Please, hop off the "random" soap box. It's all true, (and great info), but not needed here (yet).

Wow I appreciate all the info on rand! Unfortunately as the instructions say, I must use rand.

Adak: Your rand function helped a lot, but one minor thing i need to make it work with:

Ill right some generic code here real quick:

randNumInRange(int w, int x) (where w is the max, and x is the min)
{

do stuff / arguments here



My point is (don't know the terminology) but it's a general function, so I can pass it in any other function as randNumInRange(insert max variable here, min variable here) So when I call on it, I can pass any min / max through it. Hope this makes since, you definitely have me on the right track, working on it now. Thanks!!

ps. Ill ask more about getting the function to work if I run into errors. :D

how do you work on the code so far?I think we study same class

I've made a lot of progress, almost finished actually.

you are so great,I think I can not finish this one although I already try my best,I have no experience with C before

Adak, I get errors when I try to compile your code. Here they are:



/usr/include/stdlib.h:140:1: error: unknown type name ‘size_t’
In file included from ran.c:2:0:
/usr/include/stdlib.h:337:4: error: unknown type name ‘size_t’
/usr/include/stdlib.h:367:4: error: unknown type name ‘size_t’
/usr/include/stdlib.h:471:22: error: unknown type name ‘size_t’
/usr/include/stdlib.h:473:22: error: unknown type name ‘size_t’
/usr/include/stdlib.h:473:38: error: unknown type name ‘size_t’
/usr/include/stdlib.h:485:36: error: unknown type name ‘size_t’
In file included from /usr/include/stdlib.h:497:0,
from ran.c:2:
/usr/include/alloca.h:33:22: error: unknown type name ‘size_t’
In file included from ran.c:2:0:
/usr/include/stdlib.h:503:22: error: unknown type name ‘size_t’
/usr/include/stdlib.h:508:45: error: unknown type name ‘size_t’
/usr/include/stdlib.h:508:65: error: unknown type name ‘size_t’
/usr/include/stdlib.h:756:9: error: unknown type name ‘size_t’
/usr/include/stdlib.h:756:25: error: unknown type name ‘size_t’
/usr/include/stdlib.h:761:34: error: unknown type name ‘size_t’
/usr/include/stdlib.h:761:50: error: unknown type name ‘size_t’
/usr/include/stdlib.h:840:6: error: unknown type name ‘size_t’
/usr/include/stdlib.h:843:6: error: unknown type name ‘size_t’
/usr/include/stdlib.h:847:31: error: unknown type name ‘size_t’
/usr/include/stdlib.h:851:31: error: unknown type name ‘size_t’
/usr/include/stdlib.h:860:38: error: unknown type name ‘size_t’
/usr/include/stdlib.h:864:36: error: unknown type name ‘size_t’
/usr/include/stdlib.h:871:1: error: unknown type name ‘size_t’
/usr/include/stdlib.h:872:34: error: unknown type name ‘size_t’
/usr/include/stdlib.h:874:1: error: unknown type name ‘size_t’
/usr/include/stdlib.h:875:40: error: unknown type name ‘size_t’
ran.c: In function ‘main’:
ran.c:18:7: warning: incompatible implicit declaration of built-in function ‘printf’ [enabled by default]
ran.c:20:4: warning: incompatible implicit declaration of built-in function ‘printf’ [enabled by default]


I think there's number truncation going on..

and stdlib not supported?

NEVER MIND #include ,stdio.h> got cut off when ipasted it over.

Ok so the second snippet, the one between 0 and 1... That one is how they want it to be done BUT that one produces decimals. Such as .23, etc.. The first one behaves correctly, but isn't the the wat he wants us to do it. So, I need to make the second snippet produce doubles that are whole numbers (12.0, 40.0, 70,0) etc...

ok so when I try this:

Code:

---


#include <stdio.h>
#include <stdlib.h>
double RandNumInRange (double, double);




int main (void)
{
double xmax, xmin;


xmax = 50;


xmin = 10;


double rand = RandNumInRange (xmin, xmax);


printf("\n\nThe Random Number In Range = %f \n\n\n", rand);
}


double RandNumInRange (double z, double w) //where w is any max value, and z is any min value
{
  double rn;
  int i = 0;
  srand(1);


  while (i<1)
    i++;
    rn = ((double)rand()/(double)RAND_MAX)*(w-z);




  }

---

I get the same number over and over again. Any ideas? D:

The number only changes when I change the seed, also it's not a whole number.

Code:

---

while (i<1)
    i++;
    rn = ((double)rand()/(double)RAND_MAX)*(w-z);


//You are missing '{' and '}' in your while statement

---

There is no return value

Urgent question: This is needed for the loop in ThrowDarts. So Throw darts basically checks if X and Y are inside the rectangle, then at the end of the loop it takes the number in range of x, and number in range of y, and then checks if it's inside the circle. How do I know if those numbers are in the coordinates of the circle? Basically need help / explanation of DartHits function.

