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182 lines
6.9 KiB
Plaintext
182 lines
6.9 KiB
Plaintext
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/* Copyright (c) 2021, NVIDIA CORPORATION. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* * Neither the name of NVIDIA CORPORATION nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "common.h"
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#include <cooperative_groups.h>
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namespace cg = cooperative_groups;
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///////////////////////////////////////////////////////////////////////////////
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/// \brief one iteration of classical Horn-Schunck method, CUDA kernel.
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///
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/// It is one iteration of Jacobi method for a corresponding linear system.
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/// Template parameters are describe CTA size
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/// \param[in] du0 current horizontal displacement approximation
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/// \param[in] dv0 current vertical displacement approximation
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/// \param[in] Ix image x derivative
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/// \param[in] Iy image y derivative
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/// \param[in] Iz temporal derivative
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/// \param[in] w width
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/// \param[in] h height
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/// \param[in] s stride
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/// \param[in] alpha degree of smoothness
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/// \param[out] du1 new horizontal displacement approximation
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/// \param[out] dv1 new vertical displacement approximation
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///////////////////////////////////////////////////////////////////////////////
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template <int bx, int by>
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__global__ void JacobiIteration(const float *du0, const float *dv0,
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const float *Ix, const float *Iy,
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const float *Iz, int w, int h, int s,
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float alpha, float *du1, float *dv1) {
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// Handle to thread block group
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cg::thread_block cta = cg::this_thread_block();
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volatile __shared__ float du[(bx + 2) * (by + 2)];
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volatile __shared__ float dv[(bx + 2) * (by + 2)];
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const int ix = threadIdx.x + blockIdx.x * blockDim.x;
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const int iy = threadIdx.y + blockIdx.y * blockDim.y;
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// position within global memory array
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const int pos = min(ix, w - 1) + min(iy, h - 1) * s;
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// position within shared memory array
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const int shMemPos = threadIdx.x + 1 + (threadIdx.y + 1) * (bx + 2);
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// Load data to shared memory.
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// load tile being processed
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du[shMemPos] = du0[pos];
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dv[shMemPos] = dv0[pos];
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// load necessary neighbouring elements
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// We clamp out-of-range coordinates.
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// It is equivalent to mirroring
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// because we access data only one step away from borders.
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if (threadIdx.y == 0) {
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// beginning of the tile
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const int bsx = blockIdx.x * blockDim.x;
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const int bsy = blockIdx.y * blockDim.y;
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// element position within matrix
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int x, y;
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// element position within linear array
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// gm - global memory
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// sm - shared memory
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int gmPos, smPos;
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x = min(bsx + threadIdx.x, w - 1);
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// row just below the tile
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y = max(bsy - 1, 0);
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gmPos = y * s + x;
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smPos = threadIdx.x + 1;
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du[smPos] = du0[gmPos];
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dv[smPos] = dv0[gmPos];
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// row above the tile
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y = min(bsy + by, h - 1);
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smPos += (by + 1) * (bx + 2);
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gmPos = y * s + x;
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du[smPos] = du0[gmPos];
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dv[smPos] = dv0[gmPos];
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} else if (threadIdx.y == 1) {
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// beginning of the tile
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const int bsx = blockIdx.x * blockDim.x;
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const int bsy = blockIdx.y * blockDim.y;
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// element position within matrix
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int x, y;
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// element position within linear array
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// gm - global memory
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// sm - shared memory
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int gmPos, smPos;
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y = min(bsy + threadIdx.x, h - 1);
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// column to the left
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x = max(bsx - 1, 0);
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smPos = bx + 2 + threadIdx.x * (bx + 2);
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gmPos = x + y * s;
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// check if we are within tile
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if (threadIdx.x < by) {
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du[smPos] = du0[gmPos];
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dv[smPos] = dv0[gmPos];
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// column to the right
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x = min(bsx + bx, w - 1);
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gmPos = y * s + x;
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smPos += bx + 1;
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du[smPos] = du0[gmPos];
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dv[smPos] = dv0[gmPos];
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}
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}
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cg::sync(cta);
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if (ix >= w || iy >= h) return;
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// now all necessary data are loaded to shared memory
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int left, right, up, down;
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left = shMemPos - 1;
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right = shMemPos + 1;
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up = shMemPos + bx + 2;
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down = shMemPos - bx - 2;
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float sumU = (du[left] + du[right] + du[up] + du[down]) * 0.25f;
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float sumV = (dv[left] + dv[right] + dv[up] + dv[down]) * 0.25f;
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float frac = (Ix[pos] * sumU + Iy[pos] * sumV + Iz[pos]) /
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(Ix[pos] * Ix[pos] + Iy[pos] * Iy[pos] + alpha);
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du1[pos] = sumU - Ix[pos] * frac;
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dv1[pos] = sumV - Iy[pos] * frac;
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}
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///////////////////////////////////////////////////////////////////////////////
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/// \brief one iteration of classical Horn-Schunck method, CUDA kernel wrapper.
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///
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/// It is one iteration of Jacobi method for a corresponding linear system.
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/// \param[in] du0 current horizontal displacement approximation
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/// \param[in] dv0 current vertical displacement approximation
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/// \param[in] Ix image x derivative
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/// \param[in] Iy image y derivative
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/// \param[in] Iz temporal derivative
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/// \param[in] w width
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/// \param[in] h height
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/// \param[in] s stride
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/// \param[in] alpha degree of smoothness
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/// \param[out] du1 new horizontal displacement approximation
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/// \param[out] dv1 new vertical displacement approximation
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///////////////////////////////////////////////////////////////////////////////
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static void SolveForUpdate(const float *du0, const float *dv0, const float *Ix,
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const float *Iy, const float *Iz, int w, int h,
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int s, float alpha, float *du1, float *dv1) {
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// CTA size
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dim3 threads(32, 6);
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// grid size
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dim3 blocks(iDivUp(w, threads.x), iDivUp(h, threads.y));
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JacobiIteration<32, 6><<<blocks, threads>>>(du0, dv0, Ix, Iy, Iz, w, h, s,
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alpha, du1, dv1);
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}
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