// Theano op code
// Authors: Arjun Jain, Frederic Bastien, Jan Schluter
// Reference code: https://github.com/BVLC/caffe/blob/master/src/caffe/layers/conv_layer.cu
// and https://github.com/torch/cunn/blob/master/SpatialConvolutionMM.cu
// Adaptation for 3d
PyGpuArrayObject* corr3dMM(PyGpuArrayObject *const bottom,
PyGpuArrayObject *const weight,
PyGpuArrayObject *const top,
const size_t direction,
const size_t dH = 1,
const size_t dW = 1,
const size_t dD = 1,
const size_t dilH = 1,
const size_t dilW = 1,
const size_t dilD = 1,
const size_t padH = 0,
const size_t padW = 0,
const size_t padD = 0)
{
if (PyGpuArray_NDIM(bottom) != 5)
{
PyErr_SetString(PyExc_ValueError, "GpuCorr3dMM requires bottom of 5D");
return NULL;
}
if (!GpuArray_IS_C_CONTIGUOUS(&bottom->ga))
{
PyErr_Format(PyExc_ValueError,
"GpuCorr3dMM requires bottom to be C-contiguous, "
"but strides are: %ld %ld %ld %ld %ld\n",
PyGpuArray_STRIDES(bottom)[0],
PyGpuArray_STRIDES(bottom)[1],
PyGpuArray_STRIDES(bottom)[2],
PyGpuArray_STRIDES(bottom)[3],
PyGpuArray_STRIDES(bottom)[4]);
return NULL;
}
if (PyGpuArray_NDIM(weight) != 5)
{
PyErr_SetString(PyExc_ValueError, "GpuCorr3dMM requires weight of 5D");
return NULL;
}
if (!GpuArray_IS_C_CONTIGUOUS(&weight->ga))
{
PyErr_Format(PyExc_ValueError,
"GpuCorr3dMM requires weight to be C-contiguous, "
"but strides are: %ld %ld %ld %ld %ld\n",
PyGpuArray_STRIDES(weight)[0],
PyGpuArray_STRIDES(weight)[1],
PyGpuArray_STRIDES(weight)[2],
PyGpuArray_STRIDES(weight)[3],
PyGpuArray_STRIDES(weight)[4]);
return NULL;
}
if (PyGpuArray_NDIM(top) != 5)
{
PyErr_SetString(PyExc_ValueError, "GpuCorr3dMM requires top of 5D");
return NULL;
}
if (!GpuArray_IS_C_CONTIGUOUS(&top->ga))
{
PyErr_Format(PyExc_ValueError,
"GpuCorr3dMM requires top to be C-contiguous, "
"but strides are: %ld %ld %ld %ld %ld\n",
PyGpuArray_STRIDES(top)[0],
PyGpuArray_STRIDES(top)[1],
PyGpuArray_STRIDES(top)[2],
PyGpuArray_STRIDES(top)[3],
PyGpuArray_STRIDES(top)[4]);
return NULL;
}
// Extract some shape information for later and check shape consistency
// bottom: (batchSize, nChannels, bottomHeight, bottomWidth, bottomDepth)
const size_t batchSize = PyGpuArray_DIMS(bottom)[0];
const size_t nChannels = PyGpuArray_DIMS(bottom)[1];
const size_t bottomHeight = PyGpuArray_DIMS(bottom)[2];
const size_t bottomWidth = PyGpuArray_DIMS(bottom)[3];
const size_t bottomDepth = PyGpuArray_DIMS(bottom)[4];
// weights: (nFilters, nChannels, rows, columns, slices)
const size_t nFilters = PyGpuArray_DIMS(weight)[0];
const size_t kH = PyGpuArray_DIMS(weight)[2];
const size_t kW = PyGpuArray_DIMS(weight)[3];
const size_t kD = PyGpuArray_DIMS(weight)[4];
if (nChannels != PyGpuArray_DIMS(weight)[1]) {
PyErr_SetString(PyExc_ValueError,
"GpuCorr3dMM images and kernel must have the same stack size\n");
return NULL;
}
// implicit dilated filter
const size_t dil_kH = (kH - 1) * dilH + 1;
const size_t dil_kW = (kW - 1) * dilW + 1;
const size_t dil_kD = (kD - 1) * dilD + 1;
// top: (batchSize, nFilters, topHeight, topWidth, topDepth)
const size_t topHeight = (bottomHeight + 2*padH - dil_kH) / dH + 1;
const size_t topWidth = (bottomWidth + 2*padW - dil_kW) / dW + 1;
const size_t topDepth = (bottomDepth + 2*padD - dil_kD) / dD + 1;
if (batchSize != PyGpuArray_DIMS(top)[0] ||
