83 lines
2.0 KiB
C
83 lines
2.0 KiB
C
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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2019 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/**
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* Compute the dot product of two double-precision floating-point vectors.
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*
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* @see <a href="http://www.netlib.org/lapack/expolore-html/df/d28/group__single__blas__level1.html">ddot</a>
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*/
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#include "stdlib/blas/base/ddot.h"
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/**
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* Computes the dot product of two double-precision floating-point vectors.
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*
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* @param N number of values over which to compute the dot product
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* @param X first array
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* @param strideX X stride length
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* @param Y second array
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* @param strideY Y stride length
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* @returns the dot product of X and Y
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*/
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double c_ddot( const int N, const double *X, const int strideX, const double *Y, const int strideY ) {
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double dot;
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int ix;
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int iy;
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int m;
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int i;
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dot = 0.0;
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if ( N <= 0 ) {
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return dot;
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}
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// If both strides are equal to `1`, use unrolled loops...
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if ( strideX == 1 && strideY == 1 ) {
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m = N % 5;
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// If we have a remainder, do a clean-up loop...
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if ( m > 0 ) {
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for ( i = 0; i < m; i++ ) {
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dot += X[ i ] * Y[ i ];
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}
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}
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if ( N < 5 ) {
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return dot;
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}
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for ( i = m; i < N; i += 5 ) {
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dot += ( X[i]*Y[i] ) + ( X[i+1]*Y[i+1] ) + ( X[i+2]*Y[i+2] ) + ( X[i+3]*Y[i+3] ) + ( X[i+4]*Y[i+4] );
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}
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return dot;
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}
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if ( strideX < 0 ) {
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ix = (1-N) * strideX;
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} else {
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ix = 0;
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}
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if ( strideY < 0 ) {
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iy = (1-N) * strideY;
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} else {
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iy = 0;
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}
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for ( i = 0; i < N; i++ ) {
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dot += X[ ix ] * Y[ iy ];
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ix += strideX;
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iy += strideY;
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}
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return dot;
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}
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