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gdalgridavx.cpp
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/******************************************************************************
*
* Project: GDAL Gridding API.
* Purpose: Implementation of GDAL scattered data gridder.
* Author: Even Rouault, <even dot rouault at spatialys.com>
*
******************************************************************************
* Copyright (c) 2013, Even Rouault <even dot rouault at spatialys.com>
*
* SPDX-License-Identifier: MIT
****************************************************************************/
#include "gdalgrid.h"
#include "gdalgrid_priv.h"
#ifdef HAVE_AVX_AT_COMPILE_TIME
#include <immintrin.h>
/************************************************************************/
/* GDALGridInverseDistanceToAPower2NoSmoothingNoSearchAVX() */
/************************************************************************/
#define GDAL_mm256_load1_ps(x) _mm256_set_ps(x, x, x, x, x, x, x, x)
CPLErr GDALGridInverseDistanceToAPower2NoSmoothingNoSearchAVX(
const void *poOptions, GUInt32 nPoints,
CPL_UNUSED const double *unused_padfX,
CPL_UNUSED const double *unused_padfY,
CPL_UNUSED const double *unused_padfZ, double dfXPoint, double dfYPoint,
double *pdfValue, void *hExtraParamsIn)
{
size_t i = 0;
GDALGridExtraParameters *psExtraParams =
static_cast<GDALGridExtraParameters *>(hExtraParamsIn);
const float *pafX = psExtraParams->pafX;
const float *pafY = psExtraParams->pafY;
const float *pafZ = psExtraParams->pafZ;
const float fEpsilon = 0.0000000000001f;
const float fXPoint = static_cast<float>(dfXPoint);
const float fYPoint = static_cast<float>(dfYPoint);
const __m256 ymm_small = GDAL_mm256_load1_ps(fEpsilon);
const __m256 ymm_x = GDAL_mm256_load1_ps(fXPoint);
const __m256 ymm_y = GDAL_mm256_load1_ps(fYPoint);
__m256 ymm_nominator = _mm256_setzero_ps();
__m256 ymm_denominator = _mm256_setzero_ps();
int mask = 0;
#undef LOOP_SIZE
#if defined(__x86_64) || defined(_M_X64)
/* This would also work in 32bit mode, but there are only 8 XMM registers */
/* whereas we have 16 for 64bit */
#define LOOP_SIZE 16
size_t nPointsRound = (nPoints / LOOP_SIZE) * LOOP_SIZE;
for (i = 0; i < nPointsRound; i += LOOP_SIZE)
{
__m256 ymm_rx = _mm256_sub_ps(_mm256_load_ps(pafX + i),
ymm_x); /* rx = pafX[i] - fXPoint */
__m256 ymm_rx_8 = _mm256_sub_ps(_mm256_load_ps(pafX + i + 8), ymm_x);
__m256 ymm_ry = _mm256_sub_ps(_mm256_load_ps(pafY + i),
ymm_y); /* ry = pafY[i] - fYPoint */
__m256 ymm_ry_8 = _mm256_sub_ps(_mm256_load_ps(pafY + i + 8), ymm_y);
__m256 ymm_r2 = _mm256_add_ps(
_mm256_mul_ps(ymm_rx, ymm_rx), /* r2 = rx * rx + ry * ry */
_mm256_mul_ps(ymm_ry, ymm_ry));
__m256 ymm_r2_8 = _mm256_add_ps(_mm256_mul_ps(ymm_rx_8, ymm_rx_8),
_mm256_mul_ps(ymm_ry_8, ymm_ry_8));
__m256 ymm_invr2 = _mm256_rcp_ps(ymm_r2); /* invr2 = 1.0f / r2 */
__m256 ymm_invr2_8 = _mm256_rcp_ps(ymm_r2_8);
ymm_nominator =
_mm256_add_ps(ymm_nominator, /* nominator += invr2 * pafZ[i] */
_mm256_mul_ps(ymm_invr2, _mm256_load_ps(pafZ + i)));
ymm_nominator = _mm256_add_ps(
ymm_nominator,
_mm256_mul_ps(ymm_invr2_8, _mm256_load_ps(pafZ + i + 8)));
