Ansi C, Multithreading MatrixMultiplication - c

Question

I have been programming this multiplethreaded matrix multiplication.
Somehow the programm works, but it does not give me the values of the result matrix.
Here it is the code:
#include <stdio.h>
#include <pthread.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
int rowA, rowB, colA, colB;
int myNrThreads = 0;
double **matrixA, **matrixB, **matrixOut;
void *multiplyThread (void *param);
void fillAndCheckMatrice(double **matrix, FILE *myFile, int row, int column) {
char *line = NULL;
char *p;
ssize_t read;
int i = 0, j = 0;
size_t length = 0;
getline (&line, &length, myFile);
p = strtok(line, " ");
row = atoi(p);
p = strtok(NULL, " ");
column = atoi(p);
printf("%d, %d\n", row, column);
matrix = malloc(row * sizeof(double*));
for (j = 0; j < row; ++j) {
matrix[j] = malloc(column * sizeof(double));
}
i = 0;
while ((read = getline (&line, &length, myFile)) != -1) {
j = 0;
p = strtok(line, " ");
while (p != NULL) {
matrix[i][j] = atof(p);
++j;
p = strtok(NULL, " ");
}
++i;
}
free(line);
}
int main (int argc, char* argv[])
{
pthread_t *myThread;
int counter, j, r;
FILE *fileA = fopen("matrixA.txt", "r");
FILE *fileB = fopen ("matrixB.txt", "r");
if (argc!=2)
{
printf("Usage: %s number_of_threads\n",argv[0]);
exit(-1);
}
myNrThreads = (atoi)(argv[1]);
fillAndCheckMatrice(matrixA, fileA, rowA, colA);
fillAndCheckMatrice(matrixB, fileB, rowB, colB);
matrixOut = malloc(rowA * sizeof(double*));
for (counter = 0; counter < rowA; ++counter) {
matrixOut[counter] = malloc (colB * sizeof(double));
}
myThread = malloc(myNrThreads * sizeof(pthread_t));
for (counter = 1; counter < myNrThreads; ++counter) {
r = pthread_create (&myThread[counter], NULL, multiplyThread, (void*)counter);
if (r != 0 ) {
printf ("No threads create!");
free (myThread);
exit(-1);
}
}
multiplyThread(0);
for (counter = 1; counter < myNrThreads; ++counter) {
pthread_join(myThread[counter], NULL);
}
for (counter = 0; counter < rowA; ++counter) {
for (j = 0; j < colB; ++j) {
printf ("%.5f ", matrixOut[counter][j]);
}
printf("\n");
}
fclose(fileA);
fclose(fileB);
free(myThread);
free(matrixA);
free(matrixB);
free(matrixOut);
return 0;
}
/*
* The method gets on the first line the dimensions of the matrice.
* While filling every postion of our matrice, we control
* if the given dimensions are the real dimensions of the matrice.
* Everything is read from the .txt file, produced from our python
* generator.
*
*/
void *multiplyThread(void *param){
int myParam = (int)param;
int limitBegin = (myParam * rowA) / myNrThreads;
int limitEnd = ((myParam + 1) * rowA) / myNrThreads;
int counterI, counterJ, counterK;
for (counterI = limitBegin; counterI < rowA; ++counterI) {
for (counterJ = 0; counterJ < colB; ++counterJ) {
matrixOut[counterI][counterJ] = 0;
for (counterK = 0; counterK < rowB; ++counterK) {
matrixOut[counterI][counterJ] +=matrixA[counterI][counterK] * matrixB[counterK][counterJ];
}
}
}
printf("finished slice %d\n", myParam);
return 0;
}
Any idea why???
Thanx in advance.
PS: at the pthread_create I get a warning at (void*)counter btw
EDIT:
matrixA and matrixB are given through matrixA.txt and matrixB.txt. They are read and the values are taken from that.
One of the txt file would look like this:
2 2 // The dimensions of the matrice
12 14
13 15
EDIT3: The new one. Here I get segmentation fault 11:
#include <stdio.h>
#include <pthread.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
void *multiplyThread (void *param);
int rowA, rowB, colA, colB;
int myNrThreads = 0;
double **matrixA, **matrixB, **matrixOut;
void fillAndCheckMatrice(double **matrix, FILE *myFile, int ID) {
char *line = NULL;
char *p;
int row, column;
ssize_t read;
int i = 0, j = 0;
size_t length = 0;
getline (&line, &length, myFile);
p = strtok(line, " ");
row = atoi(p);
p = strtok(NULL, " ");
column = atoi(p);
printf("%d, %d\n", row, column);
if (ID == 1) {
rowA = row;
colA = column;
} else if (ID == 2) {
rowB = row;
colB = column;
}
matrix = malloc(row * sizeof(double*));
for (j = 0; j < row; ++j) {
matrix[j] = malloc(column * sizeof(double));
}
i = 0;
while ((read = getline (&line, &length, myFile)) != -1) {
j = 0;
p = strtok(line, " ");
while (p != NULL) {
matrix[i][j] = atof(p);
++j;
p = strtok(NULL, " ");
}
++i;
}
free(line);
}
int main (int argc, char* argv[])
{
pthread_t *myThread;
int counter, j, r;
FILE *fileA = fopen("matrixA.txt", "r");
FILE *fileB = fopen ("matrixB.txt", "r");
if (argc!=2)
{
printf("Usage: %s number_of_threads\n",argv[0]);
exit(-1);
}
myNrThreads = (atoi)(argv[1]);
fillAndCheckMatrice(matrixA, fileA, 1);
fillAndCheckMatrice(matrixB, fileB, 2);
matrixOut = malloc(rowA * sizeof(double*));
for (counter = 0; counter < rowA; ++counter) {
matrixOut[counter] = malloc (colB * sizeof(double));
}
for (counter = 0; counter < rowA; ++counter) {
for (j = 0; j < colB; ++j) {
printf ("%.5f ", matrixOut[counter][j]);
}
printf("\n");
}
myThread = malloc(myNrThreads * sizeof(pthread_t));
for (counter = 1; counter < myNrThreads; ++counter) {
printf("%d", counter);
if (pthread_create (&myThread[counter], NULL, multiplyThread, (void*)(intptr_t)counter) != 0) {
printf ("No threads create!");
free (myThread);
exit(-1);
}
}
for (counter = 0; counter < rowA; ++counter) {
for (j = 0; j < colB; ++j) {
printf ("%.5f ", matrixA[counter][j]);
}
printf("\n");
}
multiplyThread(0);
for (counter = 1; counter < myNrThreads; ++counter) {
pthread_join(myThread[counter], NULL);
}
fclose(fileA);
fclose(fileB);
free(myThread);
free(matrixA);
free(matrixB);
free(matrixOut);
return 0;
}
/*
* The method gets on the first line the dimensions of the matrice.
* While filling every postion of our matrice, we control
* if the given dimensions are the real dimensions of the matrice.
* Everything is read from the .txt file, produced from our python
* generator.
*
*/
void *multiplyThread(void *param){
int myParam = (int)param;
int limitBegin = (myParam * rowA) / myNrThreads;
int limitEnd = ((myParam + 1) * rowA) / myNrThreads;
int counterI, counterJ, counterK;
for (counterI = limitBegin; counterI < rowA; ++counterI) {
for (counterJ = 0; counterJ < colB; ++counterJ) {
matrixOut[counterI][counterJ] = 0;
for (counterK = 0; counterK < rowB; ++counterK) {
matrixOut[counterI][counterJ] +=matrixA[counterI][counterK] * matrixB[counterK][counterJ];
}
}
}
printf("finished slice %d\n", myParam);
return 0;
}

