Re: Can extra processing threads help in this case?

Hector Santos <>
Tue, 23 Mar 2010 01:39:18 -0400
Peter Olcott wrote:

"Hector Santos" <> wrote in message

Peter Olcott wrote:

Try running your process again using a
std::vector<unsigned int>
Make sure that you initialize all of this to the
subscript of the init loop.
Make sure that the process monitor shows that the amount
of memory you are allocating is the same amount that
total memory is reduced by.
Make sure that you only use 1/2 of total memory or less.
Make a not of the page fault behavior.
I will try the same thing.

Like I said, you better! I'm done!

I posted my code and my results. I ran it as a single
process and two separate processes, concurrently.
One process took 16.5 seconds of wall clock time.
Two concurrent processes took 16.55 seconds of wall clock
This proves that you were right all along.
Which means that my process will scale much better than I

I hear what you said and thats good that you think I am right, but you
didn't make it threaded, right.

The whole point of this exercise was to show each process you are
duplicating the std::vector allocation is putting pressure on the
system. By doing it one with X number of threads, you will see
different results.

Also, you had a line:

     num = data[num]

you were not referencing the entire spectrum of your memory
allocation, just one element.

I bet if you fix that to num=data[i], then you will see your problem
again with two instances.

If you want to change your code to make it threaded, change it to this
and play around with MAX_THREADS. Try 1, 2 4, etc and pay attention to:

    - Memory Load dispayed

and in Task Manager:

    - Working Set (memory usage)
    - Page Faults
    - Page Faults Delta
    - VM Size

There are all columns you can set via VIEW | Select Columns.

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#include <stdio.h>
#include <windows.h>
#include <stdlib.h>
#include <vector>
#include <time.h>
#include <conio.h>


#define uint32 unsigned int

const uint32 repeat = 1;
const uint32 size = 524288000 / 4;
std::vector<uint32> Data;

typedef struct _tagTThreadData {
    DWORD index;
    double duration;
} TThreadData;

TThreadData ThreadData[MAX_THREADS] = {0};

void WINAPI Process(TThreadData *data)
   clock_t finish;
   clock_t start = clock();
   uint32 num;
   for (uint32 r = 0; r < repeat; r++)
     for (uint32 i = 0; i < size; i++)
       num = Data[i];
   finish = clock();
   data->duration = (double)(finish - start) / CLOCKS_PER_SEC;

int main() {
   printf("Size in bytes--->%d\n", size * 4);
   for (int N = 0; N < size; N++)
     Data.push_back(rand() % size);

   char N;
   printf("Hit any key to Continue:");
   scanf("%c", &N);

     HANDLE hThreads[MAX_THREADS] = {0};
     DWORD tid;
     DWORD i;

     printf("* Starting threads\n");
     for(i=0;i < MAX_THREADS;i++){
         hThreads[i] = CreateThread(
                       (LPTHREAD_START_ROUTINE) Process,
                       (void *)&ThreadData[i],

     printf("* Wait For Thread Completion\n");

     while (WaitForMultipleObjects(MAX_THREADS, hThreads, TRUE, 100)
        if (_kbhit() && _getch() == 27) break;
        ms.dwLength = sizeof(ms);
        printf("- Memory Load: %d%%\r",ms.dwMemoryLoad);

     for (i = 0; i < MAX_THREADS; i++) {
        TThreadData dt = ThreadData[i];
        printf("%-3d | Time: %4.7f\n", i,dt.duration);

     printf("* Done\n");

  return 0;
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