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POHelp with a copy between buffers using memcpy C
 

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  1. POHelp with a copy between buffers using memcpy C
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    <p>I need to copy the content of one buffer to another one in blocks of <em>n</em> bytes (<em>n</em> might vary), several times to check the cache performance.</p> <p>I use memcpy, but I'm afraid I'm not getting successful results. The block size is variable from some kbytes to Mbytes. And I have to reserve the maximum block to use (long double).</p> <p>I'm a little lost in the copy. I'm just wondering if somebody has faced this problem, and can help me with some tips or pseudo code.</p> <p>I edit the topic to include some code:</p> <pre><code>int main (int argc, char *argv[]) { FILE *fp; fp= fopen("part1.dat", "w"); struct timeval time, oldtime; float segundos, microsegundos, total; // float rendimiento; pid_t pid; struct sched_param parametros; int i, v,p; char buffer1[100024]; char buffer2[100024]; pid = getpid(); parametros.sched_priority = sched_get_priority_max(SCHED_FIFO); sched_setscheduler(pid, SCHED_FIFO, &amp;parametros); p=0; gettimeofday(&amp;oldtime, NULL); for (i=1;i&lt;65;i++) { size_t datos=i*1024; for (v=0; p&gt;i;v++) { memcpy(buffer1, buffer2, datos); p=(MAX_SIZE/i*1024); } } gettimeofday(&amp;time, NULL); segundos = (float) (time.tv_sec - oldtime.tv_sec); microsegundos = (float) (time.tv_usec - oldtime.tv_usec); total = (float) ((segundos * 1000000 + microsegundos)); // printf ("Dimension %d \t Tiempo 1: %.2f \t Fallos Metodo 1:%d \t Tiempo 2: %.2f \t Fallos Metodo 2:%d \t Multiplica: %f \t Rendimiento: %.2f\n", i, total, fallos1, total2, fallos2, iteraciones, rendimiento); // fprintf (fp, "%d \t %.3f %.3f %.3f\n", i, total, total2,rendimiento); fclose(fp); printf("Se ha creado el archivo de datos: part1.dat\n"); return(0); } </code></pre> <p>The idea is to copy from buffer1 to buffer2, in datos blocks 'p' times, in this case is supposed to be done 256000 times (i=1, datos=1024).</p>
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    1. USIsak Savo
    1. USPeter
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    1. COYou don't really explain what you are having trouble doing? Are you having trouble getting 'blocks' to copy between? call malloc(). Are you having trouble measuring the time taken? you'll need to tell us what platform if you want <1ms accuracy.
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      1. POHelp with a copy between buffers using memcpy C
      1. USChris Becke
    2. COYes, I'm sorry for not being so clear, I don't know exactly where is the fault. I define two buffer (char *buff[n]) and then the data block array (long double block[]), then I just want to copy a block of data from one buffer to another 'x' times. For example if the block is 1024 bytes, do the copy 10 times.
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      1. POHelp with a copy between buffers using memcpy C
      1. USPeter
    3. COBut you know there is a fault. What are the symptoms? What happens or happens not? Can you show us some code? How far are you? Or do you have trouble with writing a for-loop?
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      1. POHelp with a copy between buffers using memcpy C
      1. USSecure
 

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