Matrix Multiplication Speed Test (not runnable here - needs too much CPU time), C++ (vc++)

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#include <cmath>
#include <cstdlib>
#include <iostream>
#include <stdlib.h>
#include <assert.h>

using namespace std;

#define forall(i,n) for(int i=0; i<(int)(n); i++)

inline void Load(int N, int N2, float* x2, float* x, int iStart, int jStart) {
    int start = iStart * N + jStart;
    forall (i, N2)
        forall (j, N2)
            x2[i * N2 + j] = x[start + i * N + j];
}

inline void Add(int N, int N2, float* x, float* x2, int iStart, int jStart) {
    int start = iStart * N + jStart;
    forall (i, N2)
        forall (j, N2)
            x[start + i * N + j] += x2[i * N2 + j];
}

#ifndef UNROOL_LOOP
    #define UNROLL_LOOP 1
#endif

inline void Mul(int N, float* z, float* x, float* y) {
    forall (i, N)
        forall (j, N) {
            double sum = 0;
#if UNROLL_LOOP
            assert (N == 10);
            sum += x[i*N] * y[0*N+j];
            sum += x[i*N+1] * y[1*N+j];
            sum += x[i*N+2] * y[2*N+j];
            sum += x[i*N+3] * y[3*N+j];
            sum += x[i*N+4] * y[4*N+j];
            sum += x[i*N+5] * y[5*N+j];
            sum += x[i*N+6] * y[6*N+j];
            sum += x[i*N+7] * y[7*N+j];
            sum += x[i*N+8] * y[8*N+j];
            sum += x[i*N+9] * y[9*N+j];
#else
            forall (k, N)
                sum += x[i*N+k] * y[k*N+j];
#endif
            z[i*N+j] = sum;
        }
}

inline double RandReal() {return rand()/((double)RAND_MAX+1);}

#ifndef VAR
   #define VAR 0
#endif

#ifndef USE_STACK
    #define USE_STACK 0
#endif

int main(int argc, char** argv)
{
#if VAR==3
    int N = atoi(argv[1]), N2 = atoi(argv[2]);
#elif VAR==2
    const int N = 2000, N2 = atoi(argv[2]);
#elif VAR==1
    int N = atoi(argv[1]);
    const int N2 = 10;
#elif VAR==0
    const int N = 2000, N2 = 10;
#else
    #error "Bad VAR"
#endif
    cout << "\nVAR=" << VAR << " USE_STACK=" << USE_STACK << " N=" << N << ((VAR == 0 || VAR == 2) ? " (known)" : " (unknown)") << " N2=" << N2 << ((VAR == 0 || VAR == 1) ? " (known)" : " (unknown)") << endl;

#if USE_STACK  
    float x[N*N], y[N*N];
#else
    float *x = new float [N*N], *y = new float [N*N];
    assert (x && y);
#endif

forall (i, N)
        forall (j, N) {
            x[i*N+j] = RandReal();
            y[i*N+j] = RandReal();
        }

#if USE_STACK  
    float z[N*N];
#else
    float *z = new float [N*N];
    assert (z);
#endif

forall (i, N)
        forall (j, N)
            z[i*N+j] = 0;

#if !USE_STACK
    float *x2 = new float [N2*N2], *y2 = new float [N2*N2], *z2 = new float [N2*N2];
    assert (x2 && y2 && z2);
#endif

for (int i1 = 0; i1 < N; i1 += N2) {
#if USE_STACK  
        float x2[N2*N2], y2[N2*N2], z2[N2*N2];
#endif
        for (int j1 = 0; j1 < N; j1 += N2) {
            Load(N, N2, x2, x, i1, j1);
            for (int k1 = 0; k1 < N; k1 += N2) {
                Load(N, N2, y2, y, j1, k1);
                Mul(N2, z2, x2, y2);
                Add(N, N2, z, z2, i1, k1);
            }
        }
    }

double val = 0, val2 = 0;
    forall (i, N)
        forall (j, N)
            val += z[i*N+j], val2 += z[i*N+j]*(i+j);
    cout << "val=" << val << " val2=" << val2 << endl;
}

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Compilation time: 1,73 sec, absolute running time: 20,19 sec, absolute service time: 21,93 sec

Matrix Multiplication Speed Test (not runnable here - needs too much C...