nFilters != PyGpuArray_DIMS(top)[1] ||
topHeight != PyGpuArray_DIMS(top)[2] ||
topWidth != PyGpuArray_DIMS(top)[3] ||
topDepth != PyGpuArray_DIMS(top)[4]) {
PyErr_Format(PyExc_ValueError,
"GpuCorr3dMM shape inconsistency:\n"
" bottom shape: %ld %ld %ld %ld %ld\n"
" weight shape: %ld %ld %ld %ld %ld\n"
" top shape: %ld %ld %ld %ld %ld (expected %ld %ld %ld %ld %ld)\n",
batchSize, nChannels, bottomHeight, bottomWidth, bottomDepth,
nFilters, nChannels, kH, kW, kD,
PyGpuArray_DIMS(top)[0], PyGpuArray_DIMS(top)[1],
PyGpuArray_DIMS(top)[2], PyGpuArray_DIMS(top)[3], PyGpuArray_DIMS(top)[4],
batchSize, nFilters, topHeight, topWidth, topDepth);
return NULL;
}
int err = gpublas_setup(bottom->context->ctx);
if (err != GA_NO_ERROR) {
PyErr_SetString(PyExc_RuntimeError, "Can't setup blas");
return NULL;
}
// Get the max threads per blocks
size_t max_threads_dim;
err = gpucontext_property(bottom->context->ctx, GA_CTX_PROP_MAXLSIZE, &max_threads_dim);
if (err != GA_NO_ERROR){
PyErr_Format(PyExc_RuntimeError,
"Could not fetch max_threads_dim.");
return NULL;
}
// Create temporary columns
size_t col_dim[2];
col_dim[0] = nChannels * kW * kH * kD;
col_dim[1] = topHeight * topWidth * topDepth;
PyGpuArrayObject* col = (PyGpuArrayObject*)pygpu_empty(2, col_dim,
bottom->ga.typecode,
GA_C_ORDER,
bottom->context,
Py_None);
if (NULL == col)
{
PyErr_Format(PyExc_RuntimeError,
"GpuCorr3dMM failed to allocate working memory of %ld x %ld\n",
col_dim[0], col_dim[1]);
return NULL;
}
// Define some useful variables
const size_t bottom_stride = PyGpuArray_STRIDES(bottom)[0] / gpuarray_get_elsize(bottom->ga.typecode);
const size_t top_stride = PyGpuArray_STRIDES(top)[0] / gpuarray_get_elsize(top->ga.typecode);
const size_t K_ = col_dim[0];
const size_t N_ = col_dim[1];
const size_t M_ = nFilters;
const DTYPE_INPUT_0 one = 1.0f;
const DTYPE_INPUT_0 zero = 0.0f;
PyGpuArrayObject *output;
if (direction == 0) { // forward pass
output = top;
// valid correlation: im3d2col, then gemm
// Iterate over batch
for (size_t n = 0; n < batchSize; n++) {
// First, im3d2col
err = im3d2col(max_threads_dim,
bottom->ga.data, n * bottom_stride, nChannels, bottomHeight,
bottomWidth, bottomDepth, kH, kW, kD, dilH, dilW, dilD,
padH, padW, padD, dH, dW, dD, col->ga.data);
if (err != GA_NO_ERROR) {
Py_DECREF(col);
return NULL;
}
// Second, gemm
err = gpublas_sgemm(cb_fortran, cb_no_trans, cb_no_trans,
N_, M_, K_, one,
col->ga.data, 0, N_,
weight->ga.data, 0, K_,
zero,
top->ga.data, n * top_stride, N_);
if (err != GA_NO_ERROR) {
PyErr_Format(PyExc_RuntimeError,
"GpuCorr3dMM encountered an error running sgemm.\n");
Py_DECREF(col);
return NULL;
}
}
}
else if (direction == 1) { // backprop wrt. weights
output = weight;
// valid convolution: im3col, then gemm
// Iterate over batch
for (size_t n = 0; n < batchSize; n++) {
// First, im3d2col
err = im3d2col(max_threads_dim,
bottom->ga.data, n * bottom_stride, nChannels, bottomHeight,
bottomWidth, bottomDepth, kH, kW, kD, dilH, dilW, dilD,
padH, padW, padD, dH, dW, dD, col->ga.data);
if (err != GA_NO_ERROR) {
Py_DECREF(col);
return NULL;
}
// Second, gemm
// Note that we accumulate into weight. We do so by setting beta = 0
// for the first iteration and beta = 1 for subsequent ones. (This
// is faster than setting weight to all zeros before the loop.)