Part c of loop instructions:

(4) Loop over N darts thrown, and count hits
a. Generate random # between [xmin,xmax]; call this xdart (xcoord of dart)
-> call xdart = RandNumInRange(xmin, xmax);
b. Generate random # between [ymin,ymax]; call this ydart (ycoord of dart)
-> call ydart = RandNumInRange(ymin, ymax);
c. hit = DartHits(xdart, ydart);
e. if hit != 0, add one to # of hits

Found the answer:

TESTER:
(1) Write function for shape we know answer to
--> circle has area PI*r*r
--> Easy to write function for circle wt center on axis!
--> Answer 1 if distance of (x,y) from axis <= r
--> distance: sqrt(x*x + y*y) (pythagorean theorem):
** draw grid wt triangle, to show how hypotenuse is the distance
--> RETURN 1 if sqrt(x*x + y*y) <= r, ELSE 0
==> Call this function:
int DartHits(double x, double y)


So due to the mixed references to "tester" I'm guessing "tester" is more than one function, instead a couple of functions that come before ThrowDarts()?

Quote:

---

Originally Posted by shootingstars

you are so great,I think I can not finish this one although I already try my best,I have no experience with C before

---

@shootingstars:

Post up your code, and best if you start it in a new thread so it gets the attention it deserves.

Once you get it started, we can help - just tell us what the problem/s is/are.

Do it ASAP, because it will take time.

Quote:

---

Originally Posted by jsuite

Urgent question: This is needed for the loop in ThrowDarts. So Throw darts basically checks if X and Y are inside the rectangle, then at the end of the loop it takes the number in range of x, and number in range of y, and then checks if it's inside the circle. How do I know if those numbers are in the coordinates of the circle? Basically need help / explanation of DartHits function.

Part c of loop instructions:

(4) Loop over N darts thrown, and count hits
a. Generate random # between [xmin,xmax]; call this xdart (xcoord of dart)
-> call xdart = RandNumInRange(xmin, xmax);
b. Generate random # between [ymin,ymax]; call this ydart (ycoord of dart)
-> call ydart = RandNumInRange(ymin, ymax);
c. hit = DartHits(xdart, ydart);
e. if hit != 0, add one to # of hits

Found the answer:

TESTER:
(1) Write function for shape we know answer to
--> circle has area PI*r*r
--> Easy to write function for circle wt center on axis!
--> Answer 1 if distance of (x,y) from axis <= r
--> distance: sqrt(x*x + y*y) (pythagorean theorem):
** draw grid wt triangle, to show how hypotenuse is the distance
--> RETURN 1 if sqrt(x*x + y*y) <= r, ELSE 0
==> Call this function:
int DartHits(double x, double y)


So due to the mixed references to "tester" I'm guessing "tester" is more than one function, instead a couple of functions that come before ThrowDarts()?

---

Actually, I was wondering if "tester" was BOTH a function, AND sometimes referred to the program "testing" in the simulation. It is confusing.

This is just the Pythagorean theorem:
RETURN 1 if sqrt(x*x + y*y) <= r, ELSE 0

Where x = A, y = B, and r = C² in A² + B² = C²

So to tell if it's inside the circle, get the x and y point of the hit, and the x and y values of the center of the circle. Then:

We get a triangle from the hit, to the center of the circle:

X -x == base distance of the triangle
Y - y == height distance of the triangle

Now base² + height² == hypotenuse² (distance as the crow flies), from the hit, to the center of the circle.

If hypotenuse is greater than the radius of the circle, then it's outside the circle. If it's less than or equal to, it's inside the circle.

For instance, if the triangle had base of 3, and height of 4, then the hypotenuse would be 5, since:
3² + 4² = 5²

So if the radius of the circle was > 5, the hit would be outside the circle. If it's less than or equal to 5, then it's inside it.

Quote:

---

Originally Posted by Adak

Actually, I was wondering if "tester" was BOTH a function, AND sometimes referred to the program "testing" in the simulation. It is confusing.

This is just the Pythagorean theorem:
RETURN 1 if sqrt(x*x + y*y) <= r, ELSE 0

Where x = A, y = B, and r = C² in A² + B² = C²

So to tell if it's inside the circle, get the x and y point of the hit, and the x and y values of the center of the circle. Then:

We get a triangle from the hit, to the center of the circle:

X -x == base distance of the triangle
Y - y == height distance of the triangle

Now base² + height² == hypotenuse² (distance as the crow flies), from the hit, to the center of the circle.

