mlx/mlx/backend/cpu/fft.cpp
2025-03-20 16:48:43 -07:00

121 lines
3.5 KiB
C++

// Copyright © 2023 Apple Inc.
#include <numeric>
#include "mlx/3rdparty/pocketfft.h"
#include "mlx/allocator.h"
#include "mlx/backend/cpu/encoder.h"
#include "mlx/primitives.h"
namespace mlx::core {
void FFT::eval_cpu(const std::vector<array>& inputs, array& out) {
auto& in = inputs[0];
std::vector<std::ptrdiff_t> strides_in(
in.strides().begin(), in.strides().end());
for (auto& s : strides_in) {
s *= in.itemsize();
}
std::vector<std::ptrdiff_t> strides_out(
out.strides().begin(), out.strides().end());
for (auto& s : strides_out) {
s *= out.itemsize();
}
out.set_data(allocator::malloc(out.nbytes()));
std::vector<size_t> shape;
if (out.dtype() == float32) {
shape.insert(shape.end(), out.shape().begin(), out.shape().end());
} else {
shape.insert(shape.end(), in.shape().begin(), in.shape().end());
}
float scale = 1.0f;
if (inverse_) {
size_t nelem = std::accumulate(
axes_.begin(), axes_.end(), 1, [&shape](auto x, auto y) {
return x * shape[y];
});
scale /= nelem;
}
auto& encoder = cpu::get_command_encoder(stream());
encoder.set_input_array(in);
encoder.set_output_array(out);
if (in.dtype() == complex64 && out.dtype() == complex64) {
auto in_ptr =
reinterpret_cast<const std::complex<float>*>(in.data<complex64_t>());
auto out_ptr =
reinterpret_cast<std::complex<float>*>(out.data<complex64_t>());
encoder.dispatch([shape = std::move(shape),
strides_in = std::move(strides_in),
strides_out = std::move(strides_out),
axes = axes_,
inverse = inverse_,
in_ptr,
out_ptr,
scale]() {
pocketfft::c2c(
shape,
strides_in,
strides_out,
axes,
!inverse,
in_ptr,
out_ptr,
scale);
});
} else if (in.dtype() == float32 && out.dtype() == complex64) {
auto in_ptr = in.data<float>();
auto out_ptr =
reinterpret_cast<std::complex<float>*>(out.data<complex64_t>());
encoder.dispatch([shape = std::move(shape),
strides_in = std::move(strides_in),
strides_out = std::move(strides_out),
axes = axes_,
inverse = inverse_,
in_ptr,
out_ptr,
scale]() {
pocketfft::r2c(
shape,
strides_in,
strides_out,
axes,
!inverse,
in_ptr,
out_ptr,
scale);
});
} else if (in.dtype() == complex64 && out.dtype() == float32) {
auto in_ptr =
reinterpret_cast<const std::complex<float>*>(in.data<complex64_t>());
auto out_ptr = out.data<float>();
encoder.dispatch([shape = std::move(shape),
strides_in = std::move(strides_in),
strides_out = std::move(strides_out),
axes = axes_,
inverse = inverse_,
in_ptr,
out_ptr,
scale]() {
pocketfft::c2r(
shape,
strides_in,
strides_out,
axes,
!inverse,
in_ptr,
out_ptr,
scale);
});
} else {
throw std::runtime_error(
"[FFT] Received unexpected input and output type combination.");
}
}
} // namespace mlx::core