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add fftshift and ifftshift fft helpers (#2135)

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* add fftshift and ifftshift fft helpers

* address comments

* axes have to be iterable

* fix fp error in roll + add test

---------

Co-authored-by: Aashiq Dheeraj <aashiq@aashiq-mbp-m4.local>
This commit is contained in:
Aashiq Dheeraj
2025-04-30 01:13:45 -04:00
committed by GitHub
parent 7bb063bcb3
commit bb6565ef14
9 changed files with 275 additions and 2 deletions
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58
tests/fft_tests.cpp
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@@ -308,3 +308,61 @@ TEST_CASE("test fft grads") {
.second;
CHECK_EQ(vjp_out.shape(), Shape{5, 5});
}
TEST_CASE("test fftshift and ifftshift") {
// Test 1D array with even length
auto x = arange(8);
auto y = fft::fftshift(x);
CHECK_EQ(y.shape(), x.shape());
// print y
CHECK(array_equal(y, array({4, 5, 6, 7, 0, 1, 2, 3})).item<bool>());
// Test 1D array with odd length
x = arange(7);
y = fft::fftshift(x);
CHECK_EQ(y.shape(), x.shape());
CHECK(array_equal(y, array({4, 5, 6, 0, 1, 2, 3})).item<bool>());
// Test 2D array
x = reshape(arange(16), {4, 4});
y = fft::fftshift(x);
auto expected =
array({10, 11, 8, 9, 14, 15, 12, 13, 2, 3, 0, 1, 6, 7, 4, 5}, {4, 4});
CHECK(array_equal(y, expected).item<bool>());
// Test with specific axes
y = fft::fftshift(x, {0});
expected =
array({8, 9, 10, 11, 12, 13, 14, 15, 0, 1, 2, 3, 4, 5, 6, 7}, {4, 4});
CHECK(array_equal(y, expected).item<bool>());
y = fft::fftshift(x, {1});
expected =
array({2, 3, 0, 1, 6, 7, 4, 5, 10, 11, 8, 9, 14, 15, 12, 13}, {4, 4});
CHECK(array_equal(y, expected).item<bool>());
// Test ifftshift (inverse operation)
x = arange(8);
y = fft::ifftshift(x);
CHECK_EQ(y.shape(), x.shape());
CHECK(array_equal(y, array({4, 5, 6, 7, 0, 1, 2, 3})).item<bool>());
// Test ifftshift with odd length (different from fftshift)
x = arange(7);
y = fft::ifftshift(x);
CHECK_EQ(y.shape(), x.shape());
CHECK(array_equal(y, array({3, 4, 5, 6, 0, 1, 2})).item<bool>());
// Test 2D ifftshift
x = reshape(arange(16), {4, 4});
y = fft::ifftshift(x);
expected =
array({10, 11, 8, 9, 14, 15, 12, 13, 2, 3, 0, 1, 6, 7, 4, 5}, {4, 4});
CHECK(array_equal(y, expected).item<bool>());
// Test error cases
CHECK_THROWS_AS(fft::fftshift(x, {3}), std::invalid_argument);
CHECK_THROWS_AS(fft::fftshift(x, {-5}), std::invalid_argument);
CHECK_THROWS_AS(fft::ifftshift(x, {3}), std::invalid_argument);
CHECK_THROWS_AS(fft::ifftshift(x, {-5}), std::invalid_argument);
}