feat: add lapack/base/dlamrg

lib/node_modules/@stdlib/lapack/base/dlamrg/README.md

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+<!--
+
+@license Apache-2.0
+
+Copyright (c) 2026 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.
+
+-->
+
+# dlamrg
+
+> Generates a permutation list to merge the entries of two independently sorted sets into a single set sorted in ascending order.
+
+<section class="usage">
+
+## Usage
+
+```javascript
+var dlamrg = require( '@stdlib/lapack/base/dlamrg' );
+```
+
+#### dlamrg( N1, N2, A, DTRD1, DTRD2, index )
+
+Generates a permutation list to merge the entries of two independently sorted sets into a single set sorted in ascending order.
+
+```javascript
+var Float64Array = require( '@stdlib/array/float64' );
+var Int32Array = require( '@stdlib/array/int32' );
+var dlamrg = require( '@stdlib/lapack/base/dlamrg' );
+
+var A = new Float64Array( [ 1.0, 3.0, 2.0, 4.0, 5.0 ] );
+var index = new Int32Array( 5 );
+dlamrg( 2, 3, A, 1, 1, index );
+// index => <Int32Array>[ 0, 2, 1, 3, 4 ]
+```
+
+The function has the following parameters:
+
+-   **N1**: the length of the first sorted list to be merged.
+-   **N2**: the length of the second sorted list to be merged.
+-   **A**: the array containing the first and the second sorted lists to be merged as a [`Float64Array`][mdn-float64array].
+-   **DTRD1**: stride for the first `N1` elements in `A`.
+-   **DTRD2**: stride for the last `N2` elements in `A`.
+-   **index**: the array containing the indices of elements of `A` such that they are in ascending order.
+
+Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.
+
+<!-- eslint-disable stdlib/capitalized-comments -->
+
+```javascript
+var Float64Array = require( '@stdlib/array/float64' );
+var Int32Array = require( '@stdlib/array/int32' );
+var dlamrg = require( '@stdlib/lapack/base/dlamrg' );
+
+var A = new Float64Array( [ 1.0, 3.0, 2.0, 4.0, 5.0 ] );
+
+// Initial array:
+var index0 = new Int32Array( 6 );
+
+// Create an offset view...
+var index1 = new Int32Array( index0.buffer, index0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
+
+dlamrg( 2, 3, A, 1, 1, index1 );
+// index0 => <Int32Array>[ 0, 0, 2, 1, 3, 4 ]
+```
+
+<!-- lint disable maximum-heading-length -->
+
+#### dlamrg.ndarray( N1, N2, A, sA, oA, DTRD1, DTRD2, index, sIndex, oIndex )
+
+Generates a permutation list to merge the entries of two independently sorted sets into a single set sorted in ascending order.
+
+```javascript
+var Float64Array = require( '@stdlib/array/float64' );
+var Int32Array = require( '@stdlib/array/int32' );
+var dlamrg = require( '@stdlib/lapack/base/dlamrg' );
+
+var A = new Float64Array( [ 1.0, 3.0, 2.0, 4.0, 5.0 ] );
+var index = new Int32Array( 5 );
+dlamrg.ndarray( 2, 3, A, 1, 0, 1, 1, index, 1, 0 );
+// index => <Int32Array>[ 0, 2, 1, 3, 4 ]
+```
+
+The function has the following additional parameters:
+
+-   **sA**: stride length for `A`.
+-   **oA**: starting index of `A`.
+-   **sIndex**: stride length for `index`.
+-   **oIndex**: starting index of `index`.
+
+While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying buffer, the offset parameters support indexing semantics based on starting indices. For example,
+
+```javascript
+var Float64Array = require( '@stdlib/array/float64' );
+var Int32Array = require( '@stdlib/array/int32' );
+var dlamrg = require( '@stdlib/lapack/base/dlamrg' );
+
+var A = new Float64Array( [ 999.9, 1.0, 3.0, 2.0, 4.0, 5.0 ] );
+var index = new Int32Array( 6 );
+dlamrg.ndarray( 2, 3, A, 1, 1, 1, 1, index, 1, 1 );
+// index => <Int32Array>[ 0, 1, 3, 2, 4, 5 ]
+```
+
+</section>
+
+<!-- /.usage -->
+
+<section class="notes">
+
+## Notes
+
+-   `dlamrg()` corresponds to the [LAPACK][lapack] routine [`dlamrg`][lapack-dlamrg].
+
+</section>
+
+<!-- /.notes -->
+
+<section class="examples">
+
+## Examples
+
+<!-- eslint no-undef: "error" -->
+
+```javascript
+var Float64Array = require( '@stdlib/array/float64' );
+var Int32Array = require( '@stdlib/array/int32' );
+var dlamrg = require( '@stdlib/lapack/base/dlamrg' );
+
+var A = new Float64Array( [ 1.0, 3.0, 2.0, 4.0, 5.0 ] );
+var index = new Int32Array( 5 );
+dlamrg( 2, 3, A, 1, 1, index );
+console.log( index );
+```
+
+</section>
+
+<!-- /.examples -->
+
+<!-- C interface documentation. -->
+
+* * *
+
+<section class="c">
+
+## C APIs
+
+<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
+
+<section class="intro">
+
+</section>
+
+<!-- /.intro -->
+
+<!-- C usage documentation. -->
+
+<section class="usage">
+
+### Usage
+
+```c
+TODO
+```
+
+#### TODO
+
+TODO.
+
+```c
+TODO
+```
+
+TODO
+
+```c
+TODO
+```
+
+</section>
+
+<!-- /.usage -->
+
+<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="notes">
+
+</section>
+
+<!-- /.notes -->
+
+<!-- C API usage examples. -->
+
+<section class="examples">
+
+### Examples
+
+```c
+TODO
+```
+
+</section>
+
+<!-- /.examples -->
+
+</section>
+
+<!-- /.c -->
+
+<!-- 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">
+
+[lapack]: https://www.netlib.org/lapack/explore-html/
+
+[lapack-dlamrg]: https://www.netlib.org/lapack/explore-html/dd/d91/group__lamrg_gac4d67a9ef55ca13be544488dfd5de1a7.html#gac4d67a9ef55ca13be544488dfd5de1a7
+
+[mdn-float64array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Float64Array
+
+[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
+
+</section>
+
+<!-- /.links -->

