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fix kernel launch logic #2353

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merged 2 commits into from
Apr 27, 2024
Merged

fix kernel launch logic #2353

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a97c6fe
fix kernel launch logic
xaellison Apr 26, 2024
6afb972
relax constraints for comparator
xaellison Apr 26, 2024
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14 changes: 8 additions & 6 deletions src/sorting.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -908,18 +908,20 @@ function bitonic_sort!(c; by = identity, lt = isless, rev = false, dims=1)

# compile kernels (using Int32 for indexing, if possible, yielding a 70% speedup)
I = c_len <= typemax(Int32) ? Int32 : Int

args1 = (c, I(c_len), one(I), one(I), one(I), by, lt, Val(rev), Val(dims))
kernel1 = @cuda launch=false comparator_small_kernel(args1...)

config1 = launch_configuration(kernel1.fun, shmem = threads -> bitonic_shmem(c, threads))
# blocksize for kernel1 MUST be a power of 2
threads1 = prevpow(2, config1.threads)

args2 = (c, I(c_len), one(I), one(I), by, lt, Val(rev), Val(dims))
kernel2 = @cuda launch=false comparator_kernel(args2...)
config2 = launch_configuration(kernel2.fun, shmem = threads -> bitonic_shmem(c, threads))
# blocksize for kernel2 MUST be a power of 2
threads2 = prevpow(2, config2.threads)
threads2 = config2.threads

# determines cutoff for when to use kernel1 vs kernel2
log_threads = threads2 |> log2 |> Int
log_threads = threads1 |> log2 |> Int

# These two outer loops are the same as the serial version outlined here:
# https://en.wikipedia.org/wiki/Bitonic_sorter#Example_code
Expand All @@ -940,11 +942,11 @@ function bitonic_sort!(c; by = identity, lt = isless, rev = false, dims=1)
pseudo_block_length = 1 << abs(j_final + 1 - j)
# N_pseudo_blocks = how many pseudo-blocks are in this layer of the network
N_pseudo_blocks = nextpow(2, c_len) ÷ pseudo_block_length
pseudo_blocks_per_block = threads2 ÷ pseudo_block_length
pseudo_blocks_per_block = threads1 ÷ pseudo_block_length

# grid dimensions
N_blocks = max(1, N_pseudo_blocks ÷ pseudo_blocks_per_block), other_block_dims...
block_size = pseudo_block_length, threads2 ÷ pseudo_block_length
block_size = pseudo_block_length, threads1 ÷ pseudo_block_length
kernel1(args1...; blocks=N_blocks, threads=block_size,
shmem=bitonic_shmem(c, block_size))
break
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