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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
* This file is part of the LibreOffice project.
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*
*/
#define LO_ARRAYSUM_SPACE AVX512
#include "arraysum.hxx"
#include <arraysumfunctorinternal.hxx>
#include <tools/simd.hxx>
#include <tools/simdsupport.hxx>
#include <stdlib.h>
namespace sc::op
{
#ifdef LO_AVX512F_AVAILABLE
bool hasAVX512FCode() { return true; }
using namespace AVX512;
/** Kahan sum with AVX512.
*/
static inline void sumAVX512(__m512d& sum, __m512d& err, const __m512d& value)
{
// Temporal parameter
__m512d t = _mm512_add_pd(sum, value);
// Absolute value of the total sum
__m512d asum = _mm512_abs_pd(sum);
// Absolute value of the value to add
__m512d avalue = _mm512_abs_pd(value);
// Compare the absolute values sum >= value
__mmask8 mask = _mm512_cmp_pd_mask(avalue, asum, _CMP_GE_OQ);
// The following code has this form ( a - t + b)
// Case 1: a = sum b = value
// Case 2: a = value b = sum
__m512d a = _mm512_mask_blend_pd(mask, sum, value);
__m512d b = _mm512_mask_blend_pd(mask, value, sum);
err = _mm512_add_pd(err, _mm512_add_pd(_mm512_sub_pd(a, t), b));
// Store result
sum = t;
}
/** Execute Kahan sum with AVX512.
*/
KahanSumSimple executeAVX512F(size_t& i, size_t nSize, const double* pCurrent)
{
// Make sure we don't fall out of bounds.
// This works by sums of 8 terms.
// So the 8'th term is i+7
// If we iterate until nSize won't fall out of bounds
if (nSize > i + 7)
{
// Setup sums and errors as 0
__m512d sum = _mm512_setzero_pd();
__m512d err = _mm512_setzero_pd();
// Sum the stuff
for (; i + 7 < nSize; i += 8)
{
// Kahan sum
__m512d load = _mm512_loadu_pd(pCurrent);
sumAVX512(sum, err, load);
pCurrent += 8;
}
// Store result
static_assert(sizeof(double) == 8);
double sums[8];
double errs[8];
_mm512_storeu_pd(&sums[0], sum);
_mm512_storeu_pd(&errs[0], err);
// First Kahan & pairwise summation
// 0+1 1+2 3+4 4+5 6+7 -> 0, 2, 4, 6
sumNeumanierNormal(sums[0], errs[0], sums[1]);
sumNeumanierNormal(sums[2], errs[2], sums[3]);
sumNeumanierNormal(sums[4], errs[4], sums[5]);
sumNeumanierNormal(sums[6], errs[6], sums[7]);
sumNeumanierNormal(sums[0], errs[0], errs[1]);
sumNeumanierNormal(sums[2], errs[2], errs[3]);
sumNeumanierNormal(sums[4], errs[4], errs[5]);
sumNeumanierNormal(sums[6], errs[6], errs[7]);
// Second Kahan & pairwise summation
// 0+2 4+6 -> 0, 4
sumNeumanierNormal(sums[0], errs[0], sums[2]);
sumNeumanierNormal(sums[4], errs[4], sums[6]);
sumNeumanierNormal(sums[0], errs[0], errs[2]);
sumNeumanierNormal(sums[4], errs[4], errs[6]);
// Third Kahan & pairwise summation
// 0+4 -> 0
sumNeumanierNormal(sums[0], errs[0], sums[4]);
sumNeumanierNormal(sums[0], errs[0], errs[4]);
// Return final result
return { sums[0], errs[0] };
}
return { 0.0, 0.0 };
}
#else // LO_AVX512F_AVAILABLE
bool hasAVX512FCode() { return false; }
KahanSumSimple executeAVX512F(size_t&, size_t, const double*) { abort(); }
#endif
} // end namespace sc::op
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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