feat: add accessor array support to blas/base/gnrm2

PR-URL: #5778
Closes: stdlib-js/metr-issue-tracker#26
Co-authored-by: Athan Reines <[email protected]>
Reviewed-by: Athan Reines <[email protected]> 
Signed-off-by: Athan Reines <[email protected]>

Author: headlessNode

lib/node_modules/@stdlib/blas/base/gnrm2/README.md

@@ -49,7 +49,7 @@ var gnrm2 = require( '@stdlib/blas/base/gnrm2' );
 
 #### gnrm2( N, x, stride )
 
-Computes the [L2-norm][l2-norm] of a vector `x`.
+Computes the [L2-norm][l2-norm] of a vector.
 
 ```javascript
 var x = [ 1.0, -2.0, 2.0 ];
@@ -62,9 +62,9 @@ The function has the following parameters:
 
 -   **N**: number of indexed elements.
 -   **x**: input [`Array`][mdn-array] or [`typed array`][mdn-typed-array].
--   **stride**: index increment for `x`.
+-   **stride**: stride length.
 
-The `N` and `stride` parameters determine which elements in `x` are accessed at runtime. For example, to compute the [L2-norm][l2-norm] of every other element in `x`,
+The `N` and stride parameters determine which elements in the strided array are accessed at runtime. For example, to compute the [L2-norm][l2-norm] of every other element:
 
 ```javascript
 var x = [ 1.0, 2.0, 2.0, -7.0, -2.0, 3.0, 4.0, 2.0 ];
@@ -87,7 +87,7 @@ var z = gnrm2( 4, x1, 2 );
 // returns 5.0
 ```
 
-If either `N` or `stride` is less than or equal to `0`, the function returns `0`.
+If `N` is less than or equal to `0`, the function returns `0`.
 
 #### gnrm2.ndarray( N, x, stride, offset )
 
@@ -102,9 +102,9 @@ var z = gnrm2.ndarray( x.length, x, 1, 0 );
 
 The function has the following additional parameters:
 
--   **offset**: starting index for `x`.
+-   **offset**: starting index.
 
-While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying buffer, the `offset` parameter supports indexing semantics based on a starting index. For example, to calculate the [L2-norm][l2-norm] for every other value in `x` starting from the second value
+While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying buffer, the offset parameter supports indexing semantics based on a starting index. For example, to calculate the [L2-norm][l2-norm] for every other value in the strided array starting from the second value:
 
 ```javascript
 var x = [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ];
@@ -123,6 +123,7 @@ var z = gnrm2.ndarray( 4, x, 2, 1 );
 
 -   If `N <= 0`, both functions return `0.0`.
 -   `gnrm2()` corresponds to the [BLAS][blas] level 1 function [`dnrm2`][dnrm2] with the exception that this implementation works with any array type, not just Float64Arrays. Depending on the environment, the typed versions ([`dnrm2`][@stdlib/blas/base/dnrm2], [`snrm2`][@stdlib/blas/base/snrm2], etc.) are likely to be significantly more performant.
+-   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]).
 
 </section>
 
@@ -181,6 +182,8 @@ console.log( out );
 
 [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
+
 [@stdlib/blas/base/dnrm2]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/blas/base/dnrm2
 
 [@stdlib/blas/base/snrm2]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/blas/base/snrm2

lib/node_modules/@stdlib/blas/base/gnrm2/docs/repl.txt

@@ -2,13 +2,13 @@
 {{alias}}( N, x, stride )
     Computes the L2-norm of a vector.
 
-    The `N` and `stride` parameters determine which elements in `x` are accessed
-    at runtime.
+    The `N` and stride parameters determine which elements in the strided array
+    are accessed at runtime.
 
     Indexing is relative to the first index. To introduce an offset, use a typed
     array view.
 
-    If `N <= 0` or `stride <= 0`, the function returns `0`.
+    If `N <= 0`, the function returns `0`.
 
