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Use std::optional for mask_arr arg #2763

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Merged
zcbenz merged 1 commit into from
Nov 17, 2025
Merged

Use std::optional for mask_arr arg #2763

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35 changes: 12 additions & 23 deletions mlx/fast.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -578,7 +578,7 @@ array scaled_dot_product_attention(
const array& values,
const float scale,
const std::string& mask_mode /* = "" */,
const std::vector<array>& mask_arrs /* = {} */,
std::optional<array> mask_arr /* = {} */,
const std::optional<array>& sinks /* = {} */,
StreamOrDevice s /* = {}*/) {
for (const auto& tensor : {queries, keys, values}) {
Expand Down Expand Up @@ -606,32 +606,22 @@ array scaled_dot_product_attention(
has_mask = true;
do_causal = true;

if (!mask_arrs.empty()) {
if (mask_arr) {
std::ostringstream msg;
msg << "[scaled_dot_product_attention] Invalid mask_arrs for mask_mode "
<< "'casusal'. No array masks supported.";
msg << "[scaled_dot_product_attention] Invalid mask_arr for mask_mode "
<< "'casusal'. No array mask should be passed.";
throw std::invalid_argument(msg.str());
}
}

if (mask_mode == "array" || (mask_mode == "" && !mask_arrs.empty())) {
if (mask_arrs.size() != 1) {
std::ostringstream msg;
msg << "[scaled_dot_product_attention] Invalid mask_arrs for mask_mode "
<< "'" << mask_mode << "'. Only 1 mask array is supported, got "
<< mask_arrs.size() << "arrays.";
throw std::invalid_argument(msg.str());
}

} else if (mask_arr) {
has_mask = true;
has_arr_mask = true;
has_bool_mask = mask_arrs[0].dtype() == bool_;
has_bool_mask = mask_arr->dtype() == bool_;
}

if (has_arr_mask && (mask_arrs[0]).ndim() > 4) {
if (has_arr_mask && mask_arr->ndim() > 4) {
std::ostringstream msg;
msg << "[scaled_dot_product_attention] the mask with shape "
<< mask_arrs[0].shape() << " expected to have at most rank 4.";
<< mask_arr->shape() << " expected to have at most rank 4.";
throw std::invalid_argument(msg.str());
}

Expand Down Expand Up @@ -764,20 +754,19 @@ array scaled_dot_product_attention(
std::vector<array> inputs = {q, k, v};
if (has_arr_mask) {
// Check type
auto mask_arr = mask_arrs[0];
has_bool_mask = mask_arr.dtype() == bool_;
if (promote_types(mask_arr.dtype(), final_type) != final_type) {
has_bool_mask = mask_arr->dtype() == bool_;
if (promote_types(mask_arr->dtype(), final_type) != final_type) {
std::ostringstream msg;
msg << "[scaled_dot_product_attention] Mask type must promote to output type "
<< final_type << ".";
throw std::invalid_argument(msg.str());
} else if (!has_bool_mask) {
mask_arr = astype(mask_arr, final_type, stream);
mask_arr = astype(*mask_arr, final_type, stream);
}
// Broadcast mask
auto mask_shape = queries.shape();
mask_shape.back() = keys.shape(-2);
inputs.push_back(broadcast_to(mask_arr, mask_shape, stream));
inputs.push_back(broadcast_to(*mask_arr, mask_shape, stream));
}
if (has_sinks) {
if (promote_types(sinks->dtype(), final_type) != final_type) {
Expand Down
2 changes: 1 addition & 1 deletion mlx/fast.h
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Original file line number Diff line number Diff line change
Expand Up @@ -49,7 +49,7 @@ array scaled_dot_product_attention(
const array& values,
const float scale,
const std::string& mask_mode = "",
const std::vector<array>& mask_arrs = {},
std::optional<array> mask_arr = {},
const std::optional<array>& sinks = {},
StreamOrDevice s = {});

Expand Down
4 changes: 2 additions & 2 deletions python/src/fast.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -213,11 +213,11 @@ void init_fast(nb::module_& parent_module) {
throw std::invalid_argument(msg.str());
}
return mx::fast::scaled_dot_product_attention(
queries, keys, values, scale, mask_str, {}, sinks, s);
queries, keys, values, scale, mask_str, std::nullopt, sinks, s);
} else {
auto mask_arr = std::get<mx::array>(mask);
return mx::fast::scaled_dot_product_attention(
queries, keys, values, scale, "", {mask_arr}, sinks, s);
queries, keys, values, scale, "", mask_arr, sinks, s);
}

} else {
Expand Down