lib/node_modules/@stdlib/lapack/base/dlamrg/benchmark/benchmark.js

@@ -0,0 +1,120 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 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 uniform = require( '@stdlib/random/array/uniform' );
+var floor = require( '@stdlib/math/base/special/floor' );
+var pow = require( '@stdlib/math/base/special/pow' );
+var randu = require( '@stdlib/random/base/randu' );
+var Int32Array = require( '@stdlib/array/int32' );
+var isnan = require( '@stdlib/math/base/assert/is-nan' );
+var merge = require( '@stdlib/utils/merge' );
+var format = require( '@stdlib/string/format' );
+var pkg = require( './../package.json' ).name;
+var dlamrg = require( './../lib/dlamrg.js' );
+
+
+// VARIABLES //
+
+var options = {
+	'dtype': 'float64'
+};
+
+
+// FUNCTIONS //
+
+/**
+* Creates a benchmark function.
+*
+* @private
+* @param {PositiveInteger} len - array length
+* @returns {Function} benchmark function
+*/
+function createBenchmark( len ) {
+	var index = new Int32Array( len );
+	var N1 = floor( randu() * len );
+	var N2 = len - N1;
+	var A1 = uniform( N1, 0.0, 100.0, options );
+	var A2 = uniform( N2, 0.0, 100.0, options );
+	var A;
+
+	A1.sort(cmp);
+	A2.sort(cmp);
+
+	function cmp(a, b) {
+		return b - a;
+	}
+
+	A = merge( A1, A2 );
+	return benchmark;
+
+	/**
+	* Benchmark function.
+	*
+	* @private
+	* @param {Benchmark} b - benchmark instance
+	*/
+	function benchmark( b ) {
+		var i;
+
+		b.tic();
+		for ( i = 0; i < b.iterations; i++ ) {
+			dlamrg( N1, N2, A, 1, 1, index );
+			if ( isnan( index[ i%index.length ] ) ) {
+				b.fail( 'should not return NaN' );
+			}
+		}
+		b.toc();
+		if ( isnan( index[ i%index.length ] ) ) {
+			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( format( '%s:len=%d', pkg, len ), f );
+	}
+}
+
+main();