     Parameters
     ----------
@@ -19,7 +19,7 @@
         Input array.
 
     stride: integer
-        Index increment.
+        Stride length.
 
     Returns
     -------
@@ -49,8 +49,8 @@
     Computes the L2-norm of a vector using alternative indexing semantics.
 
     While typed array views mandate a view offset based on the underlying
-    buffer, the `offset` parameter supports indexing semantics based on a
-    starting index.
+    buffer, the offset parameter supports indexing semantics based on a starting
+    index.
 
     Parameters
     ----------
@@ -61,7 +61,7 @@
         Input array.
 
     stride: integer
-        Index increment.
+        Stride length.
 
     offset: integer
         Starting index.

lib/node_modules/@stdlib/blas/base/gnrm2/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 `gnrm2`.
@@ -40,7 +45,7 @@ interface Routine {
 	* var z = gnrm2( x.length, x, 1 );
 	* // returns 3.0
 	*/
-	( N: number, x: NumericArray, stride: number ): number;
+	( N: number, x: InputArray, stride: number ): number;
 
 	/**
 	* Computes the L2-norm of a vector using alternative indexing semantics.
@@ -57,7 +62,7 @@ interface Routine {
 	* var z = gnrm2.ndarray( x.length, x, 1, 0 );
 	* // returns 3.0
 	*/
-	ndarray( N: number, x: NumericArray, stride: number, offset: number ): number;
+	ndarray( N: number, x: InputArray, stride: number, offset: number ): number;
 }
 
 /**

lib/node_modules/@stdlib/blas/base/gnrm2/docs/types/test.ts

@@ -16,6 +16,7 @@
 * limitations under the License.
 */
 
+import AccessorArray = require( '@stdlib/array/base/accessor' );
 import gnrm2 = require( './index' );
 
 
@@ -26,6 +27,7 @@ import gnrm2 = require( './index' );
 	const x = new Float64Array( 10 );
 
 	gnrm2( x.length, x, 1 ); // $ExpectType number
+	gnrm2( 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 gnrm2 = require( './index' );
 	const x = new Float64Array( 10 );
 
 	gnrm2.ndarray( x.length, x, 1, 0 ); // $ExpectType number
+	gnrm2.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/base/gnrm2/lib/accessors.js

@@ -0,0 +1,90 @@
+/**
+* @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 sqrt = require( '@stdlib/math/base/special/sqrt' );
+var abs = require( '@stdlib/math/base/special/abs' );
+var pow = require( '@stdlib/math/base/special/pow' );
+
+
+// MAIN //
+
+/**
+* Computes the L2-norm of a vector.
+*
+* @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} stride - stride length
+* @param {NonNegativeInteger} offset - starting index
+* @returns {number} L2-norm
+*
+* @example
+* var toAccessorArray = require( '@stdlib/array/base/to-accessor-array' );
+* var arraylike2object = require( '@stdlib/array/base/arraylike2object' );
+*
+* var x = [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ];
+*
+* var z = gnrm2( 4, arraylike2object( toAccessorArray( x ) ), 2, 1 );
+* // returns 5.0
+*/
+function gnrm2( N, x, stride, offset ) {
+	var scale;
+	var buf;
+	var get;
+	var ssq;
+	var ax;
+	var ix;
+	var i;
+
+	buf = x.data;
+	get = x.accessors[ 0 ];
+
+	ix = offset;
+	if ( N === 1 ) {
+		return abs( get( buf, ix ) );
+	}
+	if ( stride === 0 ) {
+		return sqrt( N ) * abs( get( buf, ix ) );
+	}
+	scale = 0.0;
+	ssq = 1.0;
+	for ( i = 0; i < N; i++ ) {
+		if ( get( buf, ix ) !== 0.0 ) {
+			ax = abs( get( buf, ix ) );
+			if ( scale < ax ) {
+				ssq = 1.0 + ( ssq * pow( scale/ax, 2 ) );
+				scale = ax;
+			} else {
+				ssq += pow( ax/scale, 2 );
+			}
+		}
+		ix += stride;
+	}
+	return scale * sqrt( ssq );
+}
+
+
+// EXPORTS //
+
+module.exports = gnrm2;

