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scatter axis + gather axis primitives #1813

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Feb 1, 2025
Merged

scatter axis + gather axis primitives #1813

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6fb1fff
scatter axis + gather axis primitives
awni Jan 31, 2025
aadf66e
add transforms
awni Jan 31, 2025
199baf0
comment
awni Jan 31, 2025
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321 changes: 301 additions & 20 deletions mlx/backend/common/indexing.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -16,11 +16,6 @@ inline size_t offset_neg_idx(IdxT idx, size_t size) {
return (idx < 0) ? idx + size : idx;
}

template <>
inline size_t offset_neg_idx(bool idx, size_t) {
return idx;
}

template <>
inline size_t offset_neg_idx(uint32_t idx, size_t) {
return idx;
Expand Down Expand Up @@ -169,14 +164,11 @@ void Gather::eval_cpu(const std::vector<array>& inputs, array& out) {
std::vector<array> inds(inputs.begin() + 1, inputs.end());

if (inds.empty()) {
dispatch_gather<bool>(src, inds, out, axes_, slice_sizes_);
dispatch_gather<uint8_t>(src, inds, out, axes_, slice_sizes_);
return;
}

switch (inds[0].dtype()) {
case bool_:
dispatch_gather<bool>(src, inds, out, axes_, slice_sizes_);
break;
case uint8:
dispatch_gather<uint8_t>(src, inds, out, axes_, slice_sizes_);
break;
Expand All @@ -201,12 +193,142 @@ void Gather::eval_cpu(const std::vector<array>& inputs, array& out) {
case int64:
dispatch_gather<int64_t>(src, inds, out, axes_, slice_sizes_);
break;
default:
throw std::runtime_error(
"[Gather::eval_cpu] Cannot gather with indices type.");
break;
}
}
template <typename T, typename IdxT>
void gather_axis(
const array& src,
const array& ind,
array& out,
const int axis) {
auto strides = ind.strides();
strides.erase(strides.begin() + axis);
auto shape = ind.shape();
shape.erase(shape.begin() + axis);
ContiguousIterator ind_it(shape, strides, src.ndim() - 1);

strides = src.strides();
strides.erase(strides.begin() + axis);
ContiguousIterator src_it(shape, strides, src.ndim() - 1);

auto ind_ptr = ind.data<IdxT>();
auto src_ptr = src.data<T>();
auto dst_ptr = out.data<T>();
auto ind_ax_stride = ind.strides(axis);
auto src_ax_stride = src.strides(axis);
auto dst_ax_stride = out.strides(axis);
auto ind_ax_size = ind.shape(axis);
auto src_ax_size = src.shape(axis);

size_t size_pre = 1;
size_t size_post = 1;
for (int i = 0; i < axis; ++i) {
size_pre *= ind.shape(i);
}
for (int i = axis + 1; i < ind.ndim(); ++i) {
size_post *= ind.shape(i);
}
size_t stride_pre = size_post * ind_ax_size;
for (size_t i = 0; i < size_pre; i++) {
for (size_t k = 0; k < size_post; k++) {
for (int j = 0; j < ind_ax_size; ++j) {
auto ind_val = offset_neg_idx(
ind_ptr[ind_it.loc + j * ind_ax_stride], src_ax_size);
dst_ptr[k + j * dst_ax_stride] =
src_ptr[src_it.loc + ind_val * src_ax_stride];
}
ind_it.step();
src_it.step();
}
dst_ptr += stride_pre;
}
}

template <typename IdxT>
void dispatch_gather_axis(
const array& src,
const array& inds,
array& out,
const int axis) {
switch (out.dtype()) {
case bool_:
gather_axis<bool, IdxT>(src, inds, out, axis);
break;
case uint8:
gather_axis<uint8_t, IdxT>(src, inds, out, axis);
break;
case uint16:
gather_axis<uint16_t, IdxT>(src, inds, out, axis);
break;
case uint32:
gather_axis<uint32_t, IdxT>(src, inds, out, axis);
break;
case uint64:
gather_axis<uint64_t, IdxT>(src, inds, out, axis);
break;
case int8:
gather_axis<int8_t, IdxT>(src, inds, out, axis);
break;
case int16:
gather_axis<int16_t, IdxT>(src, inds, out, axis);
break;
case int32:
gather_axis<int32_t, IdxT>(src, inds, out, axis);
break;
case int64:
gather_axis<int64_t, IdxT>(src, inds, out, axis);
break;
case float16:
gather_axis<float16_t, IdxT>(src, inds, out, axis);
break;
case float32:
gather_axis<float, IdxT>(src, inds, out, axis);
break;
case bfloat16:
gather_axis<bfloat16_t, IdxT>(src, inds, out, axis);
break;
case complex64:
gather_axis<complex64_t, IdxT>(src, inds, out, axis);
break;
}
}

