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Fix overflow in quantize/dequantize (#1379)

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* add 2d indices to prevent overflow

* use nthreads not out size
This commit is contained in:
Alex Barron
2024-08-30 13:32:41 -07:00
committed by GitHub
parent 1600092e92
commit da691257ec
2 changed files with 31 additions and 13 deletions
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13
mlx/backend/metal/quantized.cpp
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@@ -584,8 +584,19 @@ void fast::AffineQuantize::eval_gpu(
dequantize_ ? w.size() * uint8_per_uint32 : w.size() / per_thread;
NS::UInteger thread_group_size = kernel->maxTotalThreadsPerThreadgroup();
if (thread_group_size > nthreads) {
thread_group_size = nthreads;
}
auto group_dims = MTL::Size(thread_group_size, 1, 1);
auto grid_dims = MTL::Size(nthreads, 1, 1);
bool use_2d = nthreads > UINT_MAX;
auto grid_shape = w.shape();
if (dequantize_) {
grid_shape.back() *= uint8_per_uint32;
} else {
grid_shape.back() /= per_thread;
}
MTL::Size grid_dims = use_2d ? get_2d_grid_dims(grid_shape, w.strides())
: MTL::Size(nthreads, 1, 1);
compute_encoder.dispatchThreads(grid_dims, group_dims);
d.get_command_buffer(s.index)->addCompletedHandler(