All files accessors.js

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100% Branches 16/16
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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.
*/
 
/* eslint-disable max-params, max-len */
 
'use strict';
 
// MODULES //
 
var isRowMajor = require( '@stdlib/ndarray/base/assert/is-row-major' );
 
 
// MAIN //
 
/**
* Generates a convolution matrix using accessor arrays.
*
* @private
* @param {PositiveInteger} k - number of rows in the output matrix
* @param {NonNegativeInteger} startRow - starting row offset
* @param {NonNegativeInteger} m - number of indexed elements in `x`
* @param {NonNegativeInteger} N - number of columns in the output matrix
* @param {Object} x - input array object
* @param {integer} strideX - stride length for `x`
* @param {NonNegativeInteger} offsetX - starting index for `x`
* @param {Object} out - output array object
* @param {integer} strideOut1 - stride length for the first dimension of `out`
* @param {integer} strideOut2 - stride length for the second dimension of `out`
* @param {NonNegativeInteger} offsetOut - starting index for `out`
* @returns {Object} output array object
*
* @example
* var toAccessorArray = require( '@stdlib/array/base/to-accessor-array' );
* var arraylike2object = require( '@stdlib/array/base/arraylike2object' );
*
* var x = [ 1.0, 2.0, 3.0 ];
* var out = [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ];
*
* gconvolutionMatrix( 5, 0, 3, 3, arraylike2object( toAccessorArray( x ) ), 1, 0, arraylike2object( toAccessorArray( out ) ), 3, 1, 0 );
* // out => [ 1.0, 0.0, 0.0, 2.0, 1.0, 0.0, 3.0, 2.0, 1.0, 0.0, 3.0, 2.0, 0.0, 0.0, 3.0 ]
*/
function gconvolutionMatrix( k, startRow, m, N, x, strideX, offsetX, out, strideOut1, strideOut2, offsetOut ) {
	var jstart;
	var istart;
	var jend;
	var iend;
	var xbuf;
	var obuf;
	var getX;
	var oset;
	var do0;
	var do1;
	var tmp;
	var io;
	var ix;
	var i;
	var j;
 
	xbuf = x.data;
	obuf = out.data;
	getX = x.accessors[ 0 ];
	oset = out.accessors[ 1 ];
 
	// Note on variable naming convention: S#, do#, io, i# where # corresponds to the loop number, with `0` being the innermost loop...
	if ( isRowMajor( [ strideOut1, strideOut2 ] ) ) {
		// Row-first iteration (inner loop walks columns):
		do0 = strideOut2;
		do1 = strideOut1 - ( N * strideOut2 );
		io = offsetOut;
		for ( i = 0; i < k; i++ ) {
			tmp = i + startRow;
 
			// Compute the valid column range:
			jstart = tmp - m + 1;
			if ( jstart < 0 ) {
				jstart = 0;
			}
			jend = tmp;
			if ( jend > N - 1 ) {
				jend = N - 1;
			}
			// Leading zeros:
			for ( j = 0; j < jstart; j++ ) {
				oset( obuf, io, 0.0 );
				io += do0;
			}
			// Values from `x` (index decreases as column increases):
			ix = offsetX + ( ( tmp - jstart ) * strideX );
			for ( j = jstart; j <= jend; j++ ) {
				oset( obuf, io, getX( xbuf, ix ) );
				ix -= strideX;
				io += do0;
			}
			// Trailing zeros:
			for ( j = jend + 1; j < N; j++ ) {
				oset( obuf, io, 0.0 );
				io += do0;
			}
			io += do1;
		}
	} else {
		// Column-first iteration (inner loop walks rows):
		do0 = strideOut1;
		do1 = strideOut2 - ( k * strideOut1 );
		io = offsetOut;
		for ( j = 0; j < N; j++ ) {
			// Compute the valid row range:
			istart = j - startRow;
			if ( istart < 0 ) {
				istart = 0;
			}
			iend = j - startRow + m - 1;
			if ( iend > k - 1 ) {
				iend = k - 1;
			}
			// Leading zeros:
			for ( i = 0; i < istart; i++ ) {
				oset( obuf, io, 0.0 );
				io += do0;
			}
			// Values from `x` (index increases as row increases):
			ix = offsetX + ( ( istart + startRow - j ) * strideX );
			for ( i = istart; i <= iend; i++ ) {
				oset( obuf, io, getX( xbuf, ix ) );
				ix += strideX;
				io += do0;
			}
			// Trailing zeros:
			for ( i = iend + 1; i < k; i++ ) {
				oset( obuf, io, 0.0 );
				io += do0;
			}
			io += do1;
		}
	}
	return out;
}
 
 
// EXPORTS //
 
module.exports = gconvolutionMatrix;