err = gpublas_sgemm(cb_fortran, cb_trans, cb_no_trans,
K_, M_, N_, one,
col->ga.data, 0, N_,
top->ga.data, n * top_stride, N_,
(n == 0) ? zero : one,
weight->ga.data, 0, K_);
if (err != GA_NO_ERROR) {
PyErr_Format(PyExc_RuntimeError,
"GpuCorr3dMM encountered an error running sgemm.\n");
Py_DECREF(col);
return NULL;
}
}
}
else if (direction == 2) { // backprop wrt. inputs
output = bottom;
// full convolution: gemm, then col2im3d
// Iterate over batch
for (size_t n = 0; n < batchSize; n++) {
// gemm into columns
err = gpublas_sgemm(cb_fortran, cb_no_trans, cb_trans,
N_, K_, M_, one,
top->ga.data, n * top_stride, N_,
weight->ga.data, 0, K_,
zero,
col->ga.data, 0, N_);
if (err != GA_NO_ERROR) {
PyErr_Format(PyExc_RuntimeError,
"GpuCorr3dMM encountered an error running sgemm.\n");
Py_DECREF(col);
return NULL;
}
// col2im3d back to the data
err = col2im3d(max_threads_dim,
col->ga.data, nChannels,
bottomHeight, bottomWidth, bottomDepth,
kH, kW, kD, dilH, dilW, dilD, padH, padW, padD,
dH, dW, dD, bottom->ga.data, n * bottom_stride);
if (err != GA_NO_ERROR) {
Py_DECREF(col);
return NULL;
}
}
}
// Free temporary columns
Py_DECREF(col);
// Note that we don't change the refcount of the output matrix here. Output
// (re)allocation and refcounting is done in BaseGpuCorr3dMM.c_code_helper();
// in here output is just aliased to one of bottom, weights, or top.
return output;
}
// Theano op code
// Authors: Arjun Jain, Frederic Bastien, Jan Schluter
// Reference code: https://github.com/BVLC/caffe/blob/master/src/caffe/layers/conv_layer.cu
// and https://github.com/torch/cunn/blob/master/SpatialConvolutionMM.cu
// Adaptation for 3d
PyGpuArrayObject* corr3dMM(PyGpuArrayObject *const bottom,
PyGpuArrayObject *const weight,
PyGpuArrayObject *const top,
const size_t direction,
const size_t dH = 1,
const size_t dW = 1,
const size_t dD = 1,
const size_t dilH = 1,
const size_t dilW = 1,
const size_t dilD = 1,
const size_t padH = 0,
const size_t padW = 0,
const size_t padD = 0)
{
if (PyGpuArray_NDIM(bottom) != 5)
{
PyErr_SetString(PyExc_ValueError, "GpuCorr3dMM requires bottom of 5D");
return NULL;
}
if (!GpuArray_IS_C_CONTIGUOUS(&bottom->ga))
{
PyErr_Format(PyExc_ValueError,
"GpuCorr3dMM requires bottom to be C-contiguous, "
"but strides are: %ld %ld %ld %ld %ld\n",
PyGpuArray_STRIDES(bottom)[0],
PyGpuArray_STRIDES(bottom)[1],
PyGpuArray_STRIDES(bottom)[2],
PyGpuArray_STRIDES(bottom)[3],
PyGpuArray_STRIDES(bottom)[4]);
return NULL;
}
if (PyGpuArray_NDIM(weight) != 5)
{
PyErr_SetString(PyExc_ValueError, "GpuCorr3dMM requires weight of 5D");
return NULL;
}
if (!GpuArray_IS_C_CONTIGUOUS(&weight->ga))
{
PyErr_Format(PyExc_ValueError,
"GpuCorr3dMM requires weight to be C-contiguous, "
"but strides are: %ld %ld %ld %ld %ld\n",
PyGpuArray_STRIDES(weight)[0],
PyGpuArray_STRIDES(weight)[1],
PyGpuArray_STRIDES(weight)[2],
PyGpuArray_STRIDES(weight)[3],
PyGpuArray_STRIDES(weight)[4]);
return NULL;
}
if (PyGpuArray_NDIM(top) != 5)
{
PyErr_SetString(PyExc_ValueError, "GpuCorr3dMM requires top of 5D");
return NULL;
}
