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Fix gather vmap (#1563)

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* fix gather

* fix
This commit is contained in:
Awni Hannun 2024-11-05 11:29:20 -08:00 committed by GitHub
parent 26be608470
commit 54f05e7195
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2 changed files with 83 additions and 29 deletions
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67
mlx/primitives.cpp
View File

@ -1,5 +1,4 @@
// Copyright © 2023-2024 Apple Inc.
#include <algorithm>
#include <cassert>
#include <cmath>
@ -1683,48 +1682,58 @@ std::pair<std::vector<array>, std::vector<int>> Gather::vmap(
auto gather_axes = axes_;
auto slice_sizes = slice_sizes_;
auto src_vmapped = axes[0] >= 0;
auto indices_vmapped =
std::any_of(axes.begin() + 1, axes.end(), [](int a) { return a >= 0; });
auto out_ax =
*std::find_if(axes.begin(), axes.end(), [](int a) { return a >= 0; });
auto ind_vmap_ax_ptr =
std::find_if(axes.begin() + 1, axes.end(), [](int a) { return a >= 0; });
int out_ax = -1;
bool indices_vmapped = (ind_vmap_ax_ptr != axes.end());
if (indices_vmapped) {
out_ax = *ind_vmap_ax_ptr;
} else if (src_vmapped) {
out_ax = axes[0];
}
// Reorder all the index arrays so the vmap axis is in the same spot.
for (int i = 1; i < axes.size(); ++i) {
if (out_ax != axes[i] && axes[i] >= 0) {
indices[i - 1] = moveaxis(indices[i - 1], axes[i], out_ax, stream());
if (indices_vmapped) {
for (int i = 1; i < axes.size(); ++i) {
if (out_ax != axes[i] && axes[i] >= 0) {
indices[i - 1] = moveaxis(indices[i - 1], axes[i], out_ax, stream());
} else if (axes[i] < 0) {
indices[i - 1] = expand_dims(indices[i - 1], out_ax, stream());
}
}
}
int idx_dims = indices.empty() ? 0 : indices[0].ndim();
if (src_vmapped) {
int max_dims = 0;
for (auto& idx : indices) {
max_dims = std::max(static_cast<int>(idx.ndim()), max_dims);
}
auto new_ax_loc =
std::find_if(gather_axes.begin(), gather_axes.end(), [&out_ax](int a) {
return a >= out_ax;
});
for (; new_ax_loc < gather_axes.end(); new_ax_loc++) {
(*new_ax_loc)++;
for (auto& ax : gather_axes) {
if (ax >= axes[0]) {
ax++;
}
}
if (indices_vmapped) {
// Make a new index array for the vmapped dimension
auto vmap_inds = arange(0, src.shape(axes[0]), stream());
// Reshape it so it broadcasts with other index arrays
{
auto shape = std::vector<int>(idx_dims, 1);
shape[out_ax] = vmap_inds.size();
vmap_inds = reshape(vmap_inds, std::move(shape), stream());
}
// Update gather axes and slice sizes accordingly
auto shape = std::vector<int>(max_dims - out_ax, 1);
auto vmap_inds = arange(0, src.shape(out_ax), stream());
shape[0] = vmap_inds.shape(0);
vmap_inds = reshape(vmap_inds, shape, stream());
slice_sizes.insert(slice_sizes.begin() + out_ax, 1);
auto new_ax_idx = new_ax_loc - gather_axes.begin();
gather_axes.insert(new_ax_loc, out_ax);
indices.insert(indices.begin() + new_ax_idx, vmap_inds);
slice_sizes.insert(slice_sizes.begin() + axes[0], 1);
gather_axes.push_back(axes[0]);
indices.push_back(vmap_inds);
} else {
slice_sizes.insert(slice_sizes.begin() + axes[0], src.shape(axes[0]));
out_ax = max_dims + axes[0];
slice_sizes.insert(slice_sizes.begin() + out_ax, src.shape(out_ax));
out_ax += idx_dims;
}
}
return {{gather(src, indices, gather_axes, slice_sizes, stream())}, {out_ax}};
auto out = gather(src, indices, gather_axes, slice_sizes, stream());
if (src_vmapped && indices_vmapped) {
out = squeeze(out, idx_dims + axes[0], stream());
}
return {{out}, {out_ax}};
}
std::vector<array> Gather::vjp(

45
python/tests/test_vmap.py
View File

@ -370,6 +370,51 @@ class TestVmap(mlx_tests.MLXTestCase):
mx.allclose(a[:, i, :] @ invs[i], mx.eye(a.shape[0]), rtol=0, atol=1e-5)
)
def test_vmap_gather(self):
def gather(a, idx):
return a[idx]
a = mx.array([[1, 2], [3, 4]])
idx = mx.array(0)
out = mx.vmap(gather, (0, None))(a, idx)
self.assertTrue(mx.array_equal(out, mx.array([1, 3])))
out = mx.vmap(gather, (1, None))(a, idx)
self.assertTrue(mx.array_equal(out, mx.array([1, 2])))
idx = mx.array([0, 1])
out = mx.vmap(gather, (0, 0))(a, idx)
self.assertTrue(mx.array_equal(out, mx.array([1, 4])))
a = mx.ones((2, 3, 4))
idx = mx.zeros(4, mx.int32)
out = mx.vmap(gather, (2, 0))(a, idx)
self.assertEqual(out.shape, (4, 3))
f = mx.vmap(gather, (0, None))
f = mx.vmap(gather, (0, 0))
out = f(mx.ones((2, 3, 4)), mx.zeros(2, dtype=mx.int32))
self.assertEqual(out.shape, (2, 4))
def gather(a, idxa, idxb):
return a[idxa, idxb]
a = mx.ones((2, 3, 4))
idxa = mx.zeros((2, 3), mx.int32)
idxb = mx.zeros(3, mx.int32)
out = mx.vmap(gather, (0, 0, None))(a, idxa, idxb)
self.assertEqual(out.shape, (2, 3))
idxa = mx.zeros((3, 1, 2), mx.int32)
idxb = mx.zeros((2, 3, 1, 2), mx.int32)
out = mx.vmap(gather, (0, None, 0))(a, idxa, idxb)
self.assertEqual(out.shape, (2, 3, 1, 2))
idxa = mx.zeros((3, 1, 2), mx.int32)
idxb = mx.zeros((3, 1, 2, 2), mx.int32)
out = mx.vmap(gather, (0, None, 3))(a, idxa, idxb)
self.assertEqual(out.shape, (2, 3, 1, 2))
def test_vmap_scatter(self):
def scatter(a):
a[mx.array(0)] = mx.array(0.0)