Answer 1

There are quite a few problems in the question code. Perhaps the best 'answer' would be to carefully walk through the code and point out some of the issues.
First, consider the following:
int rowA, rowB, colA, colB;
Nothing really wrong with the above line, until (later in main):
fillAndCheckMatrice(matrixA, fileA, rowA, colA);
fillAndCheckMatrice(matrixB, fileB, rowB, colB);
The above lines pass the 'values' of 'rowA', 'colA' 'rowB' and 'colB'. Being that these variables have no established values, it is obvious that there is trouble in the code.
Most likely, the intention is to initialize these values inside the 'fillAndCheckMatrice()' function. However, in order to initialize these variables, the 'address' of the variables must be passed into 'fillAndCheckMatrice()', (not their 'values'). Perhaps something like this:
fillAndCheckMatrice(matrixA, fileA, &rowA, &colA);
fillAndCheckMatrice(matrixB, fileB, &rowB, &colB);
Then, of course, the 'fillAndCheckMatrice()' will have to be modified as well; from:
void fillAndCheckMatrice(double **matrix, FILE *myFile, int row, int column) {
To:
void fillAndCheckMatrice(double **matrix, FILE *myFile, int *row, int *column) {
And then, of course, every reference to 'row' and 'column' will now have to deal with a pointer to a variable, instead of the variable value. Hence these:
row = atoi(p);
column = atoi(p);
printf("%d, %d\n", row, column);
Will have to change to these:
*row = atoi(p);
*column = atoi(p);
printf("%d, %d\n", *row, *column);
...and so forth...
matrix = malloc((*row) * sizeof(double*));
for (j = 0; j < *row; ++j) {
I will proceed debugging the question source upon request.