#section init_code_struct

if (PARAMS->choose_algo) {
  reuse_algo = 0;
  prev_algo = PARAMS->conv_algo;
  if (!PARAMS->choose_once) {
      memset(prev_img_dims, 0, sizeof(prev_img_dims));
      memset(prev_top_dims, 0, sizeof(prev_top_dims));
  }
}

#section support_code_struct

int reuse_algo;
cudnnConvolutionBwdFilterAlgo_t prev_algo;
size_t prev_img_dims[5];
size_t prev_top_dims[5];

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

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

  if (params->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;
  }

  if (PyGpuArray_DIMS(input)[0] == 0 || PyGpuArray_DIMS(km)[0] == 0 || PyGpuArray_DIMS(km)[1] == 0) {
    int err2 = GpuArray_memset(&(*kerns)->ga, 0);
    if (err2 != GA_NO_ERROR) {
        PyErr_Format(PyExc_RuntimeError,
                     "GpuDnnConv grad wrt. weights could not fill the output with zeros: %d", err2);
        return 1;
    }
    return 0;
  }

  if (c_set_tensor_for_conv(input, APPLY_SPECIFIC(input), params->num_groups) == -1)
    return 1;
  if (c_set_tensor_for_conv(output, APPLY_SPECIFIC(output), params->num_groups) == -1)
    return 1;
  if (c_set_filter(*kerns, APPLY_SPECIFIC(kerns), params->num_groups) == -1)
    return 1;

  size_t input_offset = PyGpuArray_STRIDE(input, 0) / params->num_groups;
  size_t kern_offset = PyGpuArray_STRIDE(*kerns, 0) * PyGpuArray_DIM(*kerns, 0) / params->num_groups;
  size_t output_offset = PyGpuArray_STRIDE(output, 0) / params->num_groups;

  cudnnConvolutionBwdFilterAlgo_t algo = params->conv_algo;

  cuda_enter(c->ctx);

  int expected_output_dims[5] = {0};
  err = cudnnGetConvolutionNdForwardOutputDim(desc, APPLY_SPECIFIC(input), APPLY_SPECIFIC(kerns),
                                              PyGpuArray_NDIM(input), expected_output_dims);
  if (err != CUDNN_STATUS_SUCCESS) {
    PyErr_Format(PyExc_RuntimeError, "error computing convolution output dim: %s",
                 cudnnGetErrorString(err));
    cuda_exit(c->ctx);
    return 1;
  }
  if (PyGpuArray_NDIM(input) == 4) {
    if ((PyGpuArray_DIMS(output)[0] != expected_output_dims[0]) ||
        (PyGpuArray_DIMS(output)[1] / params->num_groups != expected_output_dims[1]) ||
        (PyGpuArray_DIMS(output)[2] != expected_output_dims[2]) ||
        (PyGpuArray_DIMS(output)[3] != expected_output_dims[3])) {
      PyErr_Format(PyExc_ValueError, "impossible convolution output dim: expected %ldx%ldx%dx%ld"
                                     " but received gradient with shape %ldx%ldx%dx%ld",
                   expected_output_dims[0], expected_output_dims[1],
                   expected_output_dims[2], expected_output_dims[3],
                   PyGpuArray_DIMS(output)[0], PyGpuArray_DIMS(output)[1],
                   PyGpuArray_DIMS(output)[2], PyGpuArray_DIMS(output)[3]);
      cuda_exit(c->ctx);
      return 1;
    }
  } else if (PyGpuArray_NDIM(input) == 5) {
    if ((PyGpuArray_DIMS(output)[0] != expected_output_dims[0]) ||
        (PyGpuArray_DIMS(output)[1] != expected_output_dims[1]) ||
        (PyGpuArray_DIMS(output)[2] != expected_output_dims[2]) ||
        (PyGpuArray_DIMS(output)[3] != expected_output_dims[3]) ||
        (PyGpuArray_DIMS(output)[4] != expected_output_dims[4])) {
      PyErr_Format(PyExc_ValueError, "impossible convolution output dim: expected %ldx%ldx%ldx%ldx%ld"
                                     " but received gradient with shape %ldx%ldx%ldx%ldx%ld",
                   expected_output_dims[0], expected_output_dims[1],
                   expected_output_dims[2], expected_output_dims[3],
                   expected_output_dims[4],
                   PyGpuArray_DIMS(output)[0], PyGpuArray_DIMS(output)[1],
                   PyGpuArray_DIMS(output)[2], PyGpuArray_DIMS(output)[3],
                   PyGpuArray_DIMS(output)[4]);
      cuda_exit(c->ctx);
      return 1;
    }
  }

  if (params->choose_algo) {
    if (!params->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]);
      }
    }

    if (!reuse_algo) {
      size_t free;

      int err2 = gpucontext_property(c->ctx, GA_CTX_PROP_LARGEST_MEMBLOCK, &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;
      }

      // Guess 4Mb if the info is not available
      if (free == 0) free = 4 * 1024 * 1024;

      if (params->choose_time) {
        int count;
        cudnnConvolutionBwdFilterAlgoPerf_t choice;
        gpudata *tmpmem;

        tmpmem = gpudata_alloc(c->ctx, free, NULL, 0, NULL);
        if (tmpmem == NULL) {
          PyErr_SetString(PyExc_MemoryError, "Could not allocate working GPU memory");
          return -1;
        }

        err = cudnnFindConvolutionBackwardFilterAlgorithmEx(
          params->handle, APPLY_SPECIFIC(input), PyGpuArray_DEV_DATA(input),
          APPLY_SPECIFIC(output), PyGpuArray_DEV_DATA(output), desc,
          APPLY_SPECIFIC(kerns), PyGpuArray_DEV_DATA(*kerns),
          1, &count, &choice, *(void **)tmpmem, free);
        gpudata_release(tmpmem);

        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 {
        err = cudnnGetConvolutionBackwardFilterAlgorithm(
          params->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;
        }
      }
      prev_algo = algo;
    } else {
      algo = prev_algo;
    }

    if (params->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);
      }
    }

    #ifdef DEBUG
    char algorithm_name[128];
    if (0 != theano_enum_to_string_cudnnConvolutionBwdFilterAlgo_t(algo, algorithm_name)) {
        return 1;
    };
    // NB: This is printed only when algorithm is chosen at runtime.
    fprintf(stderr, "(using %s) ", algorithm_name);
    #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(
    params->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 = gpudata_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);

  for ( int g = 0; g < params->num_groups; g++)
  {

    err = cudnnConvolutionBackwardFilter(
      params->handle,
      alpha_p,
      APPLY_SPECIFIC(input), ((char *)PyGpuArray_DEV_DATA(input)) + input_offset * g ,
      APPLY_SPECIFIC(output), ((char *)PyGpuArray_DEV_DATA(output)) + output_offset * g,
      desc, algo, worksize == 0 ? NULL : *(void **)workspace, worksize,
      beta_p,
      APPLY_SPECIFIC(kerns), ((char *)PyGpuArray_DEV_DATA(*kerns)) + kern_offset * g);
  }

  if (worksize != 0)
    gpudata_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;
}
