Create a plan's extra workers lazily, on the first threaded execution - #10
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pankgeorg wants to merge 20 commits into
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Create a plan's extra workers lazily, on the first threaded execution#10pankgeorg wants to merge 20 commits into
pankgeorg wants to merge 20 commits into
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W butterflies per iteration on SIMD.jl vectors (2 for ComplexF64, 4 for ComplexF32); the twiddle table keeps its compact layout and the triplets are rearranged in registers. Falls back to the scalar loop for strided or non-contiguous output and for other element types.
Above 2^18 elements the depth-first recursion reads each leaf at a stride that uses one element per cache line. Compute the 4096-point sub-transforms first, in input order, gathering one cache line of pencils at a time into a plan-owned buffer, then run the remaining butterfly passes level by level. Same operations, identical output; 2^20 43 -> 21 ms, 2^22 188 -> 101 ms (ComplexF64, Neoverse-N1, with the SIMD pass).
Symmetric odd-length DFT (cosine and sine sums over x_j ± x_{N-j}) with
folded constants, (N-1)^2 real multiplications instead of 4(N-1)^2 from a
twiddle table. Real input is accepted. Composite sizes with factors 5/7:
1000 35 -> 19 us, 46305 3.3 -> 1.9 ms, 10^6 100 -> 68 ms (ComplexF64).
Same structure as the radix-3 kernel, with the 5-/7-point codelets as in-place butterflies; replaces the composite step + O(n^2) leaves for 5^k and 7^k (Float32/Float64). 125-point 1.8 -> 1.2 us, 1000 19 -> 14 us, 10^6 68 -> 55 ms (ComplexF64).
…of two), test for 2^18-2^21 N/B must be a power of 4; with a fixed B = 4096 that failed for odd log2 N (e.g. the 2^19 complex transform inside a 2^20 rfft) and the digit reversal wrote out of bounds.
…py-based packing The even-length real transform's post-processing (and the backward pre-processing) used a per-call twiddle recurrence; the twiddles now live in the workers (Float32 accuracy at 2^20: 8e-6 -> 2.5e-7) and the loops run W values per iteration on SIMD vectors; the real<->complex pair packing is a copy. rfft 16384: 142 -> 131 us (Float64), 136 -> 118 us (Float32).
# Conflicts: # src/FFTA.jl
…56-point block The sibling leaves are computed together, one leaf per complex lane of a SIMD vector (2 for Float64, 4 for Float32), with the twiddle products written to round exactly as the scalar codelets. ComplexF64 2^14 197 -> 168 us (FFTW ESTIMATE 177), ComplexF32 2^14 146 -> 114 us.
Plans with several workers run a 1D transform of >= 2^18 points (and the half-size transform of an even-length real one) as independent sub-transforms on the workers' gather buffers, then butterfly passes split by block or by butterfly range (multiples of 64); same operations, output identical to the serial path. 16 workers, Neoverse-N1: ComplexF64 2^20 20.1 -> 1.87 ms (FFTW MEASURE 1.75 ms), 2^22 105 -> 10.2 ms (9.4 ms), rfft Float64 2^20 11.5 -> 3.2 ms (2.7 ms).
WorkerPool: the first worker is built with the plan, the others are cloned under a lock when an execution is actually split over threads. One-shot calls (fft(x), which plan with num_threads = Threads.nthreads()) no longer pay for workers they never use: fft of 2^17 one-shot at 16 threads 3.5 -> 2.8 ms. Results and the threaded paths are unchanged.
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Stacked on
integration/experiments(all previous branches).WorkerPool: the first worker is built with the plan, the others are cloned under a lock when an execution is actually split over threads; one-shot calls (fft(x), which plan withnum_threads = Threads.nthreads()) no longer pay for workers they never use. Results and the threaded paths are unchanged (p.workers[i]still works and completes the pool).16 threads, Neoverse-N1: one-shot
fftof 2^17 3.5 → 2.8 ms (same as with 1 worker); DSP.jlhilbert2^17 9.5 → 6.1 ms,conv2^16⋆2^12 6.3 → 4.1 ms,periodogram2^16 1.58 → 1.05 ms — the one-shot routines back to their 1-thread times (benchmark/compare3/aarch64/final/DSP_WORKLOADS.mdonbench/compare3).Tested: full suite green on 4 threads (11 061 tests).