119 lines
3.5 KiB
C++
119 lines
3.5 KiB
C++
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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/*
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* This file is part of the LibreOffice project.
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*
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*/
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#include <arraysumfunctor.hxx>
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#include <tools/simdsupport.hxx>
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#include <stdlib.h>
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#if SC_USE_SSE2
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namespace sc::op
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{
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/** Kahan sum with SSE2.
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*/
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static inline void sumSSE2(__m128d& sum, __m128d& err, const __m128d& value)
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{
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const __m128d ANNULATE_SIGN_BIT = _mm_castsi128_pd(_mm_set1_epi64x(0x7FFF'FFFF'FFFF'FFFF));
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// Temporal parameter
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__m128d t = _mm_add_pd(sum, value);
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// Absolute value of the total sum
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__m128d asum = _mm_and_pd(sum, ANNULATE_SIGN_BIT);
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// Absolute value of the value to add
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__m128d avalue = _mm_and_pd(value, ANNULATE_SIGN_BIT);
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// Compare the absolute values sum >= value
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__m128d mask = _mm_cmpge_pd(asum, avalue);
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// The following code has this form ( a - t + b)
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// Case 1: a = sum b = value
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// Case 2: a = value b = sum
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__m128d a = _mm_add_pd(_mm_and_pd(mask, sum), _mm_andnot_pd(mask, value));
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__m128d b = _mm_add_pd(_mm_and_pd(mask, value), _mm_andnot_pd(mask, sum));
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err = _mm_add_pd(err, _mm_add_pd(_mm_sub_pd(a, t), b));
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// Store result
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sum = t;
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}
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/** Execute Kahan sum with SSE2.
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*/
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KahanSum executeSSE2(size_t& i, size_t nSize, const double* pCurrent)
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{
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// Make sure we don't fall out of bounds.
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// This works by sums of 8 terms.
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// So the 8'th term is i+7
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// If we iterate until nSize won't fall out of bounds
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if (nSize > i + 7)
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{
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// Setup sums and errors as 0
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__m128d sum1 = _mm_setzero_pd();
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__m128d err1 = _mm_setzero_pd();
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__m128d sum2 = _mm_setzero_pd();
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__m128d err2 = _mm_setzero_pd();
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__m128d sum3 = _mm_setzero_pd();
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__m128d err3 = _mm_setzero_pd();
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__m128d sum4 = _mm_setzero_pd();
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__m128d err4 = _mm_setzero_pd();
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for (; i + 7 < nSize; i += 8)
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{
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// Kahan sum 1
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__m128d load1 = _mm_loadu_pd(pCurrent);
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sumSSE2(sum1, err1, load1);
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pCurrent += 2;
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// Kahan sum 2
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__m128d load2 = _mm_loadu_pd(pCurrent);
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sumSSE2(sum2, err2, load2);
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pCurrent += 2;
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// Kahan sum 3
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__m128d load3 = _mm_loadu_pd(pCurrent);
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sumSSE2(sum3, err3, load3);
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pCurrent += 2;
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// Kahan sum 4
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__m128d load4 = _mm_loadu_pd(pCurrent);
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sumSSE2(sum4, err4, load4);
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pCurrent += 2;
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}
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// Now we combine pairwise summation with Kahan summation
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// 1+2 3+4 -> 1, 3
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sumSSE2(sum1, err1, sum2);
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sumSSE2(sum1, err1, err2);
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sumSSE2(sum3, err3, sum4);
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sumSSE2(sum3, err3, err4);
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// 1+3 -> 1
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sumSSE2(sum1, err1, sum3);
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sumSSE2(sum1, err1, err3);
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// Store results
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double sums[2];
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double errs[2];
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_mm_storeu_pd(&sums[0], sum1);
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_mm_storeu_pd(&errs[0], err1);
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// First Kahan & pairwise summation
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// 0+1 -> 0
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KahanSum::sumNeumaierNormal(sums[0], errs[0], sums[1]);
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KahanSum::sumNeumaierNormal(sums[0], errs[0], errs[1]);
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// Store result
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return { sums[0], errs[0] };
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}
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return { 0.0, 0.0 };
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}
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} // namespace
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#endif
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/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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