feat: add support for accessor arrays in blas/ext/base/gsumpw

PR-URL: #4859
Co-authored-by: Athan Reines <[email protected]>
Reviewed-by: Athan Reines <[email protected]>

lib/node_modules/@stdlib/blas/ext/base/gsumpw/README.md

@@ -110,6 +110,7 @@ var v = gsumpw.ndarray( 4, x, 2, 1 );
 
 -   If `N <= 0`, both functions return `0.0`.
 -   In general, pairwise summation is more numerically stable than ordinary recursive summation (i.e., "simple" summation), with slightly worse performance. While not the most numerically stable summation technique (e.g., compensated summation techniques such as the Kahan–Babuška-Neumaier algorithm are generally more numerically stable), pairwise summation strikes a reasonable balance between numerical stability and performance. If either numerical stability or performance is more desirable for your use case, consider alternative summation techniques.
+-   Both functions support array-like objects having getter and setter accessors for array element access (e.g., [`@stdlib/array/base/accessor`][@stdlib/array/base/accessor]).
 -   Depending on the environment, the typed versions ([`dsumpw`][@stdlib/blas/ext/base/dsumpw], [`ssumpw`][@stdlib/blas/ext/base/ssumpw], etc.) are likely to be significantly more performant.
 
 </section>
@@ -178,6 +179,8 @@ console.log( v );
 
 [mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
 
+[@stdlib/array/base/accessor]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/base/accessor
+
 [@higham:1993a]: https://doi.org/10.1137/0914050
 
 <!-- <related-links> -->

lib/node_modules/@stdlib/blas/ext/base/gsumpw/docs/types/index.d.ts

@@ -20,7 +20,12 @@
 
 /// <reference types="@stdlib/types"/>
 
-import { NumericArray } from '@stdlib/types/array';
+import { NumericArray, Collection, AccessorArrayLike } from '@stdlib/types/array';
+
+/**
+* Input array.
+*/
+type InputArray = NumericArray | Collection<number> | AccessorArrayLike<number>;
 
 /**
 * Interface describing `gsumpw`.
@@ -40,7 +45,7 @@ interface Routine {
 	* var v = gsumpw( x.length, x, 1 );
 	* // returns 1.0
 	*/
-	( N: number, x: NumericArray, strideX: number ): number;
+	( N: number, x: InputArray, strideX: number ): number;
 
 	/**
 	* Computes the sum of strided array elements using pairwise summation and alternative indexing semantics.
@@ -57,7 +62,7 @@ interface Routine {
 	* var v = gsumpw.ndarray( x.length, x, 1, 0 );
 	* // returns 1.0
 	*/
-	ndarray( N: number, x: NumericArray, strideX: number, offsetX: number ): number;
+	ndarray( N: number, x: InputArray, strideX: number, offsetX: number ): number;
 }
 
 /**

lib/node_modules/@stdlib/blas/ext/base/gsumpw/docs/types/test.ts

@@ -16,6 +16,7 @@
 * limitations under the License.
 */
 
+import AccessorArray = require( '@stdlib/array/base/accessor' );
 import gsumpw = require( './index' );
 
 
@@ -26,6 +27,7 @@ import gsumpw = require( './index' );
 	const x = new Float64Array( 10 );
 
 	gsumpw( x.length, x, 1 ); // $ExpectType number
+	gsumpw( x.length, new AccessorArray( x ), 1 ); // $ExpectType number
 }
 
 // The compiler throws an error if the function is provided a first argument which is not a number...
@@ -85,6 +87,7 @@ import gsumpw = require( './index' );
 	const x = new Float64Array( 10 );
 
 	gsumpw.ndarray( x.length, x, 1, 0 ); // $ExpectType number
+	gsumpw.ndarray( x.length, new AccessorArray( x ), 1, 0 ); // $ExpectType number
 }
 
 // The compiler throws an error if the `ndarray` method is provided a first argument which is not a number...

