C programming transpose matrix, #define

Question

Can you help me, I have a problem. This is program that transpose matrix. When is number of rows or columns equals 357 or bigger program doesn't work (define MAX_n 357, define MAX_m 357). When is less than 357 program works normally.

#include <stdio.h>
#include <stdlib.h>
#define MAX_m 357
#define MAX_n 357
void main()  
{  
  int a[MAX_m][MAX_n],b[MAX_m][MAX_n]; 
  int r=0,j,i;
  printf("\nProgram to transpose matrix\n");  
  for(i=0;i<MAX_m;i++)  
    {  
        for(j=0;j<MAX_n;j++)  
    {  
      r=rand();
      a[i][j]=r;  
    }  
 }  
 printf("\nMatrix A: "); 
 for(i=0;i<MAX_m;i++)  
 {  
     printf("\n");  
     for(j=0;j<MAX_n;j++)  
    {  
      printf(" ");  
      printf("%d",a[i][j]); 
    }  
 }
 for(i=0;i<MAX_m;i++)  
 {  
    for(j=0;j<MAX_n;j++)  
   {  
     b[i][j]=a[j][i];
   }  
 }  
printf("\nResultant Matrix: "); 
for(i=0;i<MAX_m;i++) 
{  
  printf("\n"); 
  for(j=0;j<MAX_n;j++)
    { 
      printf(" ");  
      printf("%d",b[i][j]);
    }  
    } 
   printf("\n"); 
   return(0);
   }  

Answer 1

As others have stated in comments, this has to be a memory allocation problem. On Unix, you can check ulimit -s in the Bash shell for your stack size limit, or limit stack in tcsh.

Since this looks like homework, I'll leave it to you and your teacher for a discussion on different memory allocation strategies.

PS, it would be helpful in the future to indicate what type of failure you're experiencing, as opposed to just "it didn't work".

Answer 2

I did it in C++, I created a class Matrix. You could easily make it in C from this. I know two-dimensional arrays seem easier to understand (when transposing) but they are simply a convenient way to write them down (with a little overhead) and are equivalent. You can also see how efficient this code is.

#include <iostream>
#include <time.h>
using namespace std;

void print_array(int * A, int rows, int cols);

class Matrix{
int rows, cols;
int *A;

public:
Matrix(){};
Matrix (int *A, int rows, int cols): rows(rows), cols(cols) {
    this->A = A;
    };

Matrix transpose(){
    int* T;
    T = new int[rows*cols];
    int rows_T(this->cols);
    int cols_T(this->rows);
    for(int i=0;i<rows_T;++i){
        for (int j=0;j<cols_T;++j){
            T[i*cols_T+j] = this->A[j*cols+i];  //T[i][j]=A[j][i]
        }
    }   
return Matrix(T, rows_T, cols_T);
};

void print(){
    for (int i=0;i<rows;++i){
        for(int j=0;j<cols;j++){
            cout<<A[i*cols+j]<<" ";
        }
        cout<<" "<<endl;
    }
}
};

void print_array(int * A, int rows, int cols){

for (int i=0;i<rows;++i){
    for(int j=0;j<cols;j++){
        cout<<A[i*cols+j]<<" ";
    }
    cout<<" "<<endl;
}

}



int main(){

clock_t t;
t= clock();

int rows(2000), cols(1000);
int *A = new int[rows*cols];
for(int i=0;i<rows*cols;++i){
    A[i]= rand() %10;
}

Matrix M1(A, rows, cols);

Matrix B;
B = M1.transpose();

t = (clock()-t);
cout<<"took (seconds): "<<t/1000000.0 <<endl;

return 0;
}