dapxsumors.c (1404B)
1 /** 2 * @license Apache-2.0 3 * 4 * Copyright (c) 2020 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 #include "stdlib/blas/ext/base/dapxsumors.h" 20 #include <stdint.h> 21 22 /** 23 * Adds a constant to each double-precision floating-point strided array element and computes the sum using ordinary recursive summation. 24 * 25 * @param N number of indexed elements 26 * @param alpha constant 27 * @param X input array 28 * @param stride stride length 29 * @return output value 30 */ 31 double stdlib_strided_dapxsumors( const int64_t N, const double alpha, const double *X, const int64_t stride ) { 32 double sum; 33 int64_t ix; 34 int64_t i; 35 36 if ( N <= 0 ) { 37 return 0.0; 38 } 39 if ( N == 1 || stride == 0 ) { 40 return alpha + X[ 0 ]; 41 } 42 if ( stride < 0 ) { 43 ix = (1-N) * stride; 44 } else { 45 ix = 0; 46 } 47 sum = 0.0; 48 for ( i = 0; i < N; i++ ) { 49 sum += alpha + X[ ix ]; 50 ix += stride; 51 } 52 return sum; 53 }