ymm_denominator = _mm256_add_ps(ymm_denominator,
ymm_invr2); /* denominator += invr2 */
ymm_denominator = _mm256_add_ps(ymm_denominator, ymm_invr2_8);
mask =
_mm256_movemask_ps(_mm256_cmp_ps(
ymm_r2, ymm_small, _CMP_LT_OS)) | /* if( r2 < fEpsilon) */
(_mm256_movemask_ps(_mm256_cmp_ps(ymm_r2_8, ymm_small, _CMP_LT_OS))
<< 8);
if (mask)
break;
}
#else
#define LOOP_SIZE 8
size_t nPointsRound = (nPoints / LOOP_SIZE) * LOOP_SIZE;
for (i = 0; i < nPointsRound; i += LOOP_SIZE)
{
__m256 ymm_rx =
_mm256_sub_ps(_mm256_load_ps(const_cast<float *>(pafX) + i),
ymm_x); /* rx = pafX[i] - fXPoint */
__m256 ymm_ry =
_mm256_sub_ps(_mm256_load_ps(const_cast<float *>(pafY) + i),
ymm_y); /* ry = pafY[i] - fYPoint */
__m256 ymm_r2 = _mm256_add_ps(
_mm256_mul_ps(ymm_rx, ymm_rx), /* r2 = rx * rx + ry * ry */
_mm256_mul_ps(ymm_ry, ymm_ry));
__m256 ymm_invr2 = _mm256_rcp_ps(ymm_r2); /* invr2 = 1.0f / r2 */
ymm_nominator = _mm256_add_ps(
ymm_nominator, /* nominator += invr2 * pafZ[i] */
_mm256_mul_ps(ymm_invr2,
_mm256_load_ps(const_cast<float *>(pafZ) + i)));
ymm_denominator = _mm256_add_ps(ymm_denominator,
ymm_invr2); /* denominator += invr2 */
mask = _mm256_movemask_ps(_mm256_cmp_ps(
ymm_r2, ymm_small, _CMP_LT_OS)); /* if( r2 < fEpsilon) */
if (mask)
break;
}
#endif
// Find which i triggered r2 < fEpsilon.
if (mask)
{
for (int j = 0; j < LOOP_SIZE; j++)
{
if (mask & (1 << j))
{
(*pdfValue) = (pafZ)[i + j];
// GCC and MSVC need explicit zeroing.
#if !defined(__clang__)
_mm256_zeroupper();
#endif
return CE_None;
}
}
}
#undef LOOP_SIZE
// Get back nominator and denominator values for YMM registers.
float afNominator[8];
float afDenominator[8];
_mm256_storeu_ps(afNominator, ymm_nominator);
_mm256_storeu_ps(afDenominator, ymm_denominator);
// MSVC doesn't emit AVX afterwards but may use SSE, so clear
// upper bits. Other compilers will continue using AVX for the
// below floating points operations.
#if defined(_MSC_FULL_VER)
_mm256_zeroupper();
#endif
float fNominator = afNominator[0] + afNominator[1] + afNominator[2] +
afNominator[3] + afNominator[4] + afNominator[5] +
afNominator[6] + afNominator[7];
float fDenominator = afDenominator[0] + afDenominator[1] +
afDenominator[2] + afDenominator[3] +
afDenominator[4] + afDenominator[5] +
afDenominator[6] + afDenominator[7];
// Do the few remaining loop iterations.
for (; i < nPoints; i++)
{
const float fRX = pafX[i] - fXPoint;
const float fRY = pafY[i] - fYPoint;
const float fR2 = fRX * fRX + fRY * fRY;
// If the test point is close to the grid node, use the point
// value directly as a node value to avoid singularity.
if (fR2 < 0.0000000000001)
{
break;
}
else
{
const float fInvR2 = 1.0f / fR2;
fNominator += fInvR2 * pafZ[i];
fDenominator += fInvR2;
}
}
if (i != nPoints)
{
(*pdfValue) = pafZ[i];
}
else if (fDenominator == 0.0)
{
(*pdfValue) =
static_cast<const GDALGridInverseDistanceToAPowerOptions *>(
poOptions)
->dfNoDataValue;
}
else
(*pdfValue) = fNominator / fDenominator;
// GCC needs explicit zeroing.
#if defined(__GNUC__) && !defined(__clang__)
_mm256_zeroupper();
#endif
return CE_None;
}
#endif /* HAVE_AVX_AT_COMPILE_TIME */