add complex.hlsl #592
add complex.hlsl #592
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[CI]: Can one of the admins verify this patch? |
| // Fast Fourier Transform | ||
| template<typename T, uint32_t N> | ||
| void fft_radix2(complex::complex_t<T> data[N], bool is_inverse) |
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make the is_inverse a template parameter
assert(N<gl_SubgroupSize)
btw the data need not be data[N], each invocation comes with its own register value and you can cooperatively exchange via the use of subgroupShuffleXor (add it to https://github.com/Devsh-Graphics-Programming/Nabla/blob/master/include/nbl/builtin/hlsl/glsl_compat/subgroup_shuffle.hlsl please).
I mean the original GLSL code is here
https://github.com/Devsh-Graphics-Programming/Nabla/blob/master/include/nbl/builtin/glsl/subgroup/fft.glsl
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I see a certain ladder of features, and each should have their own branch (so I can merge in order without having all comments addressed):
They can branch off each other. P.S. Let me know if you need "runtime" transcendental/special functions for |
Missing compound operators and template specializations for integer types. Arithmetic logic is off, different from the STL
| // Cooley-Tukey | ||
| assign_mul_complex<T> mul_assign; | ||
| assign_div_complex<T> div_assign; | ||
| for (uint32_t stride = 2; stride <= N; stride *= 2) |
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I'd do a loop from stride=1 to stride=N/2 instead of 2->N because that's the actual stride between your butterfly elements, what you have right now is a width
| { | ||
| namespace subgroup | ||
| { | ||
| // TODO: specialize subgorupShuffleXor to different Scalar types. As of right now this would only support 1-wide scalars (no vectors) |
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thats fine, lets do 1 channel at a time
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| template<typename Scalar, uint32_t SubgroupSize, bool inverse> | ||
| void FFT(NBL_REF_ARG(complex_t<Scalar>) lo, NBL_REF_ARG(complex_t<Scalar>) hi) { |
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you need to document with comments what lo and hi are
| const uint32_t doubleSubgroupSize = SubgroupSize << 1; | ||
| // special first iteration | ||
| if (! inverse) | ||
| fft::DIX<Scalar, inverse>::radix2(fft::twiddle<Scalar, inverse>(glsl::gl_SubgroupID(), doubleSubgroupSize), lo, hi); |
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using DIX<Scalar,inverse> when you're already inside an if (inverse) or if (!inverse) makes the code super unreadable, I'd use DIT or DIF directly
| FFT_loop<Scalar, inverse>(stride, lo, hi); | ||
| // Decimation in Frequency | ||
| else | ||
| for (uint32_t stride = SubgroupSize >> 1; stride > 0; stride >>= 1) | ||
| FFT_loop<Scalar, inverse>(stride, lo, hi); |
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also substitute inverse if you already know the value
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Start drafting complex.hlsl