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// Copyright (c) 2017-2023, University of Tennessee. All rights reserved.
// SPDX-License-Identifier: BSD-3-Clause
// This program is free software: you can redistribute it and/or modify it under
// the terms of the BSD 3-Clause license. See the accompanying LICENSE file.
#ifndef BLAS_ASUM_HH
#define BLAS_ASUM_HH
#include "blas/util.hh"
#include <limits>
namespace blas {
// =============================================================================
/// @return 1-norm of vector,
/// $|| Re(x) ||_1 + || Im(x) ||_1
/// = \sum_{i=0}^{n-1} |Re(x_i)| + |Im(x_i)|$.
///
/// Generic implementation for arbitrary data types.
///
/// @param[in] n
/// Number of elements in x. n >= 0.
///
/// @param[in] x
/// The n-element vector x, in an array of length (n-1)*incx + 1.
///
/// @param[in] incx
/// Stride between elements of x. incx > 0.
///
/// @ingroup asum
template <typename T>
real_type<T>
asum(
int64_t n,
T const *x, int64_t incx )
{
typedef real_type<T> real_t;
// check arguments
blas_error_if( n < 0 ); // standard BLAS returns, doesn't fail
blas_error_if( incx <= 0 ); // standard BLAS returns, doesn't fail
real_t result = 0;
if (incx == 1) {
// unit stride
for (int64_t i = 0; i < n; ++i) {
result += abs1( x[i] );
}
}
else {
// non-unit stride
int64_t ix = 0;
for (int64_t i = 0; i < n; ++i) {
result += abs1( x[ix] );
ix += incx;
}
}
return result;
}
} // namespace blas
#endif // #ifndef BLAS_ASUM_HH
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