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threaded_Mat_Mul.c
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threaded_Mat_Mul.c
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/*
============================================================================
Name : threaded_Mat_Mul.c
Author : Ashraf Saleh
Version :
Copyright : refer to my blog
Description : Mutlithreaded Matrix Multiplication C, Ansi-style
============================================================================
*/
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <math.h>
//matrix a is m*p while b is q*n
// c is m*n m rows, n cols
int m,p,q,n;
int **a, ** b, **c;
struct timeval tv;
long long curTime(){
gettimeofday(&tv,NULL);
return tv.tv_usec;
}
void *mulrow(void* row);
void *mulcell(void* row);
void print(int** a,int _i, int _j){
int i,j;
for (i = 0; i < _i; ++i) {
for (j = 0; j < _j; ++j)
printf("%d\t",a[i][j]);
printf("\n");
}
}
void writeMat(int** a,int _i, int _j, FILE* f){
int i,j;
for (i = 0; i < _i; ++i) {
for (j = 0; j < _j; ++j)
fprintf(f,"%d ",a[i][j]);
fprintf(f,"\n");
}
}
void multiply(int** a , int** b, int** c){
int i,j,k;
for (i = 0; i < m; ++i) {
for ( j = 0; j < n; ++j) {
for (k = 0; k < q; ++k) {
c[i][j] += (a[i][k]) * (b[k][j]);
}
}
}
}
struct cell{int i,j;};
void multiply1(){
// The computation of each element of the output matrix happens in a thread.
int i,j,r,t;
//dynamically allocate #cells threads
pthread_t** threads = (pthread_t**) malloc(sizeof(pthread_t*)*m*n);
struct cell** cells = (struct cell**) malloc(sizeof(struct cell*)*m*n);
for (i = 0; i < m; ++i) {
for (j = 0 ; j < n ; j ++){
t = i*n + j;
threads[t] =(pthread_t*) malloc(sizeof(pthread_t));
cells[t] = malloc(sizeof(struct cell));
cells[t]->i = i ; cells[t]->j = j;
r = pthread_create(threads[t], NULL, mulcell, (void*) cells[t]);
if (r<0)
printf("failed to create thread at mul1 at (i,j) %d,%d\n",i,j);
}
}
//wait for the threads to finish
for (i = 0; i < m*n; ++i){
pthread_join(*threads[i],NULL);
free(cells[i]);
// no need to free threads[i] as its already freed by pthread_exit();
}
//free allocated memory
free(threads);
free(cells);
}
void *mulcell(void* param){
// passing a struct to overcome the limitation of passing one argument
struct cell *cel = (struct cell*)param;
int k, i = cel->i, j = cel->j;
for (k = 0; k < p; ++k){
c[i][j] += a[i][k] * b[k][j];
}
pthread_exit(0);
return NULL;//will never execute
}
void multiply2(){
//The computation of each row of the output matrix happens in a thread.
int i,r;
//dynamically allocate #rows threads
pthread_t** threads = (pthread_t**) malloc(sizeof(pthread_t*)*m);
int* rows = (int*) malloc(sizeof(int)*m);
for (i = 0; i < m; ++i) {
threads[i] =(pthread_t*) malloc(sizeof(pthread_t));
rows[i] = i;
r = pthread_create(threads[i], NULL, mulrow, (void*) &rows[i]);
if (r<0)
printf("failed to create thread at mul2 at i = %d\n",i);
}
//wait for the threads to finish
for (i = 0; i < m; ++i)
pthread_join(*threads[i],NULL);
//free allocated memory
free(threads);
free(rows);
}
void *mulrow(void* row){
int j, i = *((int*)row) ,k;
for (j = 0 ; j < n ; j ++)
for (k = 0 ; k < p ; k++)
c[i][j] += a[i][k] * b[k][j];
pthread_exit(NULL);
return NULL;// anyway this line won't be processes yet it's added to prevent eclipse from showing warnings
}
int **read_matrix(FILE *f,int m, int n){
int i,j;
int **a = (int**) malloc(sizeof(int *)*m);
for (i = 0; i < m; ++i) {
a[i] = (int *) malloc(sizeof(int)*n);
for (j = 0; j < n; ++j) {
fscanf(f,"%d",&a[i][j]);
}
}
return a;
}
long long benchmark(int nElements, int itrNum , void(*myfn)()){
n = m = p = nElements;
a = (int**) malloc(sizeof(int*)*nElements);
b = (int**) malloc(sizeof(int*)*nElements);
c = (int**) malloc(sizeof(int*)*nElements);
int i,j,k;
long long averagetime =0 ,t1,t2;
for (i = 0; i < nElements; ++i){
a[i] = (int*) malloc(sizeof(int)*nElements);
b[i] = (int*) malloc(sizeof(int)*nElements);
c[i] = (int*) malloc(sizeof(int)*nElements);
}
for (k = 0; k < itrNum; ++k) {
for (i = 0; i < nElements; ++i)
for (j = 0; j < nElements; ++j)
a[i][j] =rand()%1001 , b[i][j] =rand()%1001;
t1 = curTime();
// multiply1();
(*myfn)();
t2 = curTime();
averagetime += (t2-t1);
}
print(c,nElements,nElements);
averagetime/=itrNum;
printf("benchmark using a[%d][%d] * b[%d][%d]: average on %d samples = %lld usec\n",
nElements,nElements,nElements,nElements,itrNum,averagetime);
return averagetime;
}
int main(void) {
benchmark(400,1,multiply2);
int i,j;
FILE* in = fopen("input.txt","r");
// reading matrix a
fscanf(in,"%d %d",&m,&p);
a = read_matrix(in,m,p);
// reading matrix b
fscanf(in,"%d %d",&q,&n);
b = read_matrix(in,q,n);
if (p!=q){
printf("incompatible matrices --not supported\n");
return 0;
}
//initializing matrix c
c = (int**) malloc(sizeof(int *)*m);
for (i = 0; i < m; ++i){
c[i] = (int *) malloc(sizeof(int)*n);
for (j = 0; j < n; ++j)
c[i][j] = 0;
}
long long t1,t2;
FILE* out = fopen("output.txt","w");
// multiply(a,b,c);
// multiply(a,b,c);
// multiply(a,b,c);
for (i = 0; i < m; ++i)
for (j = 0; j < n; ++j)
c[i][j] = 0;
fprintf(out,"result of non-threaded multiplication\n");
t1 = curTime();
multiply(a,b,c);
t2 = curTime();
writeMat(c,m,n,out);
fprintf(out,"elapsed time = %lld usec\n\n",t2-t1);
for (i = 0; i < m; ++i)
for (j = 0; j < n; ++j)
c[i][j] = 0;
fprintf(out,"result of multiplication1 (thread for each cell)\n");
t1 = curTime();
multiply1();
t2 = curTime();
writeMat(c,m,n,out);
fprintf(out,"elapsed time = %lld usec\n\n",t2-t1);
for (i = 0; i < m; ++i)
for (j = 0; j < n; ++j)
c[i][j] = 0;
fprintf(out,"result of multiplication2 (thread for each row)\n");
t1 = curTime();
multiply2();
t2 = curTime();
writeMat(c,m,n,out);
fprintf(out,"elapsed time = %lld usec\n\n",t2-t1);
fclose(out);
print(c,m,n);
return 0;
}