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loop.c
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loop.c
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/* Anything may be changed, except matrix sizes and float type.
*
* The output when defining CHECK should be the same with and without tuning.
*
*/
#include <stdio.h>
#include <string.h>
#include <sys/time.h>
// #define CHECK
#define I (10000)
#define S (10)
#define B (20)
#define MIN(X,Y) ((X) < (Y) ? (X) : (Y))
#ifdef CHECK
#define TYPE int
#define N (3)
#else
#define TYPE float
#define N (512)
#endif
TYPE a[N][N];
TYPE b[N][N];
TYPE c[N][N];
/**
Original
**/
void f0()
{
size_t i, j, k;
for (i = 0; i < N; i += 1) {
for (j = 0; j < N; j += 1) {
a[i][j] = 0;
for (k = 0; k < N; k += 1)
a[i][j] += b[i][k] * c[k][j];
}
}
}
/**
Rearanged the loops
**/
void f1()
{
size_t i, j, k;
for (i = 0; i < N; i += 1) {
memset(a[i], 0, N);
for (k = 0; k < N; k += 1){
for (j = 0; j < N; j += 1) {
a[i][j] += b[i][k] * c[k][j];
}
}
}
}
/**
Rearanged the loops
Extracted b[i][k]
Unraveled loop
**/
void f2()
{
size_t i, j, k;
int bik;
for (i = 0; i < N; i += 1) {
memset(a[i], 0, N);
for (k = 0; k < N; k += 1){
bik = b[i][k];
for (j = 0; j < N-1; j += 2) {
a[i][j] += bik * c[k][j];
a[i][j+1] += bik * c[k][j+1];
}
for (; j < N; j += 1) {
a[i][j] += bik * c[k][j];
}
}
}
}
/**
Rearanged the loops
Extracted b[i][k]
Unraveled loop
Using pointers instead
**/
void f3()
{
size_t i, j, k;
TYPE* bi;
TYPE* ai;
TYPE* ck;
for (i = 0; i < N; i += 1) {
memset(a[i], 0, N);
bi = b[i];
for (k = 0; k < N; k += 1){
ai = a[i];
ck = c[k];
for (j = 0; j < N-2; j += 3) {
*ai++ += *bi * *ck++;
*ai++ += *bi * *ck++;
*ai++ += *bi * *ck++;
}
for (; j < N; j += 1) {
*ai += *bi * *ck;
}
bi++;
}
}
}
/**
Rearanged the loops
Tiling
**/
void f4()
{
size_t i, j, k;
size_t jj, kk;
memset(a, 0, sizeof a);
for(kk = 0; kk < N; kk += B){
for(jj = 0; jj < N; jj += B){
for (i = 0; i < N; ++i) {
for (k = kk; k < MIN(N, kk+B); ++k){
for (j = jj; j < MIN(N, jj+B); ++j) {
a[i][j] += b[i][k] * c[k][j];
}
}
}
}
}
}
void init()
{
#ifdef CHECK
size_t i, j;
for (i = 0; i < N; i += 1) {
for (j = 0; j < N; j += 1) {
b[i][j] = 12 + i * j * 13;
c[i][j] = -13 + i + j * 21;
}
}
#endif
}
void output()
{
#ifdef CHECK
size_t i, j;
for (i = 0; i < N; i += 1)
for (j = 0; j < N; j += 1)
printf("a[%3zu][%3zu] = %d\n", i, j, a[i][j]);
#endif
}
void (*fun[])() = {
f0,
f1,
f2,
f3,
f4
};
/* Return 1 if the difference is negative, otherwise 0. */
int timeval_subtract(struct timeval *result, struct timeval *t2, struct timeval *t1)
{
long int diff = (t2->tv_usec + 1000000 * t2->tv_sec) - (t1->tv_usec + 1000000 * t1->tv_sec);
result->tv_sec = diff / 1000000;
result->tv_usec = diff % 1000000;
return (diff<0);
}
int main(void)
{
size_t i;
size_t j;
struct timeval tvBegin, tvEnd, tvDiff;
for (j = 0; j < sizeof fun/sizeof fun[0]; ++j) {
memset(a, 0, sizeof a);
gettimeofday(&tvBegin, NULL);
for (i = 0; i < I; ++i)
init();
fun[j]();
gettimeofday(&tvEnd, NULL);
output();
timeval_subtract(&tvDiff, &tvEnd, &tvBegin);
printf("%ld.%06ld s\n", tvDiff.tv_sec, tvDiff.tv_usec);
}
}