if (!GpuArray_IS_C_CONTIGUOUS(&top->ga))
{
PyErr_Format(PyExc_ValueError,
"GpuCorr3dMM requires top to be C-contiguous, "
"but strides are: %ld %ld %ld %ld %ld\n",
PyGpuArray_STRIDES(top)[0],
PyGpuArray_STRIDES(top)[1],
PyGpuArray_STRIDES(top)[2],
PyGpuArray_STRIDES(top)[3],
PyGpuArray_STRIDES(top)[4]);
return NULL;
}
// Extract some shape information for later and check shape consistency
// bottom: (batchSize, nChannels, bottomHeight, bottomWidth, bottomDepth)
const size_t batchSize = PyGpuArray_DIMS(bottom)[0];
const size_t nChannels = PyGpuArray_DIMS(bottom)[1];
const size_t bottomHeight = PyGpuArray_DIMS(bottom)[2];
const size_t bottomWidth = PyGpuArray_DIMS(bottom)[3];
const size_t bottomDepth = PyGpuArray_DIMS(bottom)[4];
// weights: (nFilters, nChannels, rows, columns, slices)
const size_t nFilters = PyGpuArray_DIMS(weight)[0];
const size_t kH = PyGpuArray_DIMS(weight)[2];
const size_t kW = PyGpuArray_DIMS(weight)[3];
const size_t kD = PyGpuArray_DIMS(weight)[4];
if (nChannels != PyGpuArray_DIMS(weight)[1]) {
PyErr_SetString(PyExc_ValueError,
"GpuCorr3dMM images and kernel must have the same stack size\n");
return NULL;
}
// implicit dilated filter
const size_t dil_kH = (kH - 1) * dilH + 1;
const size_t dil_kW = (kW - 1) * dilW + 1;
const size_t dil_kD = (kD - 1) * dilD + 1;
// top: (batchSize, nFilters, topHeight, topWidth, topDepth)
const size_t topHeightNoDH = (bottomHeight + 2*padH - dil_kH);
const size_t topWidthNoDW = (bottomWidth + 2*padW - dil_kW);
const size_t topDepthNoDD = (bottomDepth + 2*padD - dil_kD);
// the above values might be negative so we need to use Python-like
// flooring integer division to be compatible with get_conv_output.
// note: this macro implements Python's // for negative x only
#define _CONV_FLOORDIV_X(x,y) ((x < 0) ? (- ((-x) / y) - (((-x) % y) == 0 ? 0 : 1)) : (x / y))
const size_t topHeight = _CONV_FLOORDIV_X(topHeightNoDH, dH) + 1;
const size_t topWidth = _CONV_FLOORDIV_X(topWidthNoDW, dW) + 1;
const size_t topDepth = _CONV_FLOORDIV_X(topDepthNoDD, dD) + 1;
#undef _CONV_FLOORDIV
if (batchSize != PyGpuArray_DIMS(top)[0] ||
nFilters != PyGpuArray_DIMS(top)[1] ||
topHeight != PyGpuArray_DIMS(top)[2] ||
topWidth != PyGpuArray_DIMS(top)[3] ||
topDepth != PyGpuArray_DIMS(top)[4]) {
PyErr_Format(PyExc_ValueError,
"GpuCorr3dMM shape inconsistency:\n"
" bottom shape: %ld %ld %ld %ld %ld\n"
" weight shape: %ld %ld %ld %ld %ld\n"
" top shape: %ld %ld %ld %ld %ld (expected %ld %ld %ld %ld %ld)\n",
batchSize, nChannels, bottomHeight, bottomWidth, bottomDepth,
nFilters, nChannels, kH, kW, kD,
PyGpuArray_DIMS(top)[0], PyGpuArray_DIMS(top)[1],
PyGpuArray_DIMS(top)[2], PyGpuArray_DIMS(top)[3], PyGpuArray_DIMS(top)[4],
batchSize, nFilters, topHeight, topWidth, topDepth);
return NULL;
}
int err = gpublas_setup(bottom->context->ctx);
if (err != GA_NO_ERROR) {
PyErr_SetString(PyExc_RuntimeError, "Can't setup blas");
return NULL;
}
// Create temporary columns
size_t col_dim[2];
col_dim[0] = nChannels * kW * kH * kD;
col_dim[1] = topHeight * topWidth * topDepth;