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

@@ -0,0 +1,146 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2025 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+// MODULES //
+
+var floor = require( '@stdlib/math/base/special/floor' );
+
+
+// VARIABLES //
+
+// Blocksize for pairwise summation (NOTE: decreasing the blocksize decreases rounding error as more pairs are summed, but also decreases performance. Because the inner loop is unrolled eight times, the blocksize is effectively `16`.):
+var BLOCKSIZE = 128;
+
+
+// MAIN //
+
+/**
+* Computes the sum of strided array elements using pairwise summation.
+*
+* ## Method
+*
+* -   This implementation uses pairwise summation, which accrues rounding error `O(log2 N)` instead of `O(N)`. The recursion depth is also `O(log2 N)`.
+*
+* ## References
+*
+* -   Higham, Nicholas J. 1993. "The Accuracy of Floating Point Summation." _SIAM Journal on Scientific Computing_ 14 (4): 783–99. doi:[10.1137/0914050](https://doi.org/10.1137/0914050).
+*
+* @private
+* @param {PositiveInteger} N - number of indexed elements
+* @param {Object} x - input array object
+* @param {Collection} x.data - input array data
+* @param {Array<Function>} x.accessors - array element accessors
+* @param {integer} strideX - stride length
+* @param {NonNegativeInteger} offsetX - starting index
+* @returns {number} sum
+*
+* @example
+* var toAccessorArray = require( '@stdlib/array/base/to-accessor-array' );
+* var arraylike2object = require( '@stdlib/array/base/arraylike2object' );
+*
+* var x = toAccessorArray( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
+*
+* var v = gsumpw( 4, arraylike2object( x ), 2, 1 );
+* // returns 5.0
+*/
+function gsumpw( N, x, strideX, offsetX ) {
+	var xbuf;
+	var get;
+	var ix;
+	var s0;
+	var s1;
+	var s2;
+	var s3;
+	var s4;
+	var s5;
+	var s6;
+	var s7;
+	var M;
+	var n;
+	var s;
+	var i;
+
+	if ( N <= 0 ) {
+		return 0.0;
+	}
+
+	// Cache reference to array data:
+	xbuf = x.data;
+
+	// Cache a reference to the element accessor:
+	get = x.accessors[ 0 ];
+
+	ix = offsetX;
+	if ( strideX === 0 ) {
+		return N * get( xbuf, ix );
+	}
+
+	if ( N <= 8 ) {
+		s = 0.0;
+		for ( i = 0; i < N; i++ ) {
+			s += get( xbuf, ix );
+			ix += strideX;
+		}
+		return s;
+	}
+	if ( N <= BLOCKSIZE ) {
+		// Sum a block with 8 accumulators (by loop unrolling, we lower the effective blocksize to 16)...
+		s0 = get( xbuf, ix );
+		s1 = get( xbuf, ix+strideX );
+		s2 = get( xbuf, ix+(2*strideX) );
+		s3 = get( xbuf, ix+(3*strideX) );
+		s4 = get( xbuf, ix+(4*strideX) );
+		s5 = get( xbuf, ix+(5*strideX) );
+		s6 = get( xbuf, ix+(6*strideX) );
+		s7 = get( xbuf, ix+(7*strideX) );
+		ix += 8 * strideX;
+
+		M = N % 8;
+		for ( i = 8; i < N-M; i += 8 ) {
+			s0 += get( xbuf, ix );
+			s1 += get( xbuf, ix+strideX );
+			s2 += get( xbuf, ix+(2*strideX) );
+			s3 += get( xbuf, ix+(3*strideX) );
+			s4 += get( xbuf, ix+(4*strideX) );
+			s5 += get( xbuf, ix+(5*strideX) );
+			s6 += get( xbuf, ix+(6*strideX) );
+			s7 += get( xbuf, ix+(7*strideX) );
+			ix += 8 * strideX;
+		}
+		// Pairwise sum the accumulators:
+		s = ( (s0+s1) + (s2+s3) ) + ( (s4+s5) + (s6+s7) );
+
+		// Clean-up loop...
+		for ( i; i < N; i++ ) {
+			s += get( xbuf, ix );
+			ix += strideX;
+		}
+		return s;
+	}
+	// Recurse by dividing by two, but avoiding non-multiples of unroll factor...
+	n = floor( N/2 );
+	n -= n % 8;
+	return gsumpw( n, x, strideX, ix ) + gsumpw( N-n, x, strideX, ix+(n*strideX) ); // eslint-disable-line max-len
+}
+
+
+// EXPORTS //
+
+module.exports = gsumpw;

