text: /**
  * @license Apache-2.0
  *
  * Copyright (c) 2020 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.
  */
  
  #include "stdlib/blas/ext/base/ssum.h"
  #include <stdint.h>
  #include <math.h>
  
  /**
  * Computes the sum of single-precision floating-point strided array elements.
  *
  * ## Method
  *
  * -   This implementation uses an "improved Kahan–Babuška algorithm", as described by Neumaier (1974).
  *
  * ## References
  *
  * -   Neumaier, Arnold. 1974. "Rounding Error Analysis of Some Methods for Summing Finite Sums." _Zeitschrift Für Angewandte Mathematik Und Mechanik_ 54 (1): 39–51. doi:[10.1002/zamm.19740540106](https://doi.org/10.1002/zamm.19740540106).
  *
  * @param N       number of indexed elements
  * @param X       input array
  * @param stride  stride length
  * @return        output value
  */
  float stdlib_strided_ssum( const int64_t N, const float *X, const int64_t stride ) {
  	int64_t ix;
  	int64_t i;
  	float sum;
  	float v;
  	float t;
  	float c;
  
  	if ( N <= 0 ) {
  		return 0.0f;
  	}
  	if ( N == 1 || stride == 0 ) {
  		return X[ 0 ];
  	}
  	if ( stride < 0 ) {
  		ix = (1-N) * stride;
  	} else {
  		ix = 0;
  	}
  	sum = 0.0f;
  	c = 0.0f;
  	for ( i = 0; i < N; i++ ) {
  		v = X[ ix ];
  		t = sum + v;
  		if ( fabsf( sum ) >= fabsf( v ) ) {
  			c += (sum-t) + v;
  		} else {
  			c += (v-t) + sum;
  		}
  		sum = t;
  		ix += stride;
  	}
  	return sum + c;
  }
  