void GatherAxis::eval_cpu(const std::vector<array>& inputs, array& out) {
out.set_data(allocator::malloc_or_wait(out.nbytes()));
auto& src = inputs[0];
auto& inds = inputs[1];
switch (inds.dtype()) {
case uint8:
dispatch_gather_axis<uint8_t>(src, inds, out, axis_);
break;
case uint16:
dispatch_gather_axis<uint16_t>(src, inds, out, axis_);
break;
case uint32:
dispatch_gather_axis<uint32_t>(src, inds, out, axis_);
break;
case uint64:
dispatch_gather_axis<uint64_t>(src, inds, out, axis_);
break;
case int8:
dispatch_gather_axis<int8_t>(src, inds, out, axis_);
break;
case int16:
dispatch_gather_axis<int16_t>(src, inds, out, axis_);
break;
case int32:
dispatch_gather_axis<int32_t>(src, inds, out, axis_);
break;
case int64:
dispatch_gather_axis<int64_t>(src, inds, out, axis_);
break;
default:
throw std::runtime_error(
"[Gather::eval] Cannot gather with floating point indices.");
"[GatherAxis::eval_cpu] Cannot gather with indices type.");
break;
}
}
Expand Down Expand Up @@ -296,14 +418,11 @@ void dispatch_scatter(
const std::vector<int>& axes,
Scatter::ReduceType rtype) {
if (inds.empty()) {
dispatch_scatter_inds<InT, bool>(out, inds, updates, axes, rtype);
dispatch_scatter_inds<InT, uint8_t>(out, inds, updates, axes, rtype);
return;
}

switch (inds[0].dtype()) {
case bool_:
dispatch_scatter_inds<InT, bool>(out, inds, updates, axes, rtype);
break;
case uint8:
dispatch_scatter_inds<InT, uint8_t>(out, inds, updates, axes, rtype);
break;
Expand All @@ -328,12 +447,9 @@ void dispatch_scatter(
case int64:
dispatch_scatter_inds<InT, int64_t>(out, inds, updates, axes, rtype);
break;
case float16:
case float32:
case bfloat16:
case complex64:
default:
throw std::runtime_error(
"[Scatter::eval_cpu] Cannot scatter with floating point indices.");
"[Scatter::eval_cpu] Cannot scatter with indices type.");
}
}

Expand All @@ -345,7 +461,9 @@ void Scatter::eval_cpu(const std::vector<array>& inputs, array& out) {
auto& updates = inputs.back();

// Copy src into out (copy allocates memory for out)
copy(src, out, CopyType::General);
auto ctype =
src.flags().row_contiguous ? CopyType::Vector : CopyType::General;
copy(src, out, ctype);

switch (src.dtype()) {
case bool_:
Expand Down Expand Up @@ -390,4 +508,167 @@ void Scatter::eval_cpu(const std::vector<array>& inputs, array& out) {
}
}

template <typename T, typename IdxT, typename OpT>
void scatter_axis(
array& out,
const array idx,
const array& upd,
int axis,
const OpT& op) {
auto strides = idx.strides();
strides.erase(strides.begin() + axis);
auto shape = idx.shape();
shape.erase(shape.begin() + axis);
ContiguousIterator idx_it(shape, strides, upd.ndim() - 1);

strides = upd.strides();
strides.erase(strides.begin() + axis);
ContiguousIterator upd_it(shape, strides, upd.ndim() - 1);

auto idx_ptr = idx.data<IdxT>();
auto upd_ptr = upd.data<T>();
auto dst_ptr = out.data<T>();
auto idx_ax_stride = idx.strides(axis);
auto upd_ax_stride = upd.strides(axis);
auto dst_ax_stride = out.strides(axis);
auto idx_ax_size = idx.shape(axis);
auto dst_ax_size = out.shape(axis);

size_t size_pre = 1;
size_t size_post = 1;
for (int i = 0; i < axis; ++i) {
size_pre *= idx.shape(i);
}
for (int i = axis + 1; i < idx.ndim(); ++i) {
size_post *= idx.shape(i);
}
size_t stride_pre = size_post * dst_ax_size;
for (size_t i = 0; i < size_pre; i++) {
for (size_t k = 0; k < size_post; k++) {
for (int j = 0; j < idx_ax_size; ++j) {
auto ind_val = offset_neg_idx(
idx_ptr[idx_it.loc + j * idx_ax_stride], dst_ax_size);
op(upd_ptr[upd_it.loc + j * upd_ax_stride],
dst_ptr + k + ind_val * dst_ax_stride);
}
idx_it.step();
upd_it.step();
}
dst_ptr += stride_pre;
}
}

