Time.c

/*
File:  Time.c
 
Abstract:
    This program times some cases of the vAdd routine.  It illustrates the
    execution speed of the sample routine but is not otherwise needed to
    understand the lessons of the session.
 
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*/
 
 
#include <stdio.h>
#include <stdlib.h>
 
#include "ClockServices.h"
#include "vAdd.h"
 
 
#define ElementsPerVector   4
 
 
// Define a structure to hold parameters needed by the routine being timed.
typedef struct { const float *A; const float *B; float *C; long N; } Parameters;
 
 
// Driver is a routine that calls the subject routine repeatedly.
void Driver(unsigned int iterations, void *data)
{
    // Get the parameters from the structure passed to us.
    Parameters *parameters = (Parameters *) data;
 
    const float *A  = parameters->A;
    const float *B  = parameters->B;
          float *C  = parameters->C;
    long N = parameters->N;
 
    // Call the subject routine the number of times requested.
    while (iterations--)
        vAdd(A, B, C, N);
}
 
 
int main(void)
{
    // Define test data.
    static const int N = 1024;
    int AllocationLength = N + ElementsPerVector - 1;
 
    /*  Allocate space for arrays.  Include extra space so we can perform
        measurements with different address offsets.
    */
    float *A = malloc(AllocationLength * sizeof *A);
    float *B = malloc(AllocationLength * sizeof *B);
    float *C = malloc(AllocationLength * sizeof *C);
    if (!A || !B || !C)
    {
        free(C);
        free(B);
        free(A);
        fprintf(stderr, "Error, failed to allocate memory.\n");
        return EXIT_FAILURE;
    }
 
    // Initialize input arrays.
    for (long i = 0; i < AllocationLength; ++i)
    {
        A[i] = i;
        B[i] = 10000 * i;
    }
 
    // Print table header.
    printf("Offset in Bytes\n");
    printf("   A    B    C    CPU Cycles Per Element\n");
 
    for (long AOffset = 0; AOffset < ElementsPerVector; ++AOffset)
    for (long BOffset = 0; BOffset < ElementsPerVector; ++BOffset)
    for (long COffset = 0; COffset < ElementsPerVector; ++COffset)
    {
        // Package parameters for timing routine.
        Parameters parameters = { A + AOffset, B + BOffset, C + COffset, N };
 
        // Measure the execution time of the subject routine.
        double t = MeasureNetTimeInCPUCycles(Driver, 100, &parameters, 100);
 
        printf("%4zd %4zd %4zd    %.3g\n",
            AOffset * sizeof *A, BOffset * sizeof *B, COffset * sizeof *C,
            t / N);
    }
 
    free(C);
    free(B);
    free(A);
 
    return 0;
}