C codes takes more timing cycles_Better OPTIMIZATION for Codes

**SarasMuthu** · 07-31-2017

Hi,

It takes more timing cycles.

Starts at 46 clock cycles but execution continues for 678 clock cycles. Trying to reduce execution time. Please modify codes.

Code:

 #include <stdio.h>

    int main()
   {
    int n,r,c,no_e,S;
    int y[6] = {0};

    int i,j,pos,I;
    int Imax = 20;
    int E[4][6] = {0};
    int H[4][6] = {1,1,0,1,0,0,0,1,1,0,1,0,1,0,0,0,1,1,0,0,1,1,0,1};
    int M[6] = {0,0,1,-1,-1,-1};
    n = 6;
    r = 4;
    c = 6;
//Decoding using Message passing in Erasure channel
    no_e = 0;
    S = 0;
    pos = 0;
    I = 0;
    for(j=0;j<r && I<Imax;j++)
    {
        for(i=0;i<n;i++)
        {
            if(H[j][i] == 1)
            {
                if(M[i] < 0)
                {
                    no_e = no_e + 1;
                    pos = i;        //The position of erasure bit
                }
                    if(M[i] == 0 || M[i] == 1)
                    S = S + M[i];
            }
        }
            if(no_e > 1)
             for(i=0;i<n;i++)
                E[I][i] = -1;       //Make the entire jth row -1
        else
            for(i=0;i<n;i++)
                E[I][i] = M[i];
        if(no_e == 1)
        {
            E[I][pos] = S%2;      // Set the bit with the correct value
            M[pos] = S%2;         //Replace the bit with the corrected  
        }

        no_e = 0;
        S = 0;

        for(i=0;i<n;i++)
            if(M[i]<0)
                no_e = no_e+1;  
        if(no_e == 0)
            break;

        I = I + 1;
        no_e = 0;
        if(j==r-1)
            j=0;   
     }

     printf("\n\n\nThe corrected Code Word is(%d): \n\n",I);
     for(i=0;i<n;i++)
        printf("%d\t",M[i]);
    }

**Salem** · 07-31-2017

Is that with or without the printf statements at the end?

Also, does that time include the time it takes the OS to load your program, and then for the C runtime system to initialise itself before it even gets to calling main?

Also, does that time include any time spent inside interrupt service routines which may happen while your program is running?

Also, did you make use of any compiler optimisation flags?

How about compiling it with more warnings?

Code:

$ gcc -Wall foo.c
foo.c: In function ‘main’:
foo.c:11:17: warning: missing braces around initializer [-Wmissing-braces]
   int H[4][6] = { 1, 1, 0, 1, 0, 0, 0, 1, 1, 0, 1, 0, 1, 0, 0, 0, 1, 1, 0, 0, 1, 1, 0, 1 };
                 ^
foo.c:11:17: note: (near initialization for ‘H’)
foo.c:10:7: warning: variable ‘E’ set but not used [-Wunused-but-set-variable]
   int E[4][6] = { 0 };
       ^
foo.c:6:7: warning: unused variable ‘y’ [-Wunused-variable]
   int y[6] = { 0 };
       ^
foo.c:5:13: warning: variable ‘c’ set but not used [-Wunused-but-set-variable]
   int n, r, c, no_e, S;
             ^

That E thing is a killer for you.
There's a whole bunch of code dedicated to setting E which serves no purpose whatsoever.

Code:

#include <stdio.h>

int main()
{
  int n, r, no_e, S;
  //!!int y[6] = { 0 };

