Loop Blocking

To improve Cache Hit Ratio for larger resolutions
Signed-off-by: Gaurav Kukreja <mailme.gaurav@gmail.com>

heat-seq/heat.c

@@ -12,6 +12,7 @@
 #include "heat.h"
 #include "timing.h"
 
+#define BLOCKSIZE 100
 
 void usage( char *s )
 {
@@ -26,6 +27,8 @@ int main( int argc, char *argv[] )
     FILE *infile, *resfile;
     char *resfilename;
 
+	unsigned BlockSize = BLOCKSIZE;
+
 	double *tmp;
 
     // algorithmic parameters
@@ -116,7 +119,7 @@ int main( int argc, char *argv[] )
 
 		case 0: // JACOBI
       
-		    residual = relax_jacobi_return_residual(param.u, param.uhelp, np, np);
+		    residual = relax_jacobi_return_residual(param.u, param.uhelp, np, np, BlockSize);
 			tmp = param.u;
 			param.u = param.uhelp;
 			param.uhelp = tmp;

heat-seq/heat.h

@@ -62,7 +62,7 @@ double residual_jacobi( double *u,
 			unsigned sizex, unsigned sizey );
 #endif
 double relax_jacobi_return_residual( double *u, double *utmp,
-		   unsigned sizex, unsigned sizey ); 
+		   unsigned sizex, unsigned sizey, unsigned BlockSize ); 
 
 
 #endif // JACOBI_H_INCLUDED

heat-seq/relax_jacobi.c

@@ -40,25 +40,28 @@ double residual_jacobi( double *u,
  * One Jacobi iteration step
  */
 double relax_jacobi_return_residual( double *u, double *utmp,
-		unsigned sizex, unsigned sizey )
+		unsigned sizex, unsigned sizey, unsigned BlockSize )
 {
-	int i, j;
+	int i, j, k, l;
 	double unew, diff, sum=0.0;
 
-	for( i=1; i<sizey-1; i++ )
-	{
-		for( j=1; j<sizex-1; j++ )
+	unsigned BlockCountX = (sizex-2)/BlockSize;
+	unsigned BlockCountY = (sizey-2)/BlockSize;
+
+	for ( k = 0; k < BlockCountY; k++)
+		for ( l = 0; l < BlockCountX; l++)
 		{
-			{
-				utmp[i*sizex + j]= 0.25 * (u[ i*sizex+j -1 ]+  // left
-						u[ i*sizex+j +1 ]+  // right
-						u[ (i-1)*sizex + j ]+  // top
-						u[ (i+1)*sizex + j ]); // bottom
+			for( i=1 + BlockSize*k; i <= BlockSize*(k+1); i++ )
+				for( j=1 + BlockSize*l; j <= BlockSize*(l+1); j++ )
+				{
+					utmp[i*sizex+j]= 0.25 * (u[ i*sizex     + (j-1) ]+  // left
+							u[ i*sizex     + (j+1) ]+  // right
+							u[ (i-1)*sizex + j     ]+  // top
+							u[ (i+1)*sizex + j     ]); // bottom
 
-				diff = utmp[i*sizex + j] - u[i*sizex +j];
-				sum += diff * diff;
-			}
+					diff = utmp[i*sizex + j] - u[i*sizex +j];
+					sum += diff * diff;
+				}
 		}
-	}
 	return sum;
 }