If hypotenuse is greater than the radius of the circle, then it's outside the circle. If it's less than or equal to, it's inside the circle.

For instance, if the triangle had base of 3, and height of 4, then the hypotenuse would be 5, since:
3² + 4² = 5²

So if the radius of the circle was > 5, the hit would be outside the circle. If it's less than or equal to 5, then it's inside it.

---

Ok, i think the function for DartHits works as is. Current code:

Code:

---

#include <stdio.h>
#define PI 3.14159
#define RADIUS 10


double RandNumInRange (double, double);


int main (void)
{
  int k;
  printf("Please enter a seed");
  scanf(%d, k);
  srand(k);
}


void GetBorders(double *xmin, double *xmax, double *ymin, double *ymax)
{
  double a, b, c, d;


  a = 27;
  b = 57;
  c = 33;
  d = 63;


  *xmin = a;
  *xmax = b;
  *ymin = c;
  *ymax = d;
}


double RandNumInRange (double z, double w) //where w is any max value, and z is any min value
{
  double rn;
  int i = 0;
  srand(1);


  while (i<1)
  {
    i++;
    rn = ((double)rand()/(double)RAND_MAX)*(w-z);
  }
return rn;
}


DartHits(double a, double b)
{
  double distance = sqrt(a*a + b*b);


  if (distance <= RADIUS)
  {
    return 1;
  }
  else
  {
    return 0;
  }
}


double ThrowDarts()
{
  double n;
  printf("How many darts would you like to throw?");
  scanf("&d", &llu);


  double xmax, xmin, ymax, ymin;
  GetBorders(&xmin, &xmax, &ymin, &ymax);
  double rectArea = (xmax -xmin) * (ymax - ymin);


  double xdart;
  double ydart;
  int i = 1;


//loop goes here:
while (i <= n)
  {
    double nhit;


    xdart = rand(xmin,xmax); //generate random number between xmin and xmax
      xdart = RandNumInRange(xmin,xmax);
   
    ydart = rand(ymin,ymax); //generate random number between ymin and ymax
      ydart = RandNumInRange(ymin,ymax);


    nhit = DartHits(xdart,ydart);
      if (nhit != 0)
        nhit++;
  }
  double estRectArea = rectArea * (nhit/n);
  return estRectArea;
}

---

Questions: How's everything look so far (is DartHits proper?) (minus formatting)
Rand still isn't working properly, and seed is entered by the user. Can srand be in main()? How do I pass N (number of hits, entered by user) to the ThrowDarts function?

P.S. are you available to use any form of Instant messenger? Trying to finish this tonight. If not I completely understand, do not want to be pressing in the least.

Ok disregard last post, most updated code with new questions:

Code:

---

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define PI 3.14159
#define RADIUS 10


double RandNumInRange (double, double);
double DartHits(double, double);
double ThrowDarts();


int main (void)
{


}


void GetBorders(double *xmin, double *xmax, double *ymin, double *ymax)
{
  double a, b, c, d;


  a = 27;
  b = 57;
  c = 33;
  d = 63;


  *xmin = a;
  *xmax = b;
  *ymin = c;
  *ymax = d;
}


double RandNumInRange (double z, double w) //where w is any max value, and z is any min value
{
  double rn;
 
  srand(1);
  rn = ((double)rand()/(double)RAND_MAX)*(w-z);


return rn;
}


double DartHits(double a, double b)
{
  double distance = sqrt(a*a + b*b);


  if (distance <= RADIUS)
  {
    return 1;
  }
  else
  {
    return 0;
  }
}


double ThrowDarts(double estRectArea)
{
  double n = 100;


  double xmax, xmin, ymax, ymin;
  GetBorders(&xmin, &xmax, &ymin, &ymax);
  double rectArea = (xmax -xmin) * (ymax - ymin);


  double xdart;
  double ydart;
  int i = 1;
  double nhit;


//loop goes here:
while (i <= n)
  {


    //generate random number between xmin and xmax
      xdart = RandNumInRange(xmin,xmax);
   
  //generate random number between ymin and ymax
      ydart = RandNumInRange(ymin,ymax);


    nhit = DartHits(xdart,ydart);
      if (nhit != 0)
      {
        nhit++;
      }
  }
  estRectArea = rectArea * (nhit/n);
  return estRectArea;
}

---

Things left to do: scanf seed number, pass it to rand, and make rand work.
pass n amount of hits to ThrowDarts function (pointers? if so, example?)
finally put it together and make the printout statements and properly format.