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

@@ -21,6 +21,8 @@
 // MODULES //
 
 var floor = require( '@stdlib/math/base/special/floor' );
+var arraylike2object = require( '@stdlib/array/base/arraylike2object' );
+var accessors = require( './accessors.js' );
 
 
 // VARIABLES //
@@ -66,12 +68,17 @@ function gsumpw( N, x, strideX, offsetX ) {
 	var s7;
 	var M;
 	var s;
+	var o;
 	var n;
 	var i;
 
 	if ( N <= 0 ) {
 		return 0.0;
 	}
+	o = arraylike2object( x );
+	if ( o.accessorProtocol ) {
+		return accessors( N, o, strideX, offsetX );
+	}
 	ix = offsetX;
 	if ( strideX === 0 ) {
 		return N * x[ ix ];

lib/node_modules/@stdlib/blas/ext/base/gsumpw/test/test.main.js

@@ -23,6 +23,7 @@
 var tape = require( 'tape' );
 var isnan = require( '@stdlib/math/base/assert/is-nan' );
 var Float64Array = require( '@stdlib/array/float64' );
+var toAccessorArray = require( '@stdlib/array/base/to-accessor-array' );
 var gsumpw = require( './../lib' );
 
 
@@ -74,6 +75,33 @@ tape( 'the function calculates the sum of all strided array elements', function
 	t.end();
 });
 
+tape( 'the function calculates the sum of all strided array elements (accessors)', function test( t ) {
+	var x;
+	var v;
+
+	x = [ 1.0, -2.0, -4.0, 5.0, 0.0, 3.0, 0.0, -3.0, 3.0 ];
+	v = gsumpw( x.length, toAccessorArray( x ), 1 );
+	t.strictEqual( v, 3.0, 'returns expected value' );
+
+	x = [ 1.0, -2.0, -4.0, 5.0, 0.0, 3.0 ];
+	v = gsumpw( x.length, toAccessorArray( x ), 1 );
+	t.strictEqual( v, 3.0, 'returns expected value' );
+
+	x = [ -4.0, -4.0 ];
+	v = gsumpw( x.length, toAccessorArray( x ), 1 );
+	t.strictEqual( v, -8.0, 'returns expected value' );
+
+	x = [ NaN, 4.0 ];
+	v = gsumpw( x.length, toAccessorArray( x ), 1 );
+	t.strictEqual( isnan( v ), true, 'returns expected value' );
+
+	x = [ 1.0, 1.0e100, 1.0, -1.0e100 ];
+	v = gsumpw( x.length, toAccessorArray( x ), 1 );
+	t.strictEqual( v, 0.0, '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;
@@ -122,6 +150,27 @@ tape( 'the function supports a `stride` parameter', function test( t ) {
 	t.end();
 });
 
+tape( 'the function supports a `stride` parameter (accessors)', function test( t ) {
+	var x;
+	var v;
+
+	x = [
+		1.0,  // 0
+		2.0,
+		2.0,  // 1
+		-7.0,
+		-2.0, // 2
+		3.0,
+		4.0,  // 3
+		2.0
+	];
+
+	v = gsumpw( 4, toAccessorArray( x ), 2 );
+
+	t.strictEqual( v, 5.0, 'returns expected value' );
+	t.end();
+});
+
 tape( 'the function supports a negative `stride` parameter', function test( t ) {
 	var x;
 	var v;
@@ -143,6 +192,27 @@ tape( 'the function supports a negative `stride` parameter', function test( t )
 	t.end();
 });
 
+tape( 'the function supports a negative `stride` parameter (accessors)', function test( t ) {
+	var x;
+	var v;
+
+	x = [
+		1.0,  // 3
+		2.0,
+		2.0,  // 2
+		-7.0,
+		-2.0, // 1
+		3.0,
+		4.0,  // 0
+		2.0
+	];
+
+	v = gsumpw( 4, toAccessorArray( x ), -2 );
+
+	t.strictEqual( v, 5.0, 'returns expected value' );
+	t.end();
+});
+
 tape( 'if provided a `stride` parameter equal to `0`, the function returns the sum of the first element repeated N times', function test( t ) {
 	var x;
 	var v;