fix: update implementation to preserve signed zeros

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---

Author: kgryte

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

@@ -45,20 +45,34 @@ var isnan = require( '@stdlib/math/base/assert/is-nan' );
 function dsnansumors( N, x, strideX, offsetX ) {
 	var sum;
 	var ix;
+	var v;
 	var i;
 
-	sum = 0.0;
 	if ( N <= 0 ) {
-		return sum;
+		return 0.0;
 	}
 	ix = offsetX;
 	if ( strideX === 0 ) {
 		if ( isnan( x[ ix ] ) ) {
-			return sum;
+			return 0.0;
 		}
 		return N * x[ ix ];
 	}
+	// Find the first non-NaN element...
 	for ( i = 0; i < N; i++ ) {
+		v = x[ ix ];
+		if ( isnan( v ) === false ) {
+			break;
+		}
+		ix += strideX;
+	}
+	if ( i === N ) {
+		return 0.0;
+	}
+	sum = v;
+	ix += strideX;
+	i += 1;
+	for ( ; i < N; i++ ) {
 		if ( isnan( x[ ix ] ) === false ) {
 			sum += x[ ix ];
 		}

lib/node_modules/@stdlib/blas/ext/base/dsnansumors/src/main.c

@@ -47,19 +47,33 @@ double API_SUFFIX(stdlib_strided_dsnansumors_ndarray)( const CBLAS_INT N, const
 	CBLAS_INT ix;
 	CBLAS_INT i;
 	double sum;
+	double v;
 
-	sum = 0.0;
 	if ( N <= 0 ) {
-		return sum;
+		return 0.0;
 	}
 	ix = offsetX;
 	if ( strideX == 0 ) {
 		if ( stdlib_base_is_nanf( X[ ix ] ) ) {
-			return sum;
+			return 0.0;
 		}
 		return N * X[ ix ];
 	}
+	// Find the first non-NaN element...
 	for ( i = 0; i < N; i++ ) {
+		v = X[ ix ];
+		if ( !stdlib_base_is_nanf( v ) ) {
+			break;
+		}
+		ix += strideX;
+	}
+	if ( i == N ) {
+		return 0.0;
+	}
+	sum = (double)v;
+	ix += strideX;
+	i += 1;
+	for ( ; i < N; i++ ) {
 		if ( !stdlib_base_is_nanf( X[ ix ] ) ) {
 			sum += (double)X[ ix ];
 		}

lib/node_modules/@stdlib/blas/ext/base/dsnansumors/test/test.ndarray.js

@@ -21,6 +21,7 @@
 // MODULES //
 
 var tape = require( 'tape' );
+var isNegativeZero = require( '@stdlib/math/base/assert/is-negative-zero' );
 var Float32Array = require( '@stdlib/array/float32' );
 var dsnansumors = require( './../lib/ndarray.js' );
 
@@ -77,6 +78,17 @@ tape( 'the function calculates the sum of strided array elements (ignoring NaN v
 	t.end();
 });
 
+tape( 'the function preserves the sign of zero', function test( t ) {
+	var x;
+	var v;
+
+	x = new Float32Array( [ -0.0, -0.0, -0.0, -0.0, -0.0 ] );
+	v = dsnansumors( x.length, x, 1, 0 );
+	t.strictEqual( isNegativeZero( v ), true, 'returns expected value' );
+
+	t.end();
+});
+
 tape( 'if provided an `N` parameter less than or equal to `0`, the function returns `0.0`', function test( t ) {
 	var x;
 	var v;

lib/node_modules/@stdlib/blas/ext/base/dsnansumors/test/test.ndarray.native.js

@@ -22,6 +22,7 @@
 
 var resolve = require( 'path' ).resolve;
 var tape = require( 'tape' );
+var isNegativeZero = require( '@stdlib/math/base/assert/is-negative-zero' );
 var Float32Array = require( '@stdlib/array/float32' );
 var tryRequire = require( '@stdlib/utils/try-require' );
 
@@ -86,6 +87,17 @@ tape( 'the function calculates the sum of strided array elements (ignoring NaN v
 	t.end();
 });
 
+tape( 'the function preserves the sign of zero', opts, function test( t ) {
+	var x;
+	var v;
+
+	x = new Float32Array( [ -0.0, -0.0, -0.0, -0.0, -0.0 ] );
+	v = dsnansumors( x.length, x, 1, 0 );
+	t.strictEqual( isNegativeZero( v ), true, 'returns expected value' );
+
+	t.end();
+});
+
 tape( 'if provided an `N` parameter less than or equal to `0`, the function returns `0.0`', opts, function test( t ) {
 	var x;
 	var v;