I'm am unsure how to do these things, but after this I'll be finished :D
It's due in ~18hrs from now. Thanks for all the help thus far, it's really helped a lot.

p.s nhits is a set number for now, until i figure out how to read it in and pass it to the ThrowDarts() function

srand should go out of your random function. high up in main would be good for it, because you only want to call it ONCE, and it must be early to be of any use. The scanf() for it, can be done right there.

int seed;

scanf("%d",&seed) and then srand(seed), should work OK. Rand doesn't need your seed number, unless your assignment requires it to be there. srand() works before rand, and "behind the scene", from rand.

Use your assignment requirements, but this might help your understanding:

Code:

---

#include <stdio.h>
#include <stdlib.h>


void getRandom(int mini,int maxi,int *rnumi, double min,double max,double *rnum, int type);

int main(void) {
  double xmin, xmax, ymin, ymax,rnum;
  int i, rnumi,xmini,xmaxi;

  srand(1);
  getRandom(0, 25,&rnumi,xmin,xmax,&rnum, 2);

  printf("\n");
  return 0;
}
void getRandom(int mini,int maxi,int *rnumi, double min,double max,double *rnum, int type) {
  int i;
 
  for(i=0,maxi=30;i<300;i++) {
      if(!type) { //get random ints
        *rnumi=rand() % maxi + mini+1;  //ints: range is mini - maxi
        printf("%5.2d  ",*rnumi);
      }
      else if(type==1) {
        *rnum = (double) (rand() % (int) (max +1)); //doubles: range is 1 - max, .00 numbers only   
        printf("%5.2f  ",*rnum);
      }
      else if(type==2) {
        *rnum = (double) rand()/(double) RAND_MAX; //doubles: range is 0 - 1. non-integral doubles (0.53,0.11, type numbers)
        printf("%5.2f  ",*rnum);
      }
     
     
  }
 
  printf("\n");
 
}

This allows both ints and doubles to be set to a random value, with the data type and range being determined by the "type" variable.

Only the rnumi (a rnum integer) or rnum (a double), is passed with a pointer (address only).

I'll look at the rest of it, in a couple hours. You have been busy! ;)

---

This is your program with a few tweaks. I haven't run it, but it (still) compiles.

Ask away if you have any questions or problems.

Code:

---

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define PI 3.14159
#define RADIUS 10
   
   
double RandNumInRange (double, double);
int DartHits(double, double);
double ThrowDarts(unsigned long *, double *, double *, double *, double *);
void analysis(double,unsigned long,double,double,double,double,double,
  double,double,double,unsigned long);
   
   
int main (void) {
  int seed;
  unsigned long N; //number of darts to be thrown
  double estRectArea;
  double lowx, lowy, hix, hiy; 
 
  printf("Enter the integer for the seed: ");
  scanf("%d",&seed);
  srand(seed);   
 
  estRectArea = ThrowDarts(&N,&lowx,&lowy,&hix,&hiy); 
  printf("\n");
  return 0;
}
void GetBorders(double *xmin, double *xmax, double *ymin, double *ymax) {
  double a, b, c, d;
   
  a = 27;
  b = 58;
  c = 3;
  d = 34;
   
  *xmin = a;
  *xmax = b;
  *ymin = c;
  *ymax = d;
}
double RandNumInRange (double z, double w) { //where w is any max value, and z is any min value
  double rn;
     
  rn = ((double)rand()/(double)RAND_MAX)*(w-z);
   
  return rn;
}
 
int DartHits(double x, double y) {
  double distance = sqrt(x*x + y*y);
   
  if (distance <= RADIUS) {
      return 1;
  }
  else {
      return 0;
  }
}
double ThrowDarts(unsigned long *N,double *lowx,double *lowy,double *hix,double *hiy) {
 
  printf("Enter the number of darts to be thrown in this simulation: ");
  scanf("%ul",N);
 
  double xmax, xmin, ymax, ymin;
  GetBorders(&xmin, &xmax, &ymin, &ymax);
  double rectArea = (xmax -xmin) * (ymax - ymin);
  double estRectArea = 0.0; 
  double xdart;
  double ydart;
  int i = 1;
  unsigned long nhit = 0; //hits can't be anything but integers
   
   
  //loop goes here:
  lowx=lowy=0;
  hix=hiy=0;
  while (i <= *N) {
      //generate random number between xmin and xmax
      xdart = RandNumInRange(xmin,xmax);
      if(xdart<*lowx)
        *lowx=xdart;
      if(xdart>*hix)
        *hix=xdart; 
      //generate random number between ymin and ymax
      ydart = RandNumInRange(ymin,ymax);
      if(ydart<*lowy)
        *lowy=ydart;
      if(ydart>*hiy)
        *hiy=ydart;

