feat: add blas/ext/last-index-of

lib/node_modules/@stdlib/blas/ext/last-index-of/README.md

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+<!--
+
+@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.
+
+-->
+
+# lastIndexOf
+
+> Return the last index of a specified search element along an [ndarray][@stdlib/ndarray/ctor] dimension.
+
+<section class="usage">
+
+## Usage
+
+```javascript
+var lastIndexOf = require( '@stdlib/blas/ext/last-index-of' );
+```
+
+#### lastIndexOf( x, searchElement\[, fromIndex]\[, options] )
+
+Returns the last index of a specified search element along an [ndarray][@stdlib/ndarray/ctor] dimension.
+
+```javascript
+var array = require( '@stdlib/ndarray/array' );
+
+// Create an input ndarray:
+var x = array( [ 1.0, 2.0, 3.0, 2.0, 5.0, 6.0 ] );
+// returns <ndarray>
+
+// Perform operation:
+var out = lastIndexOf( x, 2.0 );
+// returns <ndarray>
+
+var idx = out.get();
+// returns 3
+```
+
+The function has the following parameters:
+
+-   **x**: input [ndarray][@stdlib/ndarray/ctor]. Must have at least one dimension.
+-   **searchElement**: search element. May be either a scalar value or an [ndarray][@stdlib/ndarray/ctor]. If provided a scalar value, the value is cast to the data type of the input [ndarray][@stdlib/ndarray/ctor]. If provided an [ndarray][@stdlib/ndarray/ctor], the value must have a shape which is [broadcast-compatible][@stdlib/ndarray/base/broadcast-shapes] with the non-reduced dimensions of the input [ndarray][@stdlib/ndarray/ctor]. For example, given the input shape `[2, 3, 4]` and `options.dim=0`, the search element [ndarray][@stdlib/ndarray/ctor] must have a shape which is [broadcast-compatible][@stdlib/ndarray/base/broadcast-shapes] with the shape `[3, 4]`.
+-   **fromIndex**: index from which to begin searching (_optional_). May be either a scalar value or an [ndarray][@stdlib/ndarray/ctor] having an integer index or "generic" [data type][@stdlib/ndarray/dtypes]. If provided an [ndarray][@stdlib/ndarray/ctor], the value must have a shape which is [broadcast-compatible][@stdlib/ndarray/base/broadcast-shapes] with the non-reduced dimensions of the input [ndarray][@stdlib/ndarray/ctor]. For example, given the input shape `[2, 3, 4]` and `options.dim=0`, a provided [ndarray][@stdlib/ndarray/ctor] must have a shape which is [broadcast-compatible][@stdlib/ndarray/base/broadcast-shapes] with the shape `[3, 4]`. If provided a negative integer, the index at which to begin searching along a dimension is determined by counting backward from the last element (where `-1` refers to the last element). Default: `-1`.
+-   **options**: function options (_optional_).
+
+The function accepts the following options:
+
+-   **dtype**: output ndarray [data type][@stdlib/ndarray/dtypes]. Must be an integer index or generic [data type][@stdlib/ndarray/dtypes].
+-   **dim**: dimension over which to perform operation. If provided a negative integer, the dimension along which to perform the operation is determined by counting backward from the last dimension (where `-1` refers to the last dimension). Default: `-1`.
+-   **keepdims**: boolean indicating whether the reduced dimensions should be included in the returned [ndarray][@stdlib/ndarray/ctor] as singleton dimensions. Default: `false`.
+
+If the function is unable to find a search element along an [ndarray][@stdlib/ndarray/ctor], the corresponding element in the returned [ndarray][@stdlib/ndarray/ctor] is `-1`.
+
+```javascript
+var array = require( '@stdlib/ndarray/array' );
+
+// Create an input ndarray:
+var x = array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
+// returns <ndarray>
+
+// Perform operation:
+var out = lastIndexOf( x, 10.0 );
+// returns <ndarray>
+
+var idx = out.get();
+// returns -1
+```
+
+By default, the function begins searching from the last element along the reduction dimension. To begin searching from a different index, provide a `fromIndex` argument.
+
+```javascript
+var array = require( '@stdlib/ndarray/array' );
+
+// Create an input ndarray:
+var x = array( [ 1.0, 2.0, 3.0, 4.0, 2.0, 6.0 ] );
+// returns <ndarray>
+
+// Perform operation:
+var out = lastIndexOf( x, 2.0, 3 );
+// returns <ndarray>
+
+var idx = out.get();
+// returns 1
+```
+
+By default, the function performs the operation over elements in the last dimension. To perform the operation over a different dimension, provide a `dim` option.
