feat: add base implementation

Author: Pranavchiku

lib/node_modules/@stdlib/lapack/base/iladlr/lib/base.js

@@ -0,0 +1,92 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2024 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 isRowMajor = require( '@stdlib/ndarray/base/assert/is-row-major' );
+var max = require( '@stdlib/math/base/special/fast/max' );
+
+
+// MAIN //
+
+/**
+* Returns last non-zero row of matrix `A`.
+*
+* @private
+* @param {NonNegativeInteger} M - number of rows
+* @param {NonNegativeInteger} N - number of columns
+* @param {Float64Array} A - input matrix
+* @param {integer} strideA1 - stride of the first dimension of `A`
+* @param {integer} strideA2 - stride of the second dimension of `A`
+* @param {NonNegativeInteger} offsetA - starting index for `A`
+* @returns {integer} index of last non-zero row
+*
+* @example
+* var Float64Array = require( '@stdlib/array/float64' );
+*
+* var out;
+* var A = new Float64Array( [ 1.0, 2.0, 3.0, 4.0 ] );
+*
+* out = iladlr( 2, 2, A, 2, 1, 0 );
+* // returns 1
+*/
+function iladlr( M, N, A, strideA1, strideA2, offsetA ) {
+	var out;
+	var i;
+	var j;
+
+	if ( M === 0 ) {
+		return 0;
+	}
+	if ( isRowMajor( [ strideA1, strideA2 ] ) ) {
+		if ( A[ offsetA + ( ( M - 1 ) * strideA1 ) ] !== 0.0 || A[ offsetA + ( ( M - 1 ) * strideA1 ) + ( ( N - 1 ) * strideA2 ) ] ) {
+			return M - 1;
+		}
+		// Scan up each column tracking the last zero row seen.
+		out = -1;
+		for ( j = 0; j < N; j++ ) {
+			i = M - 1;
+			while ( i >= 0 && A[ offsetA + ( i * strideA1 ) + ( j * strideA2 ) ] === 0.0 ) {
+				i -= 1;
+			}
+			out = max( out, i );
+		}
+		return out;
+	}
+	// column-major
+	if ( A[ offsetA + ( ( M - 1 ) * strideA2 ) ] !== 0.0 || A[ offsetA + ( ( M - 1 ) * strideA2 ) + ( ( N - 1 ) * strideA1 ) ] ) {
+		return M - 1;
+	}
+	// Scan up each column tracking the last zero row seen.
+	out = -1;
+	for ( j = 0; j < N; j++ ) {
+		i = M - 1;
+		while ( i >= 0 && A[ offsetA + ( i * strideA2 ) + ( j * strideA1 ) ] === 0.0 ) {
+			i -= 1;
+		}
+		out = max( out, i );
+	}
+	return out;
+}
+
+
+// EXPORTS //
+
+module.exports = iladlr;