  int i, j, pos, I;
  int Imax = 20;
  //!!int E[4][6] = { 0 };
  int H[4][6] = {
    { 1, 1, 0, 1, 0, 0 },
    { 0, 1, 1, 0, 1, 0 },
    { 1, 0, 0, 0, 1, 1 },
    { 0, 0, 1, 1, 0, 1 },
  };
  int M[6] = { 0, 0, 1, -1, -1, -1 };
  n = 6;
  r = 4;
  //!! c = 6;
//Decoding using Message passing in Erasure channel
  no_e = 0;
  S = 0;
  pos = 0;
  I = 0;
  for (j = 0; j < r && I < Imax; j++) {
    for (i = 0; i < n; i++) {
      if (H[j][i] == 1) {
        if (M[i] < 0) {
          no_e = no_e + 1;
          pos = i;              //The position of erasure bit
        }
        if (M[i] == 0 || M[i] == 1)
          S = S + M[i];
      }
    }
//!!     if (no_e > 1)
//!!       for (i = 0; i < n; i++)
//!!         E[I][i] = -1;           //Make the entire jth row -1
//!!     else
//!!       for (i = 0; i < n; i++)
//!!         E[I][i] = M[i];
    if (no_e == 1) {
//!!       E[I][pos] = S % 2;        // Set the bit with the correct value
      M[pos] = S % 2;           //Replace the bit with the corrected
    }

    no_e = 0;
    S = 0;

    for (i = 0; i < n; i++)
      if (M[i] < 0)
        no_e = no_e + 1;
    if (no_e == 0)
      break;

    I = I + 1;
    no_e = 0;
    if (j == r - 1)
      j = 0;
  }

  printf("\n\n\nThe corrected Code Word is(%d): \n\n", I);
  for (i = 0; i < n; i++)
    printf("%d\t", M[i]);
  printf("\n");
}

And still, you fail to provide details of your ALGORITHM. The single useful comment in your code suggests you're up to something to do with error detection and recovery.
Erasure channel - Wikipedia

It's like if you implemented bubble sort, then the best we could come up with is a slightly better bubble sort. But the real answer would be to throw the code away and implement quicksort.

**SarasMuthu** · 07-31-2017

Thanks for your response. Working with message passing. For ALGORITHM click [link] []SPM: 404 Page Not Found.

-1 indicates the missed/Erasure bit. Then how to executes the codes. Please help and guide me.

**Hodor** · 07-31-2017

"codes"?

**SarasMuthu** · 07-31-2017

Originally Posted by Hodor

"codes"?

What you telling ?

**SarasMuthu** · 07-31-2017

Hi,

If you see the attachment, first loop takes more time. Any optimization method ? welcome

Code:

    for(j=0;j<ROWS && I<Imax;j++)
    {

        for(i=0;i<COLS;i++)

        {

            if(matrix[j][i] == 1)
            {

                if(M[i] < 0)
                {

                    no_e = no_e + 1;
                    pos = i;        //The position of erasure bit
                }
                if(M[i] == 0 || M[i] == 1)
                    S = S + M[i];
            }
        }
        if(no_e > 1)
            for(i=0;i<n;i++)


                E[I][i] = -1;       //Make the entire jth row -1
        else
            for(i=0;i<n;i++)

                E[I][i] = M[i];
        if(no_e == 1)
        {

            E[I][pos] = S%2;      // Set the bit with the correct value
            M[pos] = S%2;         //Replace the bit with the corrected bit before further proceeding
        }

        for(i=0;i<n;i++)


            if(M[i]<0)
                no_e = no_e+1;     // Calculating no of errors in entire message

        if(no_e == 0)
            break;

        I = I + 1;
        no_e = 0;
        if(j==ROWS-1)
            j=0;                   
    }

**Salem** · 07-31-2017

Well you haven't addressed what the E array is for.
It's still unused as far as I'm concerned.

> M[pos] = S%2;
On the off chance that your compiler is too stupid to replace this with
M[pos] = S & 1;
perhaps you could do it yourself.

Are you turning optimisations on before doing timing tests?

> if(M[i] == 0 || M[i] == 1)
Having already established that M[i] isn't less than zero, perhaps
else if(M[i] <= 1)

**algorism** · 07-31-2017

Originally Posted by SarasMuthu

What you telling ?

Hodor was tittering at the dearth of linguistic perspicacity you exhibit vis a vis English.

Anyway, it seems unlikely to me that your code is even correct. You should work on that first. Remember to maximize your warning level and fix all warnings.

Thread: C codes takes more timing cycles_Better OPTIMIZATION for Codes

Thread Tools

Search Thread

Display

C codes takes more timing cycles_Better OPTIMIZATION for Codes

Similar Threads

Validate area codes within a list of area codes

help me with C codes

c codes need help,thanks

VK codes

converting scan codes to ascii codes

Tags for this Thread