Matrix Multiplication in C programming

Question

Given an n x k matrix A and an k x m matrix B, with 1≤n,m,k≤300, write a C program that computes the matrix product C=AB. All entries in matrices A and B are integers with abolute value less than 1000, so you don't need to worry about overflow.

If matrices A and B do not have the right dimensions to be multiplied, the product matrix C should have its number of rows and columns both set to zero.

Input/Output: please use scanf and printf to handle the data input and output. Input

format:

Line 1: Two space-separated integers, n and k.

Line 2 to n+1: Each line contains k integers separated by sapces: Each row of matrix A.

Line n+2: Two space-separated integers, k and m.

Line n+3 to n+k+4: Each line contains m integers separated by spaces: Each row of matrix B.

Sample Input:

3 2

1 1

1 2

-4 0

2 3

1 2 1

3 2 1

Output format:

Line 1: two space-separated n and m, the dimension of matrix C.

Line 2 to m+1: Each line contains m space-separated integers: Each row of matrix C.

Sample Output:

3 3

4 4 2

7 6 3

-4 -8 -4

please use 2D arrays and do not use a library for auto matrix multiplication.

Answer 1

#include <stdio.h>

#define MAX_MATRIX_DIMENSION (100)

typedef struct _TMatrix

{

int numRows;

int numColumns;

double matrix[MAX_MATRIX_DIMENSION][MAX_MATRIX_DIMENSION];

} * TMatrix;

int Matrix_UserInput(TMatrix matrix)

{

int i,j;

double x;

printf(" Please input the # of rows :>");

scanf("%d",&matrix->numRows);

printf("Please input the # of columns :>");

scanf("%d",&matrix->numColumns);

for (i=0; i<matrix->numRows; i++)

{

for (j=0; j<matrix->numColumns; j++)

{

printf(" Please input the value of the matrix entry row %d and column %d :>",(i+1),(j+1));

scanf("%lf",&x);

matrix->matrix[i][j]=x;

}

}

}

int Matrix_ReadInput(char * filename,TMatrix matrix1, TMatrix matrix2)

{

int iReturn=0;

int rowLoop,columnLoop;

FILE * fptr = fopen(filename,"r");

if (fptr!=NULL)

{

//reads first matrix

fscanf(fptr,"%d %d",&matrix1->numRows,&matrix1->numColumns);

//debug

printf(" dimensions of first matrix: %d %d \n",matrix1->numRows,matrix1->numColumns);

for (rowLoop=0; rowLoop<matrix1->numRows; rowLoop++)

{

for (columnLoop=0; columnLoop<matrix1->numColumns; columnLoop++)

{

fscanf(fptr,"%lf",&matrix1->matrix[rowLoop][columnLoop]);

//debug

printf(" matrix1 : entry at %d %d is %lf \n",rowLoop,columnLoop,matrix1->matrix[rowLoop][columnLoop]);

}

fscanf(fptr,"\n"); //eats the newline

}

//reads second matrix

fscanf(fptr,"%d %d \n",&matrix2->numRows,&matrix2->numColumns);

printf(" dimensions of second matrix: %d %d \n",matrix2->numRows,matrix2->numColumns);

for (rowLoop=0; rowLoop<matrix2->numRows; rowLoop++)

{

for (columnLoop=0; columnLoop<matrix2->numColumns; columnLoop++)

{

fscanf(fptr,"%lf",&matrix2->matrix[rowLoop][columnLoop]);

//debug

printf(" matrix2 : entry at %d %d is %lf \n",rowLoop,columnLoop,matrix2->matrix[rowLoop][columnLoop]);

}

}

fclose(fptr);

}

else

{

iReturn=-1;

}

return(iReturn);

}

Matrix_Multiply(TMatrix matrix1, TMatrix matrix2, TMatrix matrixProduct)

{

int i,j,k;

//Enforces the rule: N by k times k by M = N by M

matrixProduct->numRows=matrix1->numRows;

matrixProduct->numColumns=matrix2->numColumns;

// Multiplying first and second matrices and storing it in result

for (i = 0; i < matrix1->numRows; ++i)

{

for (j = 0; j < matrix2->numColumns; ++j)

{

matrixProduct->matrix[i][j]=0;

for (k = 0; k < matrix1->numColumns; ++k)

{

matrixProduct->matrix[i][j] += matrix1->matrix[i][k] * matrix2->matrix[k][j];

}

printf(" matrix product at %d %d is %lf \n",i,j,matrixProduct->matrix[i][j]);

}

}

}

Matrix_WriteOutput(char * filename, TMatrix m)

{

int i,j;

int iReturn=0;

FILE * fptr = fopen(filename,"w");

if (fptr!=NULL)

{

fprintf(fptr,"%d %d \n",m->numRows,m->numColumns);

for (i=0; i<m->numRows; i++)

{

for (j=0; j<m->numColumns; j++)

{

fprintf(fptr,"%lf ",m->matrix[i][j]);

}

fprintf(fptr,"\n");

}

fclose(fptr);

}

else

{

iReturn=-1;

}

}

Matrix_Display(TMatrix matrix, char * strMessage)

{

int i,j;

if (strMessage!=NULL)

{

printf("*********************************************************\n");

printf(strMessage);

}

printf("****************************************************************\n");

printf(" The dimensions of this matrix is %d rows by %d columns \n\n",matrix->numRows,matrix->numColumns);

for (i=0; i<matrix->numRows; i++)

{

for (j=0; j<matrix->numColumns; j++)

{

printf("%6.0lf ",matrix->matrix[i][j]);

}

printf("\n");

}

}

int main()

{

struct _TMatrix matrix1;

struct _TMatrix matrix2;

struct _TMatrix matrixProduct;

printf("1st Matrix \n ------------------\n");

Matrix_UserInput(&matrix1);

printf("2nd Matrix \n--------------------\n");

Matrix_UserInput(&matrix2);

if (matrix1.numColumns!=matrix2.numRows)

{

//the sizes are incompatible: gripes and complains

printf(" Matrices do not have the proper compatible sizes to be multiplied \n");

printf(" # of columns of 1st matrix MUST EQUAL # of rows of 2nd matrix \n");

printf(" Formula is: N by k times k by M \n");

}

else

{

Matrix_Multiply(&matrix1,&matrix2,&matrixProduct);

//Matrix_WriteOutput((char*)"E:\\matrix_output.dat",&matrixProduct);

Matrix_Display(&matrixProduct,(char*)"The Product Matrix");

}

}