      if(DartHits(xdart,ydart)) {
        nhit++;
      }
  }
  estRectArea = rectArea * (nhit/ *N);
  return estRectArea;     
}
void analysis(double estRectArea, unsigned long N, double xmin,double xmax,double ymin,double ymax,
  double lowx,double lowy,double hix, double hiy, unsigned long nhits) { 
  double percentError = 0.0
  double error = 0;
  double actualArea = (ymax-ymin) * (xmax-xmin);
 
  printf("Rectange has length of %f and a width of %f\n",ymax-ymin,xmax-xmin);
  printf("Area of the rectangle is: %f\n",actualArea);
  printf("Darts thrown: %lu. Hits: %ul, hit percentage: %f%\n\n",N,nhits,(double)(nhits/N)*100);
 
  error = abs(actualArea - estRectArea);
  printf("Estimated Rectangular Area: %f Error in Area: %f\n",estRectArea,error);
 
  percentError = (error/actualArea) * 100;
  printf("Percent error was: %f%\n",percentError); 
}
/*  What Analysis function should do:
1. Length and width of enclosing rectangle
2. Area of enclosing rectangle
3. Number of darts thrown
4. How many darts hit the shape
5. Percentage of darts that hit the shape
6. Area of the shape computed by out dart throwing
7. Actual area of shape as known from an equation
8. The absolute value difference between these quantities (i.e., the error)
*/

---

well, getting segmentation fault errors. Even went to the cs tutor in which they couldn't help me. Spent 25+ hours on this. Really dissapointed. Heres my current code, somethigns wrong with n being a ul and then being used by a formula that wants a answer as a double. Also yhi, ylow, etc.. not sure if they even have values...


code:

Code:

---


#include <stdio.h>#include <stdlib.h>
#include <math.h>
#define PI 3.14159
#define RADIUS 10


double RandNumInRange (double, double);
int DartHits(double, double);
double ThrowDarts(unsigned long *, double *, double *, double *, double *);
void analysis(double estRectArea, unsigned long N, double xmin, double xmax, double ymin, double ymax,
  double lowx, double lowy, double hix, double hiy, double nhits);


int main (void) {
  int seed;
  unsigned long N; //number of darts to be thrown
  double estRectArea;
  double lowx, lowy, hix, hiy; 

  printf("Enter the integer for the seed: ");
  scanf("%d",&seed);
  srand(seed);   

  estRectArea = ThrowDarts(&N,&lowx,&lowy,&hix,&hiy); 
  printf("\n");
  return 0;
}
void GetBorders(double *xmin, double *xmax, double *ymin, double *ymax)
{
  double a, b, c, d;

  a = 27;
  b = 58;
  c = 3;
  d = 34;

  *xmin = a;
  *xmax = b;
  *ymin = c;
  *ymax = d;
}
double RandNumInRange (double z, double w)
{ //where w is any max value, and z is any min value
  double rn;

  rn = ((double)rand()/(double)RAND_MAX)*(w-z);

  return rn;
}

int DartHits(double x, double y) {
  double distance = sqrt(x*x + y*y);

  if (distance <= RADIUS) {
      return 1;
  }
  else {
      return 0;
  }
}
double ThrowDarts(unsigned long *N,double *lowx,double *lowy,double *hix,double *hiy) {

  printf("Enter the number of darts to be thrown in this simulation: ");
  scanf("%ld",&N);

  double xmax, xmin, ymax, ymin;
  GetBorders(&xmin, &xmax, &ymin, &ymax);
  double rectArea = (xmax -xmin) * (ymax - ymin);
  double estRectArea = 0.0; 
  double xdart;
  double ydart;
  int i = 1;
  double nhit = 0; //hits can't be anything but integers


  //loop goes here:
  *lowx=*lowy=0;
  *hix=*hiy=0;
  while (i <= N) {
      i++;
      //generate random number between xmin and xmax
      xdart = RandNumInRange(xmin,xmax);
      if(xdart<*lowx)
        *lowx=xdart;
      if(xdart>*hix)
        *hix=xdart; 
      //generate random number between ymin and ymax
      ydart = RandNumInRange(ymin,ymax);
      if(ydart<*lowy)
        *lowy=ydart;
      if(ydart>*hiy)
        *hiy=ydart;

      if(DartHits(xdart,ydart)) {
        nhit++;
      }
  }
  estRectArea = rectArea * (nhit/ *N);
  return estRectArea;     
}
void analysis(double estRectArea, unsigned long N, double xmin, double xmax, double ymin, double ymax,
  double lowx, double lowy, double hix, double hiy, double nhits)
{ 
  double percentError = 0.0;
  double error = 0;
  double actualArea = (ymax-ymin) * (xmax-xmin);

  printf("Rectangle has length of %f and a width of %f\n",ymax-ymin,xmax-xmin);
  printf("Area of the rectangle is: %f\n",actualArea);
  printf("Darts thrown: %ld. Hits: %f, hit percentage: %f%\n\n",N,nhits,((double)nhits/N)*100);

