Split the microkernel workload into chunks of 32 floats for dsdot mode to limit loss of precision

kernel/x86_64/sdot.c

@@ -78,7 +78,12 @@ FLOAT CNAME(BLASLONG n, FLOAT *x, BLASLONG inc_x, FLOAT *y, BLASLONG inc_y)
 	BLASLONG ix=0,iy=0;
 	double dot = 0.0 ;
 
+#if defined (DSDOT)
+        double mydot = 0.0;
+        FLOAT asmdot = 0.0;
+#else
 	FLOAT mydot=0.0;
+#endif
 	BLASLONG n1;
 
 	if ( n <= 0 )  return(dot);
@@ -89,9 +94,23 @@ FLOAT CNAME(BLASLONG n, FLOAT *x, BLASLONG inc_x, FLOAT *y, BLASLONG inc_y)
 	        n1 = n & (BLASLONG)(-32);
 
 		if ( n1 )
+#if defined(DSDOT)
+			{
+			FLOAT *x1=x;
+			FLOAT *y1=y;
+			BLASLONG n2 = 32;
+			while (i<n1) {
+				sdot_kernel_16(n2, x1, y1 , &asmdot );
+				mydot += (double)asmdot;
+				asmdot=0.;
+				x1+=32;
+				y1+=32;
+				i+=32;
+			}
+		}
+#else		
 			sdot_kernel_16(n1, x, y , &mydot );
-
-
+#endif
 		i = n1;
 		while(i < n)
 		{
@@ -103,11 +122,8 @@ FLOAT CNAME(BLASLONG n, FLOAT *x, BLASLONG inc_x, FLOAT *y, BLASLONG inc_y)
 			i++ ;
 
 		}
-#if defined(DSDOT)
-                dot+=(double)mydot;
-#else                
+
 		dot+=mydot;
-#endif
 		return(dot);