/*
 * Copyright 2011-2016 Blender Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "device/device_split_kernel.h"

#include "kernel/kernel_types.h"
#include "kernel/split/kernel_split_data_types.h"

#include "util/util_logging.h"
#include "util/util_time.h"

CCL_NAMESPACE_BEGIN

static const double alpha = 0.1; /* alpha for rolling average */

DeviceSplitKernel::DeviceSplitKernel(Device *device)
    : device(device),
      split_data(device, "split_data"),
      ray_state(device, "ray_state", MEM_READ_WRITE),
      queue_index(device, "queue_index"),
      use_queues_flag(device, "use_queues_flag"),
      work_pool_wgs(device, "work_pool_wgs"),
      kernel_data_initialized(false)
{
  avg_time_per_sample = 0.0;

  kernel_path_init = NULL;
  kernel_scene_intersect = NULL;
  kernel_lamp_emission = NULL;
  kernel_do_volume = NULL;
  kernel_queue_enqueue = NULL;
  kernel_indirect_background = NULL;
  kernel_shader_setup = NULL;
  kernel_shader_sort = NULL;
  kernel_shader_eval = NULL;
  kernel_holdout_emission_blurring_pathtermination_ao = NULL;
  kernel_subsurface_scatter = NULL;
  kernel_direct_lighting = NULL;
  kernel_shadow_blocked_ao = NULL;
  kernel_shadow_blocked_dl = NULL;
  kernel_enqueue_inactive = NULL;
  kernel_next_iteration_setup = NULL;
  kernel_indirect_subsurface = NULL;
  kernel_buffer_update = NULL;
}

DeviceSplitKernel::~DeviceSplitKernel()
{
  split_data.free();
  ray_state.free();
  use_queues_flag.free();
  queue_index.free();
  work_pool_wgs.free();

  delete kernel_path_init;
  delete kernel_scene_intersect;
  delete kernel_lamp_emission;
  delete kernel_do_volume;
  delete kernel_queue_enqueue;
  delete kernel_indirect_background;
  delete kernel_shader_setup;
  delete kernel_shader_sort;
  delete kernel_shader_eval;
  delete kernel_holdout_emission_blurring_pathtermination_ao;
  delete kernel_subsurface_scatter;
  delete kernel_direct_lighting;
  delete kernel_shadow_blocked_ao;
  delete kernel_shadow_blocked_dl;
  delete kernel_enqueue_inactive;
  delete kernel_next_iteration_setup;
  delete kernel_indirect_subsurface;
  delete kernel_buffer_update;
}

bool DeviceSplitKernel::load_kernels(const DeviceRequestedFeatures &requested_features)
{
#define LOAD_KERNEL(name) \
  kernel_##name = get_split_kernel_function(#name, requested_features); \
  if (!kernel_##name) { \
    device->set_error(string("Split kernel error: failed to load kernel_") + #name); \
    return false; \
  }

  LOAD_KERNEL(path_init);
  LOAD_KERNEL(scene_intersect);
  LOAD_KERNEL(lamp_emission);
  if (requested_features.use_volume) {
    LOAD_KERNEL(do_volume);
  }
  LOAD_KERNEL(queue_enqueue);
  LOAD_KERNEL(indirect_background);
  LOAD_KERNEL(shader_setup);
  LOAD_KERNEL(shader_sort);
  LOAD_KERNEL(shader_eval);
  LOAD_KERNEL(holdout_emission_blurring_pathtermination_ao);
  LOAD_KERNEL(subsurface_scatter);
  LOAD_KERNEL(direct_lighting);
  LOAD_KERNEL(shadow_blocked_ao);
  LOAD_KERNEL(shadow_blocked_dl);
  LOAD_KERNEL(enqueue_inactive);
  LOAD_KERNEL(next_iteration_setup);
  LOAD_KERNEL(indirect_subsurface);
  LOAD_KERNEL(buffer_update);