  error = abs(actualArea - estRectArea);
  printf("Estimated Rectangular Area: %f Error in Area: %f\n",estRectArea,error);

  percentError = (error/actualArea) * 100;
  printf("Percent error was: %f%\n",percentError); 
}
/*  What Analysis function should do:
1. Length and width of enclosing rectangle
2. Area of enclosing rectangle
3. Number of darts thrown
4. How many darts hit the shape
5. Percentage of darts that hit the shape
6. Area of the shape computed by out dart throwing
7. Actual area of shape as known from an equation
8. The absolute value difference between these quantities (i.e., the error)
*/

---

In ThrowDarts 'N' is a pointer and you are treating it like a normal variable.

For the seg fault - change these 2 things in ThrowDarts():

Code:

---

scanf("%ld",&N); //Remove '&' because the value in N is already "the address of" something
while (i <= *N)  //Dereference 'N', because 'N' is a pointer

---

ok fixed those, got this warning:

mcint2.c: In function ‘analysis’:
mcint2.c:111:4: warning: unknown conversion type character 0xa in format [-Wformat]
mcint2.c:117:4: warning: unknown conversion type character 0xa in format [-Wformat]


And when I compile it, I get:

Enter the integer for the seed: 10
Enter the number of darts to be thrown in this simulation: 20


Program stops after this. I think there is a problem with yhi, ylow, xhi, xlow... these are the same as xmax xmin ymin ymax? Except the hi's and lows don't actually have a variable..

Thanks so much for the help.

You should be receiving no warnings - if you are, something probably didn't get changed correctly.

lowy, lowx, hiy and hix are used to record the DART low and high values. xmin, ymin xmax and ymax are the actual BOX borders.

I'm not sure what you mean by "they don't actually have a variable".

I'll be looking at it some more, soon. See what it needs to run.

When is this due, in Pacific Daylight Time?

Exactly four hours from now. I think 10pm pacific. I live in U.S. central, its 8:00pm here, and its due at 12pm. And I think it has to do with N being read in as unsigned long int. I've tried fixing it, but I'm so gassed. Went to a tutor today that didn't even know data types. Lol.... But I do know the %ul wasn't working as a data type, but it recognized ul, ull, and i think ld. It's conflicting because we are using a long unsigned int in double estRectArea. Also, when I used a debugger that shows logic errors, it said estRectArea is never used... OR it said estRectArea never used by main()? Can't remember. Sorry I've given sloppy responses, I'm so gassed. Lost alot of sleep working on this past few days (lol). If there's one thing I know for sure, this goes back on the professor. We hadn't even learned about functions asn passing variables in c, but this was assigned. I figured a lot of stuff out on my own and using the book, but why should I pay for a course if the teacher isn't doing anything? I even skipped my classes today to work on this... Not angry, just dissapointed I REALLY thought I would have gotten this done earlier than today.. Oh well, learning experience right? /rant

Opps meant it recognised llu and lu. not ul and ull.

I'm tweaking a bunch of stuff up - there were errors ! :(

It's running now, but has some calculations still off. I'll post up the fix, in 40 minutes - 7:00 my time, 9:00 p.m. yours. Maybe rest until then?

Thank you so much! Your help is really appreciated, you have no clue. Seriously, not to go over bored, but I'm so humbled you've went out of your way to help someone on a forum.

Unfortunately, the program is still bonkers. Found out the ydart value is out of range (way too low), but have not fixed it.

Anyway:

Code:

---


#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define PI 3.14159
#define RADIUS 10
   
   
double RandNumInRange (double, double);
int DartHits(double, double);
double ThrowDarts(unsigned long *, double *, double *, double *, double *);
void analysis(double,unsigned long,double,double,double,double,double,
  double,double,double,unsigned long);
   
   
int main (void) {
  int seed;
  unsigned long N; //number of darts to be thrown
  double estRectArea;
  double lowx, lowy, hix, hiy; 
 
  printf("Enter the integer for the seed: ");
  scanf("%d",&seed);
  srand(seed);   
 
  estRectArea = ThrowDarts(&N,&lowx,&lowy,&hix,&hiy); 
  printf("\n");
  return 0;
}
void GetBorders(double *xmin, double *xmax, double *ymin, double *ymax) {
  double a, b, c, d;
   
  a = 27;
  b = 58;
  c = 3;
  d = 30;
   
