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/* SPDX-License-Identifier: Apache-2.0
* Copyright 2021-2022 Blender Foundation */
#pragma once
CCL_NAMESPACE_BEGIN
/* Given an array of states, build an array of indices for which the states
* are active.
*
* Shared memory requirement is `sizeof(int) * (number_of_warps + 1)`. */
#include "util/atomic.h"
#ifdef __HIP__
# define GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE 1024
#else
# define GPU_PARALLEL_ACTIVE_INDEX_DEFAULT_BLOCK_SIZE 512
#endif
#ifdef __KERNEL_METAL__
struct ActiveIndexContext {
ActiveIndexContext(int _thread_index,
int _global_index,
int _threadgroup_size,
int _simdgroup_size,
int _simd_lane_index,
int _simd_group_index,
int _num_simd_groups,
threadgroup int *_simdgroup_offset)
: thread_index(_thread_index),
global_index(_global_index),
blocksize(_threadgroup_size),
ccl_gpu_warp_size(_simdgroup_size),
thread_warp(_simd_lane_index),
warp_index(_simd_group_index),
num_warps(_num_simd_groups),
warp_offset(_simdgroup_offset)
{
}
const int thread_index, global_index, blocksize, ccl_gpu_warp_size, thread_warp, warp_index,
num_warps;
threadgroup int *warp_offset;
template<uint blocksizeDummy, typename IsActiveOp>
void active_index_array(const uint num_states,
ccl_global int *indices,
ccl_global int *num_indices,
IsActiveOp is_active_op)
{
const uint state_index = global_index;
#else
template<uint blocksize, typename IsActiveOp>
__device__ void gpu_parallel_active_index_array(const uint num_states,
ccl_global int *indices,
ccl_global int *num_indices,
IsActiveOp is_active_op)
{
extern ccl_gpu_shared int warp_offset[];
const uint thread_index = ccl_gpu_thread_idx_x;
const uint thread_warp = thread_index % ccl_gpu_warp_size;
const uint warp_index = thread_index / ccl_gpu_warp_size;
const uint num_warps = blocksize / ccl_gpu_warp_size;
const uint state_index = ccl_gpu_block_idx_x * blocksize + thread_index;
#endif
/* Test if state corresponding to this thread is active. */
const uint is_active = (state_index < num_states) ? is_active_op(state_index) : 0;
/* For each thread within a warp compute how many other active states precede it. */
const uint thread_offset = popcount(ccl_gpu_ballot(is_active) &
ccl_gpu_thread_mask(thread_warp));
/* Last thread in warp stores number of active states for each warp. */
if (thread_warp == ccl_gpu_warp_size - 1) {
warp_offset[warp_index] = thread_offset + is_active;
}
ccl_gpu_syncthreads();
/* Last thread in block converts per-warp sizes to offsets, increments global size of
* index array and gets offset to write to. */
if (thread_index == blocksize - 1) {
/* TODO: parallelize this. */
int offset = 0;
for (int i = 0; i < num_warps; i++) {
int num_active = warp_offset[i];
warp_offset[i] = offset;
offset += num_active;
}
const uint block_num_active = warp_offset[warp_index] + thread_offset + is_active;
warp_offset[num_warps] = atomic_fetch_and_add_uint32(num_indices, block_num_active);
}
ccl_gpu_syncthreads();
/* Write to index array. */
if (is_active) {
const uint block_offset = warp_offset[num_warps];
indices[block_offset + warp_offset[warp_index] + thread_offset] = state_index;
}
}
#ifdef __KERNEL_METAL__
}; /* end class ActiveIndexContext */
/* inject the required thread params into a struct, and redirect to its templated member function
*/
# define gpu_parallel_active_index_array \
ActiveIndexContext(metal_local_id, \
metal_global_id, \
metal_local_size, \
simdgroup_size, \
simd_lane_index, \
simd_group_index, \
num_simd_groups, \
simdgroup_offset) \
.active_index_array
#endif
CCL_NAMESPACE_END
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