PyGpuArrayObject* col = (PyGpuArrayObject*)pygpu_empty(2, col_dim,
bottom->ga.typecode,
GA_C_ORDER,
bottom->context,
Py_None);
if (NULL == col)
{
PyErr_Format(PyExc_RuntimeError,
"GpuCorr3dMM failed to allocate working memory of %ld x %ld\n",
col_dim[0], col_dim[1]);
return NULL;
}
// Define some useful variables
const size_t bottom_stride = PyGpuArray_STRIDES(bottom)[0] / gpuarray_get_elsize(bottom->ga.typecode);
const size_t top_stride = PyGpuArray_STRIDES(top)[0] / gpuarray_get_elsize(top->ga.typecode);
const size_t K_ = col_dim[0];
const size_t N_ = col_dim[1];
const size_t M_ = nFilters;
PyGpuArrayObject *output;
if (direction == 0) { // forward pass
output = top;
if (batchSize == 0 || nChannels == 0 || nFilters == 0) {
err = GpuArray_memset(&output->ga, 0);
if (err != GA_NO_ERROR) {
PyErr_Format(PyExc_RuntimeError,
"GpuCorr3dMM could not fill the output with zeros: %d", err);
Py_DECREF(col);
return NULL;
}
Py_DECREF(col);
return output;
}
// valid correlation: im3d2col, then gemm
// Iterate over batch
for (size_t n = 0; n < batchSize; n++) {
// First, im3d2col
err = im3d2col(
bottom->ga.data, n * bottom_stride, nChannels, bottomHeight,
bottomWidth, bottomDepth, kH, kW, kD, dilH, dilW, dilD,
padH, padW, padD, dH, dW, dD, col->ga.data);
if (err != GA_NO_ERROR) {
Py_DECREF(col);
return NULL;
}
// Second, gemm
switch (col->ga.typecode) {
case GA_FLOAT:
err = gpublas_sgemm(cb_fortran, cb_no_trans, cb_no_trans,
N_, M_, K_, 1,
col->ga.data, 0, N_,
weight->ga.data, 0, K_,
0,
top->ga.data, n * top_stride, N_);
break;
case GA_DOUBLE:
err = gpublas_dgemm(cb_fortran, cb_no_trans, cb_no_trans,
N_, M_, K_, 1,
col->ga.data, 0, N_,
weight->ga.data, 0, K_,
0,
top->ga.data, n * top_stride, N_);
break;
case GA_HALF:
err = gpublas_hgemm(cb_fortran, cb_no_trans, cb_no_trans,
N_, M_, K_, 1,
col->ga.data, 0, N_,
weight->ga.data, 0, K_,
0,
top->ga.data, n * top_stride, N_);
break;
default:
err = GA_UNSUPPORTED_ERROR;
}
if (err != GA_NO_ERROR) {
PyErr_Format(PyExc_RuntimeError,
"GpuCorr3dMM forward encountered an error running gemm.");
Py_DECREF(col);
return NULL;
}
}
}
else if (direction == 1) { // backprop wrt. weights
output = weight;
if (batchSize == 0 || nChannels == 0 || nFilters == 0) {
err = GpuArray_memset(&output->ga, 0);
if (err != GA_NO_ERROR) {
PyErr_Format(PyExc_RuntimeError,
"GpuCorr3dMM grad wrt. weights could not fill the output with zeros: %d", err);
Py_DECREF(col);
return NULL;
}
Py_DECREF(col);
return output;
}
// valid convolution: im3col, then gemm
// Iterate over batch
for (size_t n = 0; n < batchSize; n++) {
// First, im3d2col
err = im3d2col(
bottom->ga.data, n * bottom_stride, nChannels, bottomHeight,
bottomWidth, bottomDepth, kH, kW, kD, dilH, dilW, dilD,
padH, padW, padD, dH, dW, dD, col->ga.data);
if (err != GA_NO_ERROR) {
Py_DECREF(col);
return NULL;
}
// Second, gemm
// Note that we accumulate into weight. We do so by setting beta = 0
// for the first iteration and beta = 1 for subsequent ones. (This
// is faster than setting weight to all zeros before the loop.)
