help with strategy to tackle a project

Hello,

I am hoping someone may have a suggestion as to what is the best way to do what I need to do.

I am writing a program to simulate a physical system. The simplest analogy of what I need to do would be to simulate random walkers flowing down a tube. This, in itself, is relatively easy. However, there are two complicating factors. First, I need to generate new random walkers at regular intervals (of simulated time) at one end of the tube. Second, I need to monitor them while they are inside the tube, and then forget about them when they exit through the other end of the tube.

The way I would do it is with a vector of structs (sloppy code follows)

Code:

---

typedef struct _walkerType
{
    ... stuff I need for the walkers ...
    int      activeFlag;
} walkerType;

std::vector< walkerType > walkers;

---

And then, down in the code

Code:

---

if ( time_is_right )
{
    generateRandomInitialWalker();        // call it walker0, with activeFlag = 1
    walkers.push_back(walker0)
}

for ( i=0; i<walkers.size(); i++ )
{
    if ( walkers[i].activeFlag )
    {
        do_stuff();
    }

    if ( reach_other_end )
    {
        walker[i].activeFlag = 0;
    }
}

time += delta_time;

---

While I think this would work, I can see two big problems.

1) After a while of running, most of the walkers would be inactive, yet I still have to loop through them

2) the vector could potentially become huge, gulping loads of memory.

Does anyone have any suggestion as to a better way to implement this?

Thanks a lot,

mc61

Quote:

---

Originally Posted by mc61

Hello,

I am hoping someone may have a suggestion as to what is the best way to do what I need to do.

I am writing a program to simulate a physical system. The simplest analogy of what I need to do would be to simulate random walkers flowing down a tube.

---

Does the ordering of walkers remain constant? i.e., is this a first in, first out tube? If so, there is a standard container that would be a better choice than std::vector (hint).

Also, I'd consider a container of smart pointers (like boost::shared_ptr) instead of a container of objects, unless you don't mind all of the copying.

No, the walkers will exit the tube at a different order than they were created.

While I have a little experience in C, I am totally new to C++. Could you tell me where I could read about the smart pointers you talk about?

Thanks,

mc61

Quote:

---

Originally Posted by mc61

No, the walkers will exit the tube at a different order than they were created.

While I have a little experience in C, I am totally new to C++. Could you tell me where I could read about the smart pointers you talk about?

---

http://boost.org/doc/libs/1_35_0/lib.../smart_ptr.htm

TR1 implementations also have boost's smart pointers, so if you use a compiler with TR1 support (Visual Studio 2008 Professional or GCC I would believe, among some), you could that as well (std::tr1::shared_ptr, for example).

Quote:

---

Originally Posted by mc61

While I think this would work, I can see two big problems.

1) After a while of running, most of the walkers would be inactive, yet I still have to loop through them

2) the vector could potentially become huge, gulping loads of memory.

---

Back to this part of the problem, you can erase (remove) elements from standard containers.

Thanks for all the suggestions. I am just learning how to erase elements from standard containers, together with a few other things you can do with them that I did not know. I think I'll manage.

Thanks again,

mc61