  *xmin = a;
  *xmax = b;
  *ymin = c;
  *ymax = d;
}
double RandNumInRange (double z, double w) { //where w is any max value, and z is any min value
  double rn;
     
  rn = ((double)rand()/(double)RAND_MAX)*(w-z);
 
   
  return rn;
}
 
int DartHits(double x, double y) {
  double distance = sqrt(x*x + y*y);
   
  if (distance <= RADIUS) {
      return 1;
  }
  else {
      return 0;
  }
}
double ThrowDarts(unsigned long *N,double *lowx,double *lowy,double *hix,double *hiy) {
 
  printf("Enter the number of darts to be thrown in this simulation: ");
  scanf("%ul",N);
 
  double xmax, xmin, ymax, ymin;
  GetBorders(&xmin, &xmax, &ymin, &ymax);
  printf("\nCheck: xmax: %f, xmin: %f, ymax: %f, ymin: %f\n\n",xmax,xmin,ymax,ymin); getchar();

  double rectArea = (xmax -xmin) * (ymax - ymin);
  double estRectArea = 0.0; 
  double xdart;
  double ydart;
  int i = 1;
  unsigned long nhit = 0; //hits can't be anything but integers
   
  //loop goes here:
  *lowx=*lowy=1000;
  *hix=*hiy=0;
  //printf("
  while (i <= *N) {
      //generate random number between xmin and xmax
      xdart = RandNumInRange(xmin,xmax);
      printf("xdart: %f\n",xdart); getchar();
      if(xdart<*lowx)
        *lowx=xdart;
      if(xdart>*hix)
        *hix=xdart; 
      //generate random number between ymin and ymax
      ydart = RandNumInRange(ymin,ymax);
      printf("ydart: %f\n",ydart); getchar();
      if(ydart<*lowy)
        *lowy=ydart;
      if(ydart>*hiy)
        *hiy=ydart;

      if(DartHits(xdart,ydart)) {
        nhit++;
      }
      ++i;
  }
  printf("lowx: %f, lowy: %f, hix: %f, hiy: %f\n\n",*lowx,*lowy,*hix,*hiy); getchar();
  estRectArea = rectArea * (double) nhit/ *N;
  analysis(estRectArea, *N,xmin,xmax,ymin,ymax,*lowx,*lowy,*hix,*hiy,nhit);
 
  return estRectArea;  //no reason for this return, imo   
}
void analysis(double estRectArea, unsigned long N, double xmin,double xmax,double ymin,double ymax,
  double lowx,double lowy,double hix, double hiy, unsigned long nhit) { 
 
  double percentError = 0.0;
  double error = 0.0;
  double actualArea = (ymax-ymin) * (xmax-xmin);
 
  printf("Rectange has length of %.2f and a width of %.2f\n\n",ymax-ymin,xmax-xmin);
  printf("Area of the rectangle is: %.2f\n\n",actualArea);
  printf("Darts thrown: %lu. Hits: %lu, hit percentage: %.2f %%\n\n",N,nhit,(double)nhit/N*100);
 
  error = abs(actualArea - estRectArea);
  printf("Estimated Rectangular Area: %.2f Error in Area: %.2f\n\n",estRectArea,error);

  percentError = (error/actualArea) * 100;
  printf("Percent error was: %.2f %%\n",percentError);
}

---

I'm going to hunt down that ydart problem, asap. Just found out about it a few minutes ago.

I've got some debug helper print lines of code in there, which stop the program. Just hit enter to go to the next stopping point.

And thanks for bringing such an interesting (if a tad cryptic) problem. Of course, you're welcome.

If I get that ydart problem ID'd, I'll reply.

Sweet... Does this possibly have anything to do with it:

* Make start at particular value by adding starting value in
(will change ending value by same amount, so be prepared for that)

Part of the instruction for rand function. ^^

Quote:

---

Originally Posted by jsuite

Sweet... Does this possibly have anything to do with it:

* Make start at particular value by adding starting value in
(will change ending value by same amount, so be prepared for that)

Part of the instruction for rand function. ^^

---

Yes, it did. I've fixed that problem, but now hits is not registering correctly. I'll reply in 30 minutes. Wait for that.

ok! :D

I have the completed and functional code but will not post it until the 12 o'clock due time is over since I'm in the same CS 1713 class.

To show I'm not just pulling your chain here's part of the corrected code:

-Snipped code since people are sensitive to help-

Please note that this is not the fully corrected code and will not be compatible with the rest of the code you have posted beforehand.

Yes it is fully functional.

Not allowed to work with people in the same class on assignments, well at least on this one.

Quote:

---

Originally Posted by jsuite

Not allowed to work with people in the same class on assignments, well at least on this one.

---

Which is why I only posted half of the functional code instead of the full bulk of it.

I fixed half so that you can hopefully fix the other half on your own before the deadline.

I'm also in that class...does anyone understand how we are supposed to turn it in? I'm using Putty and don't get how to email it to her...