switch (col->ga.typecode) {
case GA_FLOAT:
err = gpublas_sgemm(cb_fortran, cb_trans, cb_no_trans,
K_, M_, N_, 1,
col->ga.data, 0, N_,
top->ga.data, n * top_stride, N_,
(n == 0) ? 0 : 1,
weight->ga.data, 0, K_);
break;
case GA_DOUBLE:
err = gpublas_dgemm(cb_fortran, cb_trans, cb_no_trans,
K_, M_, N_, 1,
col->ga.data, 0, N_,
top->ga.data, n * top_stride, N_,
(n == 0) ? 0 : 1,
weight->ga.data, 0, K_);
break;
case GA_HALF:
err = gpublas_hgemm(cb_fortran, cb_trans, cb_no_trans,
K_, M_, N_, 1,
col->ga.data, 0, N_,
top->ga.data, n * top_stride, N_,
(n == 0) ? 0 : 1,
weight->ga.data, 0, K_);
break;
default:
err = GA_UNSUPPORTED_ERROR;
}
if (err != GA_NO_ERROR) {
PyErr_Format(PyExc_RuntimeError,
"GpuCorr3dMM grad weights encountered an error running gemm.");
Py_DECREF(col);
return NULL;
}
}
if (batchSize == 0) {
err = GpuArray_memset(&weight->ga, 0);
if (err != GA_NO_ERROR) {
PyErr_Format(PyExc_RuntimeError,
"GpuCorr3dMM grad weights could not fill the output with zeros: %d", err);
Py_DECREF(col);
return NULL;
}
}
}
else if (direction == 2) { // backprop wrt. inputs
output = bottom;
if (batchSize == 0 || nChannels == 0 || nFilters == 0) {
err = GpuArray_memset(&output->ga, 0);
if (err != GA_NO_ERROR) {
PyErr_Format(PyExc_RuntimeError,
"GpuCorr3dMM grad wrt. inputs could not fill the output with zeros: %d", err);
Py_DECREF(col);
return NULL;
}
Py_DECREF(col);
return output;
}
// full convolution: gemm, then col2im3d
// Iterate over batch
for (size_t n = 0; n < batchSize; n++) {
// gemm into columns
switch (top->ga.typecode) {
case GA_FLOAT:
err = gpublas_sgemm(cb_fortran, cb_no_trans, cb_trans,
N_, K_, M_, 1,
top->ga.data, n * top_stride, N_,
weight->ga.data, 0, K_,
0,
col->ga.data, 0, N_);
break;
case GA_DOUBLE:
err = gpublas_dgemm(cb_fortran, cb_no_trans, cb_trans,
N_, K_, M_, 1,
top->ga.data, n * top_stride, N_,
weight->ga.data, 0, K_,
0,
col->ga.data, 0, N_);
break;
case GA_HALF:
err = gpublas_hgemm(cb_fortran, cb_no_trans, cb_trans,
N_, K_, M_, 1,
top->ga.data, n * top_stride, N_,
weight->ga.data, 0, K_,
0,
col->ga.data, 0, N_);
break;
default:
err = GA_UNSUPPORTED_ERROR;
}
if (err != GA_NO_ERROR) {
PyErr_Format(PyExc_RuntimeError,
"GpuCorr3dMM grad inputs encountered an error running gemm.");
Py_DECREF(col);
return NULL;
}
// col2im3d back to the data
err = col2im3d(col->ga.data, nChannels,
bottomHeight, bottomWidth, bottomDepth,
kH, kW, kD, dilH, dilW, dilD, padH, padW, padD,
dH, dW, dD, bottom->ga.data, n * bottom_stride);
if (err != GA_NO_ERROR) {
Py_DECREF(col);
return NULL;
}
}
}
// Free temporary columns
Py_DECREF(col);
// Note that we don't change the refcount of the output matrix here. Output
// (re)allocation and refcounting is done in BaseGpuCorr3dMM.c_code_helper();
// in here output is just aliased to one of bottom, weights, or top.
return output;
}