template <typename InT, typename IdxT>
void dispatch_scatter_axis_op(
array& out,
const array& idx,
const array& updates,
int axis,
ScatterAxis::ReduceType rtype) {
switch (rtype) {
case ScatterAxis::None:
scatter_axis<InT, IdxT>(
out, idx, updates, axis, [](auto x, auto* y) { (*y) = x; });
break;
case ScatterAxis::Sum:
scatter_axis<InT, IdxT>(
out, idx, updates, axis, [](auto x, auto* y) { (*y) += x; });
break;
}
}

template <typename InT>
void dispatch_scatter_axis(
array& out,
const array& idx,
const array& updates,
int axis,
ScatterAxis::ReduceType rtype) {
switch (idx.dtype()) {
case uint8:
dispatch_scatter_axis_op<InT, uint8_t>(out, idx, updates, axis, rtype);
break;
case uint16:
dispatch_scatter_axis_op<InT, uint16_t>(out, idx, updates, axis, rtype);
break;
case uint32:
dispatch_scatter_axis_op<InT, uint32_t>(out, idx, updates, axis, rtype);
break;
case uint64:
dispatch_scatter_axis_op<InT, uint64_t>(out, idx, updates, axis, rtype);
break;
case int8:
dispatch_scatter_axis_op<InT, int8_t>(out, idx, updates, axis, rtype);
break;
case int16:
dispatch_scatter_axis_op<InT, int16_t>(out, idx, updates, axis, rtype);
break;
case int32:
dispatch_scatter_axis_op<InT, int32_t>(out, idx, updates, axis, rtype);
break;
case int64:
dispatch_scatter_axis_op<InT, int64_t>(out, idx, updates, axis, rtype);
break;
default:
throw std::runtime_error(
"[ScatterAxis::eval_cpu] Cannot scatter with indices type.");
}
}

void ScatterAxis::eval_cpu(const std::vector<array>& inputs, array& out) {
assert(inputs.size() >= 2);

auto& src = inputs[0];
auto& idx = inputs[1];
auto& updates = inputs[2];

// Copy src into out (copy allocates memory for out)
auto ctype =
src.flags().row_contiguous ? CopyType::Vector : CopyType::General;
copy(src, out, ctype);

switch (src.dtype()) {
case bool_:
dispatch_scatter_axis<bool>(out, idx, updates, axis_, reduce_type_);
break;
case uint8:
dispatch_scatter_axis<uint8_t>(out, idx, updates, axis_, reduce_type_);
break;
case uint16:
dispatch_scatter_axis<uint16_t>(out, idx, updates, axis_, reduce_type_);
break;
case uint32:
dispatch_scatter_axis<uint32_t>(out, idx, updates, axis_, reduce_type_);
break;
case uint64:
dispatch_scatter_axis<uint64_t>(out, idx, updates, axis_, reduce_type_);
break;
case int8:
dispatch_scatter_axis<int8_t>(out, idx, updates, axis_, reduce_type_);
break;
case int16:
dispatch_scatter_axis<int16_t>(out, idx, updates, axis_, reduce_type_);
break;
case int32:
dispatch_scatter_axis<int32_t>(out, idx, updates, axis_, reduce_type_);
break;
case int64:
dispatch_scatter_axis<int64_t>(out, idx, updates, axis_, reduce_type_);
break;
case float16:
dispatch_scatter_axis<float16_t>(out, idx, updates, axis_, reduce_type_);
break;
case float32:
dispatch_scatter_axis<float>(out, idx, updates, axis_, reduce_type_);
break;
case bfloat16:
dispatch_scatter_axis<bfloat16_t>(out, idx, updates, axis_, reduce_type_);
break;
case complex64:
dispatch_scatter_axis<complex64_t>(
out, idx, updates, axis_, reduce_type_);
break;
}
}

} // namespace mlx::core
2 changes: 2 additions & 0 deletions mlx/backend/metal/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,8 @@ make_jit_source(ternary_ops)
make_jit_source(reduce_utils kernels/atomic.h kernels/reduction/ops.h)
make_jit_source(scatter kernels/indexing.h)
make_jit_source(gather kernels/indexing.h)
make_jit_source(gather_axis)
make_jit_source(scatter_axis)
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❤️

make_jit_source(hadamard)

if(MLX_METAL_JIT)
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