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/*
* Task 2 - Kronecker Product
*
* GUEST LANGUAGE: THIS IS THE C VERSION OF ch-2.pl.
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <stdint.h>
#include <string.h>
#include <assert.h>
#include <unistd.h>
#include <ctype.h>
bool debug=false;
#define MAXROWS 20
#define MAXCOLS 20
typedef int matrix[MAXROWS][MAXCOLS];
// process_flag_noarg( argc, argv );
// Process the -d flag, and check that there are no
// remaining arguments.
void process_flag_noarg( int argc, char **argv )
{
int arg=1;
if( argc>1 && strcmp( argv[arg], "-d" ) == 0 )
{
debug = true;
arg++;
}
int left = argc-arg;
if( left != 0 )
{
fprintf( stderr,
"Usage: kronecker-product [-d]\n" );
exit(1);
}
}
//
// mat_show( m, rows, cols );
// Show matrix m
//
void mat_show( matrix m, int rows, int cols )
{
// first, calculate the max cell width
int width = 1;
for( int i=0; i<rows; i++ )
{
for( int j=0; j<cols; j++ )
{
char buf[128];
sprintf( buf, "%d", m[i][j] );
int len = strlen(buf);
if( len > width )
{
width = len;
}
}
}
#if 0
fprintf( stderr, "width=%d\n", width );
exit(1);
#endif
for( int i=0; i<rows; i++ )
{
fputs( "[ ", stdout );
for( int j=0; j<cols; j++ )
{
printf( "%*d ", width, m[i][j] );
}
putchar( ']' );
putchar( '\n' );
}
}
//
// kronecker_product( a, ar, ac, b, br, bc, c, &rows, &cols );
// Form the Kronecker product of two matrices A (ar rows x ac cols)
// and B (br rows x bc cols) in C (and setting rows and cols
// to the dimensions of C).
// using the formula (A x B)i,j = Ai/p,j/q * Bi%p,j%q
// [where B is of size p x q]
//
void kronecker_product( matrix a, int m, int n, matrix b, int p, int q, matrix c, int *rp, int *cp )
{
int rows = m * p;
int cols = n * q;
//fprintf( stderr, "rows=%d, cols=%d\n", rows, cols );
for( int i=0; i<rows; i++ )
{
int arow = i / p;
int brow = i % p;
for( int j=0; j<cols; j++ )
{
int acol = j / q;
int bcol = j % q;
c[i][j] = a[arow][acol] * b[brow][bcol];
}
}
*rp = rows;
*cp = cols;
}
void small( void )
{
matrix a = { {1,2}, {3,4} };
//mat_show( a, 2, 2 );
matrix b = { {5, 6}, {7, 8} };
//mat_show( b, 2, 2 );
puts( "[ 1, 2 ] [5, 6]" );
puts( "[ 3, 4 ] k* [7, 8]" );
puts( "is:" );
matrix c;
int rows, cols;
kronecker_product( a, 2, 2, b, 2, 2, c, &rows, &cols );
mat_show( c, rows, cols );
}
void big( void )
{
matrix a = { {1,-4,7}, {-2,3,3} };
//mat_show( a, 2, 3 );
matrix b = {
{8, -9, -6, 5},
{1, -3, -4, 7},
{2, 8, -8, -3},
{1, 2, -5, -1},
};
//mat_show( b, 4, 4 );
puts( "[ 1, -4, 7 ] [8, -9, -6, 5]" );
puts( "[ -2, 3, 3 ] [1, -3, -4, 7]" );
puts( " k* [2, 8, -8, -3]" );
puts( " [1, 2, -5, -1]" );
puts( "is:" );
matrix c;
int cr, cc;
kronecker_product( a, 2, 3, b, 4, 4, c, &cr, &cc );
mat_show( c, cr, cc );
}
int main( int argc, char **argv )
{
process_flag_noarg( argc, argv );
small();
putchar( '\n' );
big();
return 0;
}
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