Interleaved Residaul Calculation

Improves Cache Hit Ratio
Signed-off-by: Gaurav Kukreja <mailme.gaurav@gmail.com>

heat-seq/heat.c

@@ -116,11 +116,10 @@ int main( int argc, char *argv[] )
 
 		case 0: // JACOBI
       
-		    relax_jacobi(param.u, param.uhelp, np, np);
+		    residual = relax_jacobi_return_residual(param.u, param.uhelp, np, np);
 			tmp = param.u;
 			param.u = param.uhelp;
 			param.uhelp = tmp;
-		    residual = residual_jacobi( param.u, np, np);
 		    break;
 
 		case 1: // GAUSS

heat-seq/heat.h

@@ -59,7 +59,7 @@ void relax_gauss( double *u,
 // Jacobi: relax_jacobi.c
 double residual_jacobi( double *u,
 			unsigned sizex, unsigned sizey );
-void relax_jacobi( double *u, double *utmp,
+double relax_jacobi_return_residual( double *u, double *utmp,
 		   unsigned sizex, unsigned sizey ); 
 
 

heat-seq/relax_jacobi.c

@@ -38,19 +38,36 @@ double residual_jacobi( double *u,
 /*
  * One Jacobi iteration step
  */
-void relax_jacobi( double *u, double *utmp,
-		   unsigned sizex, unsigned sizey )
+double relax_jacobi_return_residual( double *u, double *utmp,
+		unsigned sizex, unsigned sizey )
 {
-    int i, j;
-  
-    for( i=1; i<sizey-1; i++ )
-    {
-	for( j=1; j<sizex-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
+	int i, j;
+	double unew, diff, sum=0.0;
+
+	for( i=1; i<sizey; i++ )
+	{
+		for( j=1; j<sizex-1; j++ )
+		{
+			if(i<sizey-1)
+			{
+				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
+			}
+
+			//Residual Calculation
+			if(i>1)
+			{
+				unew = 0.25 * (utmp[ (i-1)*sizex+j -1 ]+  // left
+						utmp[ (i-1)*sizex+j +1 ]+  // right
+						utmp[ (i-2)*sizex + j ]+  // top
+						utmp[ (i)*sizex + j ]); // bottom
+
+				diff = unew - utmp[(i-1)*sizex+j];
+				sum += diff * diff;
+			}
+		}
 	}
-    }
+	return sum;
 }