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Fix sliding window alignment regression in QNN models #1938

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Merged
apsonawane merged 2 commits into from
Jan 8, 2026
Merged

Fix sliding window alignment regression in QNN models #1938

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42d64af
Fix alignment for qnn models
apsonawane Jan 7, 2026
8bd0b21
Revert the alignment logic
apsonawane Jan 8, 2026
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24 changes: 7 additions & 17 deletions src/generators.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -318,24 +318,14 @@ DeviceSpan<int32_t> Generator::AllocateInputIdsOnDevice(cpu_span<const int32_t>

auto input_ids_device = state_->params_->p_device->Allocate<int32_t>(padded_input_ids_size);
auto cpu_span = input_ids_device.CpuSpan();

// Handle padding based on alignment setting for sliding window models
if (padded_input_ids_size > input_ids.size()) {
const bool left_align = model_->config_->model.decoder.sliding_window.has_value() &&
model_->config_->model.decoder.sliding_window->alignment == "left";

if (left_align) {
// Left alignment: padding first, then data
std::fill_n(cpu_span.begin(), padded_input_ids_size - input_ids.size(), model_->config_->model.pad_token_id);
std::copy(input_ids.begin(), input_ids.end(), cpu_span.begin() + (padded_input_ids_size - input_ids.size()));
} else {
// Right alignment (default): data first, then padding
std::copy(input_ids.begin(), input_ids.end(), cpu_span.begin());
std::fill(cpu_span.begin() + input_ids.size(), cpu_span.end(), model_->config_->model.pad_token_id);
}
} else {
std::copy(input_ids.begin(), input_ids.end(), cpu_span.begin());
auto padding_begin = cpu_span.begin();
auto data_end = cpu_span.end();
if (model_->config_->model.decoder.sliding_window.has_value() && model_->config_->model.decoder.sliding_window->alignment == "left") {
padding_begin = cpu_span.begin() + input_ids.size();
data_end = padding_begin;
}
std::fill_n(padding_begin, padded_input_ids_size - input_ids.size(), model_->config_->model.pad_token_id);
std::copy_backward(input_ids.begin(), input_ids.end(), data_end);
input_ids_device.CopyCpuToDevice();
return input_ids_device;
}
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