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/*
* Copyright (c) 2011, Michael Lehn
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1) Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2) Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3) Neither the name of the FLENS development group nor the names of
* its contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/* Based on
*
SUBROUTINE DLASSQ( N, X, INCX, SCALE, SUMSQ )
*
* -- LAPACK auxiliary routine (version 3.2) --
* -- LAPACK is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
* November 2006
*/
#ifndef FLENS_LAPACK_LA_LASSQ_TCC
#define FLENS_LAPACK_LA_LASSQ_TCC 1
#include <cxxstd/cmath.h>
#include <flens/blas/blas.h>
#include <flens/lapack/lapack.h>
namespace flens { namespace lapack {
//== generic lapack implementation =============================================
namespace generic {
template <typename VX, typename T>
void
lassq_impl(const DenseVector<VX> &x, T &scale, T &sumsq)
{
using std::abs;
typedef typename DenseVector<VX>::IndexType IndexType;
const IndexType n = x.length();
if (n>0) {
for (IndexType i=1; i<=n; ++i) {
if (x(i)!=T(0)) {
const T absXi = abs(x(i));
if (scale<absXi) {
sumsq = 1 + sumsq*pow(scale/absXi, 2);
scale = absXi;
} else {
sumsq += pow(absXi/scale, 2);
}
}
}
}
}
} // namespace generic
//== interface for native lapack ===============================================
#ifdef USE_CXXLAPACK
namespace external {
template <typename VX, typename T>
void
lassq_impl(const DenseVector<VX> &x, T &scale, T &sumsq)
{
cxxlapack::lassq(x.length(), x.data(), x.stride(), scale, sumsq);
}
} // namespace external
#endif // USE_CXXLAPACK
//== public interface ==========================================================
template <typename VX, typename T>
void
lassq(const DenseVector<VX> &x, T &scale, T &sumsq)
{
LAPACK_DEBUG_OUT("lassq");
//
// Test the input parameters
//
ASSERT(x.inc()>0);
//
// Make copies of output arguments
//
# ifdef CHECK_CXXLAPACK
T scale_ = scale;
T sumsq_ = sumsq;
# endif
//
// Call implementation
//
LAPACK_SELECT::lassq_impl(x, scale, sumsq);
# ifdef CHECK_CXXLAPACK
//
// Compare results
//
external::lassq_impl(x, scale_, sumsq_);
bool failed = false;
if (! isIdentical(scale, scale_, " scale", "scale_")) {
std::cerr << "CXXLAPACK: scale = " << scale << std::endl;
std::cerr << "F77LAPACK: scale_ = " << scale_ << std::endl;
failed = true;
}
if (! isIdentical(sumsq, sumsq_, " sumsq", "sumsq_")) {
std::cerr << "CXXLAPACK: sumsq = " << sumsq << std::endl;
std::cerr << "F77LAPACK: sumsq_ = " << sumsq_ << std::endl;
failed = true;
}
if (failed) {
ASSERT(0);
} else {
// std::cerr << "passed: lassq.tcc" << std::endl;
}
# endif
}
} } // namespace lapack, flens
#endif // FLENS_LAPACK_LA_LASSQ_TCC
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