#section init_code_struct

#ifdef CHOOSE_ALGO
reuse_algo = 0;
prev_algo = CONV_ALGO;
#ifndef CHOOSE_ONCE
memset(prev_img_dims, 0, sizeof(prev_img_dims));
memset(prev_top_dims, 0, sizeof(prev_top_dims));
#endif
#endif

#section support_code_struct

#ifdef CHOOSE_ALGO
int reuse_algo;
cudnnConvolutionBwdFilterAlgo_t prev_algo;
#ifndef CHOOSE_ONCE
size_t prev_img_dims[5];
size_t prev_top_dims[5];
#endif
#endif

int
APPLY_SPECIFIC(conv_gw)(PyGpuArrayObject *input, PyGpuArrayObject *output,
                        PyGpuArrayObject *km,
                        cudnnConvolutionDescriptor_t desc,
                        double alpha, double beta, PyGpuArrayObject **kerns,
                        PyGpuContextObject *c) {
  cudnnStatus_t err = CUDNN_STATUS_SUCCESS;
  float af = alpha, bf = beta;
  void *alpha_p;
  void *beta_p;

  if (PyGpuArray_DIMS(input)[1] != PyGpuArray_DIMS(km)[1]) {
    PyErr_SetString(PyExc_ValueError,
		    "GpuDnnConv images and kernel must have the same stack size");
    return 1;
  }

  if (c_set_tensorNd(input, APPLY_SPECIFIC(input)) == -1)
    return 1;
  if (c_set_tensorNd(output, APPLY_SPECIFIC(output)) == -1)
    return 1;

  switch (input->ga.typecode) {
  case GA_DOUBLE:
    alpha_p = (void *)&alpha;
    beta_p = (void *)&beta;
    break;
  case GA_FLOAT:
  case GA_HALF:
    alpha_p = (void *)&af;
    beta_p = (void *)&bf;
    break;
  default:
    PyErr_SetString(PyExc_TypeError, "Unsupported type in convolution");
    return 1;
  }

#ifdef CONV_INPLACE
  Py_XDECREF(*kerns);
  *kerns = km;
  Py_INCREF(*kerns);
#else
  if (theano_prep_output(kerns, PyGpuArray_NDIM(km), PyGpuArray_DIMS(km),
                         km->ga.typecode, GA_C_ORDER, c) != 0)
    return 1;
  if (beta != 0.0 && pygpu_move(*kerns, km))
    return 1;
#endif

  if (c_set_filter(*kerns, APPLY_SPECIFIC(kerns)) == -1)
    return 1;

  cudnnConvolutionBwdFilterAlgo_t algo = CONV_ALGO;

  cuda_enter(c->ctx);

#ifdef CHOOSE_ALGO
#ifndef CHOOSE_ONCE
  reuse_algo = 1;
  for (unsigned int i = 0; i < PyGpuArray_NDIM(input); i++) {
    reuse_algo = (reuse_algo &&
                  PyGpuArray_DIM(input, i) == prev_img_dims[i]);
    reuse_algo = (reuse_algo &&
                  PyGpuArray_DIM(output, i) == prev_top_dims[i]);
  }
#endif

  if (!reuse_algo) {
#ifdef CHOOSE_TIME
    int count;
    cudnnConvolutionBwdFilterAlgoPerf_t choice;

    err = cudnnFindConvolutionBackwardFilterAlgorithm(
      APPLY_SPECIFIC(_handle), APPLY_SPECIFIC(input), APPLY_SPECIFIC(output), desc,
      APPLY_SPECIFIC(kerns), 1, &count, &choice);

    if (err != CUDNN_STATUS_SUCCESS) {
      PyErr_Format(PyExc_RuntimeError,
                   "error selecting convolution algo: %s",
                   cudnnGetErrorString(err));
      cuda_exit(c->ctx);
      return 1;
    }

    algo = choice.algo;
#else
    size_t free;
    int err2 = c->ops->property(c->ctx, NULL, NULL, GA_CTX_PROP_FREE_GMEM, &free);

    if (err2 != GA_NO_ERROR) {
      PyErr_Format(PyExc_RuntimeError, "Error when trying to find the "
                   "memory information on the GPU");
      cuda_exit(c->ctx);
      return 1;
    }

    err = cudnnGetConvolutionBackwardFilterAlgorithm(
      APPLY_SPECIFIC(_handle), APPLY_SPECIFIC(input), APPLY_SPECIFIC(output),
      desc, APPLY_SPECIFIC(kerns),
      CUDNN_CONVOLUTION_BWD_FILTER_SPECIFY_WORKSPACE_LIMIT, free, &algo);
    if (err != CUDNN_STATUS_SUCCESS) {
      PyErr_Format(PyExc_RuntimeError,
                   "error selecting convolution algo: %s",
                   cudnnGetErrorString(err));
      cuda_exit(c->ctx);
      return 1;
    }
#endif
    prev_algo = algo;
  } else {
    algo = prev_algo;
  }