+
+```javascript
+var ndarray2array = require( '@stdlib/ndarray/to-array' );
+var array = require( '@stdlib/ndarray/array' );
+
+var x = array( [ [ -3.0, 2.0 ], [ -3.0, 4.0 ] ] );
+
+var out = lastIndexOf( x, -3.0, {
+    'dim': 0
+});
+// returns <ndarray>
+
+var idx = ndarray2array( out );
+// returns [ 1, -1 ]
+```
+
+By default, the function excludes reduced dimensions from the output [ndarray][@stdlib/ndarray/ctor]. To include the reduced dimensions as singleton dimensions, set the `keepdims` option to `true`.
+
+```javascript
+var array = require( '@stdlib/ndarray/array' );
+var ndarray2array = require( '@stdlib/ndarray/to-array' );
+
+var x = array( [ [ -3.0, 2.0 ], [ -3.0, 4.0 ] ] );
+
+var opts = {
+    'dim': 0,
+    'keepdims': true
+};
+
+var out = lastIndexOf( x, -3.0, opts );
+// returns <ndarray>
+
+var idx = ndarray2array( out );
+// returns [ [ 1, -1 ] ]
+```
+
+By default, the function returns an [ndarray][@stdlib/ndarray/ctor] having a [data type][@stdlib/ndarray/dtypes] determined by the function's output data type [policy][@stdlib/ndarray/output-dtype-policies]. To override the default behavior, set the `dtype` option.
+
+```javascript
+var ndarray2array = require( '@stdlib/ndarray/to-array' );
+var dtype = require( '@stdlib/ndarray/dtype' );
+var array = require( '@stdlib/ndarray/array' );
+
+var x = array( [ 1.0, 2.0, 3.0, 4.0 ] );
+
+var idx = lastIndexOf( x, 2.0, {
+    'dtype': 'generic'
+});
+// returns <ndarray>
+
+var dt = dtype( idx );
+// returns 'generic'
+```
+
+#### lastIndexOf.assign( x, searchElement\[, fromIndex], out\[, options] )
+
+Returns the last index of a specified search element along an [ndarray][@stdlib/ndarray/ctor] dimension and assigns results to a provided output [ndarray][@stdlib/ndarray/ctor].
+
+```javascript
+var array = require( '@stdlib/ndarray/array' );
+var zeros = require( '@stdlib/ndarray/zeros' );
+
+var x = array( [ 1.0, 2.0, 3.0, 2.0, 5.0, 6.0 ] );
+var y = zeros( [], {
+    'dtype': 'int32'
+});
+
+var out = lastIndexOf.assign( x, 2.0, y );
+// returns <ndarray>
+
+var idx = out.get();
+// returns 3
+
+var bool = ( out === y );
+// returns true
+```
+
+The method has the following parameters:
+
+-   **x**: input [ndarray][@stdlib/ndarray/ctor]. Must have at least one dimension.
+-   **searchElement**: search element. May be either a scalar value or an [ndarray][@stdlib/ndarray/ctor]. If provided a scalar value, the value is cast to the data type of the input [ndarray][@stdlib/ndarray/ctor]. If provided an [ndarray][@stdlib/ndarray/ctor], the value must have a shape which is [broadcast-compatible][@stdlib/ndarray/base/broadcast-shapes] with the non-reduced dimensions of the input [ndarray][@stdlib/ndarray/ctor]. For example, given the input shape `[2, 3, 4]` and `options.dim=0`, the search element [ndarray][@stdlib/ndarray/ctor] must have a shape which is [broadcast-compatible][@stdlib/ndarray/base/broadcast-shapes] with the shape `[3, 4]`.
+-   **fromIndex**: index from which to begin searching (_optional_). May be either a scalar value or an [ndarray][@stdlib/ndarray/ctor] having an integer index or "generic" [data type][@stdlib/ndarray/dtypes]. If provided an [ndarray][@stdlib/ndarray/ctor], the value must have a shape which is [broadcast-compatible][@stdlib/ndarray/base/broadcast-shapes] with the non-reduced dimensions of the input [ndarray][@stdlib/ndarray/ctor]. For example, given the input shape `[2, 3, 4]` and `options.dim=0`, a provided [ndarray][@stdlib/ndarray/ctor] must have a shape which is [broadcast-compatible][@stdlib/ndarray/base/broadcast-shapes] with the shape `[3, 4]`. If provided a negative integer, the index at which to begin searching along a dimension is determined by counting backward from the last element (where `-1` refers to the last element). Default: `-1`.
+-   **out**: output [ndarray][@stdlib/ndarray/ctor].
+-   **options**: function options (_optional_).
+
+The method accepts the following options:
+
+-   **dim**: dimension over which to perform operation. If provided a negative integer, the dimension along which to perform the operation is determined by counting backward from the last dimension (where `-1` refers to the last dimension). Default: `-1`.