lib/node_modules/@stdlib/blas/base/gnrm2/lib/index.js

@@ -32,13 +32,11 @@
 * // returns 3.0
 *
 * @example
-* var floor = require( '@stdlib/math/base/special/floor' );
 * var gnrm2 = require( '@stdlib/blas/base/gnrm2' );
 *
 * var x = [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ];
-* var N = floor( x.length / 2 );
 *
-* var z = gnrm2.ndarray( N, x, 2, 1 );
+* var z = gnrm2.ndarray( 4, x, 2, 1 );
 * // returns 5.0
 */
 

lib/node_modules/@stdlib/blas/base/gnrm2/lib/main.js

@@ -20,9 +20,8 @@
 
 // MODULES //
 
-var sqrt = require( '@stdlib/math/base/special/sqrt' );
-var abs = require( '@stdlib/math/base/special/abs' );
-var pow = require( '@stdlib/math/base/special/pow' );
+var stride2offset = require( '@stdlib/strided/base/stride2offset' );
+var ndarray = require( './ndarray.js' );
 
 
 // MAIN //
@@ -42,32 +41,7 @@ var pow = require( '@stdlib/math/base/special/pow' );
 * // returns 3.0
 */
 function gnrm2( N, x, stride ) {
-	var scale;
-	var ssq;
-	var ax;
-	var i;
-
-	if ( N <= 0 || stride <= 0 ) {
-		return 0.0;
-	}
-	if ( N === 1 ) {
-		return abs( x[ 0 ] );
-	}
-	scale = 0.0;
-	ssq = 1.0;
-	N *= stride;
-	for ( i = 0; i < N; i += stride ) {
-		if ( x[ i ] !== 0.0 ) {
-			ax = abs( x[ i ] );
-			if ( scale < ax ) {
-				ssq = 1.0 + ( ssq * pow( scale/ax, 2 ) );
-				scale = ax;
-			} else {
-				ssq += pow( ax/scale, 2 );
-			}
-		}
-	}
-	return scale * sqrt( ssq );
+	return ndarray( N, x, stride, stride2offset( N, stride ) );
 }
 
 

lib/node_modules/@stdlib/blas/base/gnrm2/lib/ndarray.js

@@ -20,9 +20,11 @@
 
 // MODULES //
 
+var arraylike2object = require( '@stdlib/array/base/arraylike2object' );
 var sqrt = require( '@stdlib/math/base/special/sqrt' );
 var abs = require( '@stdlib/math/base/special/abs' );
 var pow = require( '@stdlib/math/base/special/pow' );
+var accessors = require( './accessors.js' );
 
 
 // MAIN //
@@ -37,28 +39,35 @@ var pow = require( '@stdlib/math/base/special/pow' );
 * @returns {number} L2-norm
 *
 * @example
-* var floor = require( '@stdlib/math/base/special/floor' );
-*
 * var x = [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ];
-* var N = floor( x.length / 2 );
 *
-* var z = gnrm2( N, x, 2, 1 );
+* var z = gnrm2( 4, x, 2, 1 );
 * // returns 5.0
 */
 function gnrm2( N, x, stride, offset ) {
 	var scale;
 	var ssq;
 	var ax;
 	var ix;
+	var o;
 	var i;
 
 	if ( N <= 0 ) {
 		return 0.0;
 	}
-	if ( N === 1 ) {
-		return abs( x[ offset ] );
+
+	o = arraylike2object( x );
+	if ( o.accessorProtocol ) {
+		return accessors( N, o, stride, offset );
 	}
+
 	ix = offset;
+	if ( N === 1 ) {
+		return abs( x[ ix ] );
+	}
+	if ( stride === 0 ) {
+		return sqrt( N ) * abs( x[ ix ] );
+	}
 	scale = 0.0;
 	ssq = 1.0;
 	for ( i = 0; i < N; i++ ) {