#ifdef CHOOSE_ONCE
  reuse_algo = 1;
#else
  for (unsigned int i = 0; i < PyGpuArray_NDIM(input); i++) {
    prev_img_dims[i] = PyGpuArray_DIM(input, i);
    prev_top_dims[i] = PyGpuArray_DIM(output, i);
  }
#endif

#endif

  // The FFT implementation does not support strides, 1x1 filters or inputs
  // with a spatial dimension larger than 1024.
  // If the chosen implementation is FFT, validate that it can
  // be used on the current data and default to a safe implementation if it
  // can't.
  // The following code is 2d-specific but it is fine as FFT and tiled-FFT are
  // defined only for 2d filters
  if (algo == CUDNN_CONVOLUTION_BWD_FILTER_ALGO_FFT &&
      PyGpuArray_NDIM(input) == 4) {
    // Extract the properties of the convolution descriptor
    int nd;
    int pad[2];
    int stride[2];
    int upscale[2];
    cudnnConvolutionMode_t mode;
    cudnnDataType_t data_type;
    err = cudnnGetConvolutionNdDescriptor(desc, 2, &nd, pad, stride,
                                             upscale, &mode, &data_type);
    if (err != CUDNN_STATUS_SUCCESS) {
      PyErr_Format(PyExc_RuntimeError,
                   "error getting convolution properties: %s",
                   cudnnGetErrorString(err));
      cuda_exit(c->ctx);
      return 1;
    }

    if (stride[0] != 1 || stride[1] != 1 ||
        PyGpuArray_DIM(input, 2) > 1024 || PyGpuArray_DIM(input, 3) > 1024 ||
        (PyGpuArray_DIM(*kerns, 2) == 1 && PyGpuArray_DIM(*kerns, 3) == 1)) {
      algo = CUDNN_CONVOLUTION_BWD_FILTER_ALGO_0;
    }
  }

  size_t worksize;
  gpudata *workspace;

  err = cudnnGetConvolutionBackwardFilterWorkspaceSize(
    APPLY_SPECIFIC(_handle), APPLY_SPECIFIC(input), APPLY_SPECIFIC(output), desc,
    APPLY_SPECIFIC(kerns), algo, &worksize);

  if (err != CUDNN_STATUS_SUCCESS) {
    PyErr_Format(PyExc_RuntimeError, "error getting worksize: %s",
                 cudnnGetErrorString(err));
      cuda_exit(c->ctx);
    return 1;
  }

  if (worksize != 0) {
    workspace = c->ops->buffer_alloc(c->ctx, worksize, NULL, 0, NULL);
    if (workspace == NULL) {
      PyErr_SetString(PyExc_RuntimeError, "Could not allocate working memory");
      cuda_exit(c->ctx);
      return 1;
    }
  }

  cuda_wait(input->ga.data, GPUARRAY_CUDA_WAIT_READ);
  cuda_wait(output->ga.data, GPUARRAY_CUDA_WAIT_READ);
  cuda_wait((*kerns)->ga.data, GPUARRAY_CUDA_WAIT_WRITE);

  err = cudnnConvolutionBackwardFilter(
    APPLY_SPECIFIC(_handle),
    alpha_p,
    APPLY_SPECIFIC(input), PyGpuArray_DEV_DATA(input),
    APPLY_SPECIFIC(output), PyGpuArray_DEV_DATA(output),
    desc, algo, worksize == 0 ? NULL : *(void **)workspace, worksize,
    beta_p,
    APPLY_SPECIFIC(kerns), PyGpuArray_DEV_DATA(*kerns));

  if (worksize != 0)
    c->ops->buffer_release(workspace);

  cuda_record(input->ga.data, GPUARRAY_CUDA_WAIT_READ);
  cuda_record(output->ga.data, GPUARRAY_CUDA_WAIT_READ);
  cuda_record((*kerns)->ga.data, GPUARRAY_CUDA_WAIT_WRITE);

  cuda_exit(c->ctx);

  if (err != CUDNN_STATUS_SUCCESS) {
    PyErr_Format(PyExc_RuntimeError, "error doing operation: %s",
                 cudnnGetErrorString(err));
    return 1;
  }
  return 0;
}