+
+</section>
+
+<!-- /.usage -->
+
+<section class="notes">
+
+## Notes
+
+-   Setting the `keepdims` option to `true` can be useful when wanting to ensure that the output [ndarray][@stdlib/ndarray/ctor] is [broadcast-compatible][@stdlib/ndarray/base/broadcast-shapes] with ndarrays having the same shape as the input [ndarray][@stdlib/ndarray/ctor].
+-   The output data type [policy][@stdlib/ndarray/output-dtype-policies] only applies to the main function and specifies that, by default, the function must return an [ndarray][@stdlib/ndarray/ctor] having an integer index or "generic" [data type][@stdlib/ndarray/dtypes]. For the `assign` method, the output [ndarray][@stdlib/ndarray/ctor] is allowed to have any supported output [data type][@stdlib/ndarray/dtypes].
+
+</section>
+
+<!-- /.notes -->
+
+<section class="examples">
+
+## Examples
+
+<!-- eslint no-undef: "error" -->
+
+```javascript
+var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
+var ndarray2array = require( '@stdlib/ndarray/to-array' );
+var ndarray = require( '@stdlib/ndarray/ctor' );
+var lastIndexOf = require( '@stdlib/blas/ext/last-index-of' );
+
+// Generate an array of random numbers:
+var xbuf = discreteUniform( 10, 0, 20, {
+    'dtype': 'float64'
+});
+
+// Wrap in an ndarray:
+var x = new ndarray( 'float64', xbuf, [ 5, 2 ], [ 2, 1 ], 0, 'row-major' );
+console.log( ndarray2array( x ) );
+
+// Perform operation:
+var idx = lastIndexOf( x, 10.0, {
+    'dim': 0
+});
+
+// Print the results:
+console.log( ndarray2array( idx ) );
+```
+
+</section>
+
+<!-- /.examples -->
+
+<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->
+
+<section class="related">
+
+</section>
+
+<!-- /.related -->
+
+<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="links">
+
+[@stdlib/ndarray/ctor]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/ndarray/ctor
+
+[@stdlib/ndarray/dtypes]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/ndarray/dtypes
+
+[@stdlib/ndarray/output-dtype-policies]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/ndarray/output-dtype-policies
+
+[@stdlib/ndarray/base/broadcast-shapes]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/ndarray/base/broadcast-shapes
+
+</section>
+
+<!-- /.links -->

lib/node_modules/@stdlib/blas/ext/last-index-of/benchmark/benchmark.assign.js

@@ -0,0 +1,113 @@
+/**
+* @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 bench = require( '@stdlib/bench' );
+var isnan = require( '@stdlib/math/base/assert/is-nan' );
+var pow = require( '@stdlib/math/base/special/pow' );
+var uniform = require( '@stdlib/random/array/uniform' );
+var zeros = require( '@stdlib/ndarray/zeros' );
+var ndarray = require( '@stdlib/ndarray/base/ctor' );
+var pkg = require( './../package.json' ).name;
+var lastIndexOf = require( './../lib' );
+
+
+// VARIABLES //
+
+var options = {
+	'dtype': 'float64'
+};
+
+
+// FUNCTIONS //
+
+/**
+* Creates a benchmark function.
+*
+* @private
+* @param {PositiveInteger} len - array length
+* @returns {Function} benchmark function
+*/
+function createBenchmark( len ) {
+	var out;
+	var x;
+
+	x = uniform( len, -50.0, 50.0, options );
+	x = new ndarray( options.dtype, x, [ len ], [ 1 ], 0, 'row-major' );
+
+	out = zeros( [], {
+		'dtype': 'int32'
+	});
+
+	return benchmark;
+
+	/**
+	* Benchmark function.
+	*
+	* @private
+	* @param {Benchmark} b - benchmark instance
+	*/
+	function benchmark( b ) {
+		var o;
+		var i;
+
+		b.tic();
+		for ( i = 0; i < b.iterations; i++ ) {
+			o = lastIndexOf.assign( x, 100.0, out );
+			if ( typeof o !== 'object' ) {
+				b.fail( 'should return an ndarray' );
+			}
+		}
+		b.toc();
+		if ( isnan( o.get() ) ) {
+			b.fail( 'should not return NaN' );
+		}
+		b.pass( 'benchmark finished' );
+		b.end();
+	}
+}
+
+
+// MAIN //
+
+/**
+* Main execution sequence.
+*
+* @private
+*/
+function main() {
+	var len;
+	var min;
+	var max;
+	var f;
+	var i;
+
+	min = 1; // 10^min
+	max = 6; // 10^max
+
+	for ( i = min; i <= max; i++ ) {
+		len = pow( 10, i );
+		f = createBenchmark( len );
+		bench( pkg+':assign:dtype='+options.dtype+',len='+len, f );
+	}
+}
+
+main();