time-to-botec

Benchmark sampling in different programming languages
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main.js (1880B)

      1 /**
      2 * @license Apache-2.0
      3 *
      4 * Copyright (c) 2018 The Stdlib Authors.
      5 *
      6 * Licensed under the Apache License, Version 2.0 (the "License");
      7 * you may not use this file except in compliance with the License.
      8 * You may obtain a copy of the License at
      9 *
     10 *    http://www.apache.org/licenses/LICENSE-2.0
     11 *
     12 * Unless required by applicable law or agreed to in writing, software
     13 * distributed under the License is distributed on an "AS IS" BASIS,
     14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     15 * See the License for the specific language governing permissions and
     16 * limitations under the License.
     17 */
     18 
     19 'use strict';
     20 
     21 // MODULES //
     22 
     23 var isSquareMatrix = require( './../../is-square-matrix' );
     24 
     25 
     26 // MAIN //
     27 
     28 /**
     29 * Tests if a value is a skew-symmetric matrix.
     30 *
     31 * ## Notes
     32 *
     33 * -   The implementation must rely on manually checking that \\(M_{ij} = -M_{ji}\\), and, while element access is deterministic, no way exists to prevent cache misses outside of reordering the underlying matrix elements, thus incurring a larger performance penalty than just "jumping around" in a single pass.
     34 * -   Worst case scenario: O(N^2).
     35 *
     36 * @param {*} v - value to test
     37 * @returns {boolean} boolean indicating if a value is a skew-symmetric matrix
     38 *
     39 * @example
     40 * var ndarray = require( '@stdlib/ndarray/ctor' );
     41 *
     42 * var arr = ndarray( 'generic', [ 0, -1, 1, 0 ], [ 2, 2 ], [ 2, 1 ], 0, 'row-major' );
     43 * var bool = isSkewSymmetricMatrix( arr );
     44 * // returns true
     45 *
     46 * bool = isSkewSymmetricMatrix( [] );
     47 * // returns false
     48 */
     49 function isSkewSymmetricMatrix( v ) {
     50 	var M;
     51 	var i;
     52 	var j;
     53 	if ( !isSquareMatrix( v ) ) {
     54 		return false;
     55 	}
     56 	M = v.shape[ 0 ];
     57 	for ( i = 0; i < M; i++ ) {
     58 		for ( j = 0; j <= i; j++ ) { // includes diagonal
     59 			if ( v.get( i, j ) !== -v.get( j, i ) ) {
     60 				return false;
     61 			}
     62 		}
     63 	}
     64 	return true;
     65 }
     66 
     67 
     68 // EXPORTS //
     69 
     70 module.exports = isSkewSymmetricMatrix;