To actually copy the file, go to the path (as in go to my computer) and navigate to the file.

Unfortunately I can't use this because you're in my class. :(

Quote:

---

Originally Posted by seemethere

I have the completed and functional code but will not post it until the 12 o'clock due time is over since I'm in the same CS 1713 class.

To show I'm not just pulling your chain here's part of the corrected code:

Code:

---

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define PI 3.14159
#define RADIUS 20


/*
 * Comment syntax in C is /* as opposed to // in java
 * please remember that because it was quite annoying to
 * fix your code due to all of the //
 */     


/* Creating prototypes without "named" variables makes it very confusing
 * to fix your code */     
double RandNumInRange (double, double);
int DartHits(double, double);
/* Rebranded as void (does not need to return anything) */
void ThrowDarts(unsigned long *, double *, double *, double *, double *);
void analysis(double,unsigned long,double,
              double,double,double,unsigned long);
     
     
int main (void) {
  int seed;
  unsigned long N; /*number of darts to be thrown */
  double estRectArea;
  double lowx, lowy, hix, hiy; 
 
  printf("Enter the integer for the seed: ");
  scanf("%d",&seed);
  srand(seed);   
   
  ThrowDarts(&N,&lowx,&lowy,&hix,&hiy); 
  printf("\n");
  return 0;
}
void GetBorders(double *xmin, double *xmax, double *ymin, double *ymax) {
  /*double a, b, c, d;
     
  a = -30;
  b = 30;
  c = -30;
  d = 30; These are uneeded */
     
  *xmin = -30;
  *xmax = 30;
  *ymin = -30;
  *ymax = 30;
}
double RandNumInRange (double z, double w) { /*where w is any max value, and z is any min value*/
  int rn;
       
  rn = (rand() % (int)w + (int)z);
   
     
  return rn;
}


/* Linked our Prof to the thread - Contact Me if you'd like tutoring */

---

Please note that this is not the fully corrected code and will not be compatible with the rest of the code you have posted beforehand.

Yes it is fully functional.

---

That's quite a post! I wonder if you're aware that you have plagiarized his program, here?

And it's a matter of record by date and time of the post, that it belongs to the person with the handle of "jsuite".

I'm glad you got the program working, but you should receive an F for your plagiarism of his program. Continued plagiarism is cause for removal or suspension from the class, as well as from the school.

Schools of higher learning REALLY dislike people who steal the work of others, but you may discover that yourself, before long.

Thanks! I'll see if I can do that

tl;dr make a thread for help with class. Another student copies and pastes my code, makes it work for them, and tells me they linked prof to thread?

and then says to contact them for tutoring -_-

Just as a disclaimer:

I have my own program that I finished last week and turned in on Saturday before reading this post.

Thinking that I would plagiarize code for my own (especially one written with as many errors as this one) is asinine.

I am posting the code here merely as an exercise for troubleshooting and debugging on my own part.

So you're not a plagiarist, you're just using this as an stage to display your character and intellect. Well, the latter appears fine, the former appears deformed.

And for your info, // has been used for one line comments, since Turbo C/C++ ver. 1.01, which was copyrighted back in the late 1980's.

I'm merely trying to help jsuite with what is the style outlined for us in class.

I don't appreciate the hostility as I was just trying to help someone understand how to code independent of a forum.

to prove my code is independent of jsuite's
http://i.imgur.com/q0TXM.png

I will post jsuite's fully corrected code tomorrow morning purely for academic purposes.

Just PM it to me if you don't mind. :D

Quote:

---

Originally Posted by jsuite

Just PM it to me if you don't mind. :D

---

After you accused me of being plagiarist?

I already posted half of the corrected code with hints on how to fix the remainder of the code.

If you can't figure it out without us doing all of your homework then you don't deserve to finish it at all.

This forum is not about just doing code for someone else. It is about the collaborative learning experience.

Adak you are not helping jsuite by simply doing their code for them.

No I meant tomorrow, I already turned in the assignment a while ago out of frustration. Couldn't get out of an infinite loop, something was wrong with the while loop in ThrowDarts. So I'm not asking you to do my homework, I was saying instead of posting it in here tomorrow just PM it to me? And adak didn't do the assignment for me.

Btw the TA told me today that a lot of people turning it in won't be able to get the program to work properly (the ta in the comp lab) So you don't have to be so degrading and act like I have no clue what I'm doing.

jsuite has requested that this thread be deleted, but I am just going to close it because of the contributions made by others.

Quote:

---

Originally Posted by seemethere

I'm merely trying to help jsuite with what is the style outlined for us in class.

---

That's fine, though Adak does have a point in that your reasoning is factually incorrect since // has been the syntax for one line comments since the 1999 edition of the C standard.