How do you do matrix multiplication in c using structure?

Answer 1

You took an example of The Product AB is determined as the dot products of the ith row in A and the jth column in B,placed in ith row and jth column of the resulting m x p matrix C.

so: this may help you.

#include <stdio.h>

#include <stdlib.h>

// function prototypes

void Matrix_Mult( int a1[][3], int a2[][4], int a3[][4] );

void Matrix_MultAlt( int a1[][3], int a2[][4], int a3[][4] );

int dot3(const int a1[][3], const int a2[][4], int row, int col);

void PrnNx4 (int ar[][4], int n);

//---------------------------------------------------------------------------------

// Function: main(void)

// Description:

// demonstration of Matrix Multiplication

//

// Programmer: Paul Bladek

//

// Date: 10/31/2001

//

// Version: 1.0

//

// Environment: Hardware:IBM Pentium 4

// Software: Microsoft XP with .NET framework for execution;

// Compiles under Microsoft Visual C++.Net 2005

//

// Calls: Matrix_Mult(int a1[][3], int a2[][4], int a3[][4])

// Matrix_MultAlt(int a1[][3], int a2[][4], int a3[][4])

// PrnNx4(int ar[][4]

//

//

// Parameters: int a1[][3] -- left matrix

// int a2[][4] -- right matrix

// int a3[][4] -- answer matrix

//

// Returns: EXIT_SUCCESS

// ------------------------------------------------------------------------------

int main(void)

{

int A[2][3] = {{1, 3, 4},

{2, 0, 1}},

B[3][4] = {{1, 2, 3, 1},

{2, 2, 2, 2},

{3, 2, 1, 4}},

C[2][4] = {{0, 0, 0, 0},

{0, 0, 0, 0}};

Matrix_Mult(A, B, C);

PrnNx4(C, 2);

Matrix_MultAlt(A, B, C); // alternate form that calls dot3

PrnNx4(C, 2);

return EXIT_SUCCESS;

}

//---------------------------------------------------------------------------------

// Function: Matrix_Mult(int a1[][3], int a2[][4], int a3[][4])

// Description:

// multiplies a 2X3 matrix by a 3X4 matrix

//

// Programmer: Paul Bladek

//

// Date: 10/31/2001

//

// Version: 1.0

//

// Environment: Hardware:IBM Pentium 4

// Software: Microsoft XP with .NET framework for execution;

// Compiles under Microsoft Visual C++.Net 2005

//

// Calls: None

//

// Called By: main()

//

// Parameters: int a1[][3] -- left matrix

// int a2[][3] -- right matrix

// int a3[][3] -- answer matrix

// ------------------------------------------------------------------------------

void Matrix_Mult(int a1[][3], int a2[][4], int a3[][4])

{

int i = 0;

int j = 0;

int k = 0;

for(i = 0; i < 2; i++)

for( j = 0; j < 4; j++)

for( k = 0; k < 3; k++)

a3[i][j] += a1[i][k] * a2[k][j];

}

//---------------------------------------------------------------------------------

// Function: Matrix_MultAlt(int a1[][3], int a2[][4], int a3[][4])

// Description:

// multiplies a 2X3 matrix by a 3X4 matrix -- Alternate Form

//

// Programmer: Paul Bladek

//

// Date: 10/31/2001

//

// Version: 1.0

//

// Environment: Hardware:IBM Pentium 4

// Software: Microsoft XP with .NET framework for execution;

// Compiles under Microsoft Visual C++.Net 2005

//

// Calls: dot3(const int a1[][3], const int a2[][4], int row, int col)

//

// Called By: main()

//

// Parameters: int a1[][3] -- left matrix

// int a2[][3] -- right matrix

// int a3[][3] -- answer matrix

// ------------------------------------------------------------------------------

void Matrix_MultAlt(int a1[][3], int a2[][4], int a3[][4])

{

int i = 0;

int j = 0;

for( i = 0; i < 2; i++)

for( j = 0; j < 4; j++)

a3[i][j] = dot3(a1, a2, i, j);

}

//---------------------------------------------------------------------------------

// Function: dot3(const int a1[][3], const int a2[][4], int row, int col)

// Description:

// dot product of a1 row and a2 col

//

// Programmer: Paul Bladek

//

// Date: 10/31/2001

//

// Version: 1.0

//

// Environment: Hardware:IBM Pentium 4

// Software: Microsoft XP with .NET framework for execution;

// Compiles under Microsoft Visual C++.Net 2005

//

// Calls: None

//

// Called By: Matrix_MultAlt(int a1[][3], int a2[][4], int a3[][4])

//

// Parameters: int a1[][3] -- left matrix

// int a2[][3] -- right matrix

// int row -- the row number

// int col -- the column number

//

// Returns: the dot product

// ------------------------------------------------------------------------------

int dot3(const int a1[][3], const int a2[][4], int row, int col)

{

int k = 0;

int sum = 0;

for( k = 0; k < 3; k++)

sum += a1[row][k] * a2[k][col];

return sum;

}

//---------------------------------------------------------------------------------

// Function: PrnNx4(int ar[][4], int n)

// Description:

// prints out an NX4 matrix

//

// Programmer: Paul Bladek

//

// Date: 10/31/2001

//

// Version: 1.0

//

// Environment: Hardware:IBM Pentium 4

// Software: Microsoft XP with .NET framework for execution;

// Compiles under Microsoft Visual C++.Net 2005

//

// Called By: main()

//

// Parameters: int ar[][4] -- matrix to print

// int n -- number of elements

// ------------------------------------------------------------------------------

void PrnNx4 (int ar[][4], int n)

{

int i = 0;

int j = 0;

for(i = 0; i < n; i++)

{

for( j = 0; j < 4; j++)

printf("%4d", ar[i][j]);

putchar('\n');

}

}