fix: update implementation to preserve signed zeros

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---

Author: kgryte

lib/node_modules/@stdlib/blas/ext/base/gsumpw/lib/accessors.js

@@ -89,8 +89,9 @@ function gsumpw( N, x, strideX, offsetX ) {
 	}
 
 	if ( N <= 8 ) {
-		s = 0.0;
-		for ( i = 0; i < N; i++ ) {
+		s = get( xbuf, ix );
+		ix += strideX;
+		for ( i = 1; i < N; i++ ) {
 			s += get( xbuf, ix );
 			ix += strideX;
 		}

lib/node_modules/@stdlib/blas/ext/base/gsumpw/lib/ndarray.js

@@ -85,8 +85,9 @@ function gsumpw( N, x, strideX, offsetX ) {
 	}
 	if ( N < 8 ) {
 		// Use simple summation...
-		s = 0.0;
-		for ( i = 0; i < N; i++ ) {
+		s = x[ ix ];
+		ix += strideX;
+		for ( i = 1; i < N; i++ ) {
 			s += x[ ix ];
 			ix += strideX;
 		}