#undef LOAD_KERNEL

  /* Re-initialiaze kernel-dependent data when kernels change. */
  kernel_data_initialized = false;

  return true;
}

size_t DeviceSplitKernel::max_elements_for_max_buffer_size(device_memory &kg,
                                                           device_memory &data,
                                                           uint64_t max_buffer_size)
{
  uint64_t size_per_element = state_buffer_size(kg, data, 1024) / 1024;
  VLOG(1) << "Split state element size: " << string_human_readable_number(size_per_element)
          << " bytes. (" << string_human_readable_size(size_per_element) << ").";
  return max_buffer_size / size_per_element;
}

bool DeviceSplitKernel::path_trace(DeviceTask *task,
                                   RenderTile &tile,
                                   device_memory &kgbuffer,
                                   device_memory &kernel_data)
{
  if (device->have_error()) {
    return false;
  }

  /* Allocate all required global memory once. */
  if (!kernel_data_initialized) {
    kernel_data_initialized = true;

    /* Set local size */
    int2 lsize = split_kernel_local_size();
    local_size[0] = lsize[0];
    local_size[1] = lsize[1];

    /* Set global size */
    int2 gsize = split_kernel_global_size(kgbuffer, kernel_data, task);

    /* Make sure that set work size is a multiple of local
     * work size dimensions.
     */
    global_size[0] = round_up(gsize[0], local_size[0]);
    global_size[1] = round_up(gsize[1], local_size[1]);

    int num_global_elements = global_size[0] * global_size[1];
    assert(num_global_elements % WORK_POOL_SIZE == 0);

    /* Calculate max groups */

    /* Denotes the maximum work groups possible w.r.t. current requested tile size. */
    unsigned int work_pool_size = (device->info.type == DEVICE_CPU) ? WORK_POOL_SIZE_CPU :
                                                                      WORK_POOL_SIZE_GPU;
    unsigned int max_work_groups = num_global_elements / work_pool_size + 1;

    /* Allocate work_pool_wgs memory. */
    work_pool_wgs.alloc_to_device(max_work_groups);
    queue_index.alloc_to_device(NUM_QUEUES);
    use_queues_flag.alloc_to_device(1);
    split_data.alloc_to_device(state_buffer_size(kgbuffer, kernel_data, num_global_elements));
    ray_state.alloc(num_global_elements);
  }

  /* Number of elements in the global state buffer */
  int num_global_elements = global_size[0] * global_size[1];

#define ENQUEUE_SPLIT_KERNEL(name, global_size, local_size) \
  if (device->have_error()) { \
    return false; \
  } \
  if (!kernel_##name->enqueue( \
          KernelDimensions(global_size, local_size), kgbuffer, kernel_data)) { \
    return false; \
  }

  tile.sample = tile.start_sample;

  /* for exponential increase between tile updates */
  int time_multiplier = 1;

  while (tile.sample < tile.start_sample + tile.num_samples) {
    /* to keep track of how long it takes to run a number of samples */
    double start_time = time_dt();

    /* initial guess to start rolling average */
    const int initial_num_samples = 1;
    /* approx number of samples per second */
    int samples_per_second = (avg_time_per_sample > 0.0) ?
                                 int(double(time_multiplier) / avg_time_per_sample) + 1 :
                                 initial_num_samples;

    RenderTile subtile = tile;
    subtile.start_sample = tile.sample;
    subtile.num_samples = min(samples_per_second,
                              tile.start_sample + tile.num_samples - tile.sample);

    if (device->have_error()) {
      return false;
    }

    /* reset state memory here as global size for data_init
     * kernel might not be large enough to do in kernel
     */
    work_pool_wgs.zero_to_device();
    split_data.zero_to_device();
    ray_state.zero_to_device();

    if (!enqueue_split_kernel_data_init(KernelDimensions(global_size, local_size),
                                        subtile,
                                        num_global_elements,
                                        kgbuffer,
                                        kernel_data,
                                        split_data,
                                        ray_state,
                                        queue_index,
                                        use_queues_flag,
                                        work_pool_wgs)) {
      return false;
    }

    ENQUEUE_SPLIT_KERNEL(path_init, global_size, local_size);

    bool activeRaysAvailable = true;
    double cancel_time = DBL_MAX;

    while (activeRaysAvailable) {
      /* Do path-iteration in host [Enqueue Path-iteration kernels. */
      for (int PathIter = 0; PathIter < 16; PathIter++) {
        ENQUEUE_SPLIT_KERNEL(scene_intersect, global_size, local_size);
        ENQUEUE_SPLIT_KERNEL(lamp_emission, global_size, local_size);
        if (kernel_do_volume) {
          ENQUEUE_SPLIT_KERNEL(do_volume, global_size, local_size);
        }
        ENQUEUE_SPLIT_KERNEL(queue_enqueue, global_size, local_size);
        ENQUEUE_SPLIT_KERNEL(indirect_background, global_size, local_size);
        ENQUEUE_SPLIT_KERNEL(shader_setup, global_size, local_size);
        ENQUEUE_SPLIT_KERNEL(shader_sort, global_size, local_size);
        ENQUEUE_SPLIT_KERNEL(shader_eval, global_size, local_size);
        ENQUEUE_SPLIT_KERNEL(
            holdout_emission_blurring_pathtermination_ao, global_size, local_size);
        ENQUEUE_SPLIT_KERNEL(subsurface_scatter, global_size, local_size);
        ENQUEUE_SPLIT_KERNEL(queue_enqueue, global_size, local_size);
        ENQUEUE_SPLIT_KERNEL(direct_lighting, global_size, local_size);
        ENQUEUE_SPLIT_KERNEL(shadow_blocked_ao, global_size, local_size);
        ENQUEUE_SPLIT_KERNEL(shadow_blocked_dl, global_size, local_size);
        ENQUEUE_SPLIT_KERNEL(enqueue_inactive, global_size, local_size);
        ENQUEUE_SPLIT_KERNEL(next_iteration_setup, global_size, local_size);
        ENQUEUE_SPLIT_KERNEL(indirect_subsurface, global_size, local_size);
        ENQUEUE_SPLIT_KERNEL(queue_enqueue, global_size, local_size);
        ENQUEUE_SPLIT_KERNEL(buffer_update, global_size, local_size);

        if (task->get_cancel() && cancel_time == DBL_MAX) {
          /* Wait up to twice as many seconds for current samples to finish
           * to avoid artifacts in render result from ending too soon.
           */
          cancel_time = time_dt() + 2.0 * time_multiplier;
        }

        if (time_dt() > cancel_time) {
          return true;
        }
      }

      /* Decide if we should exit path-iteration in host. */
      ray_state.copy_from_device(0, global_size[0] * global_size[1], 1);

      activeRaysAvailable = false;

      for (int rayStateIter = 0; rayStateIter < global_size[0] * global_size[1]; ++rayStateIter) {
        if (!IS_STATE(ray_state.data(), rayStateIter, RAY_INACTIVE)) {
          if (IS_STATE(ray_state.data(), rayStateIter, RAY_INVALID)) {
            /* Something went wrong, abort to avoid looping endlessly. */
            device->set_error("Split kernel error: invalid ray state");
            return false;
          }

          /* Not all rays are RAY_INACTIVE. */
          activeRaysAvailable = true;
          break;
        }
      }

      if (time_dt() > cancel_time) {
        return true;
      }
    }

    double time_per_sample = ((time_dt() - start_time) / subtile.num_samples);

    if (avg_time_per_sample == 0.0) {
      /* start rolling average */
      avg_time_per_sample = time_per_sample;
    }
    else {
      avg_time_per_sample = alpha * time_per_sample + (1.0 - alpha) * avg_time_per_sample;
    }

#undef ENQUEUE_SPLIT_KERNEL

    tile.sample += subtile.num_samples;
    task->update_progress(&tile, tile.w * tile.h * subtile.num_samples);

    time_multiplier = min(time_multiplier << 1, 10);

    if (task->get_cancel()) {
      return true;
    }
  }

  return true;
}

CCL_NAMESPACE_END
