fix loss performance (#1622)

Co-authored-by: thucpham <minhthuc.pham@systrangroup.com>

src/layers/transformer.cc

@@ -558,7 +558,7 @@ namespace ctranslate2 {
       }
 
       for (size_t i = 0; i < layer_ins.size(); ++i) {
-        auto layer_in_chunk = layer_ins[i];
+        StorageView* layer_in_chunk = &layer_ins[i];
         for (size_t l = 0; l < _layers.size(); ++l) {
           StorageView* cached_self_attn_keys = nullptr;
           StorageView* cached_self_attn_values = nullptr;
@@ -583,22 +583,22 @@ namespace ctranslate2 {
           dim_t offset = _sliding_window * i + step;
           offset = offset < 0 ? 0 : offset;
           if (i > 0) {
-            auto max_tokens = _sliding_window + layer_in_chunk.dim(1);
-            StorageView tmp_lengths = StorageView(Shape{layer_in_chunk.dim(0)}, int32_t(max_tokens), device);
+            auto max_tokens = _sliding_window + layer_in_chunk->dim(1);
+            StorageView tmp_lengths = StorageView(Shape{layer_in_chunk->dim(0)}, int32_t(max_tokens), device);
             StorageView lengths_mask = layers::MultiHeadAttention::prepare_length_mask(
               tmp_lengths,
               _num_heads,
               max_tokens,
               /*mask_future=*/true,
               multi_query);
 
-            const ops::Slide slide_lengths_op(2, _sliding_window, layer_in_chunk.dim(1));
+            const ops::Slide slide_lengths_op(2, _sliding_window, layer_in_chunk->dim(1));
             // reuse tmp_lengths
             slide_lengths_op(lengths_mask, tmp_lengths);
             input_lengths_mask = std::make_unique<StorageView>(std::move(tmp_lengths));
           }
 
-          (*_layers[l])(layer_in_chunk,
+          (*_layers[l])(*layer_in_chunk,
                         input_lengths_mask.get(),
                         memory,
                         memory_lengths_mask.get(),
@@ -613,14 +613,14 @@ namespace ctranslate2 {
                         return_normalized_attention(),
                         &position_bias,
                         offset);
-          layer_in_chunk = std::move(layer_out);
+          *layer_in_chunk = std::move(layer_out);
 
           if (layer_attention) {
             alignment_heads.emplace_back(dtype, device);
             ops::Gather(1, 1)(*layer_attention, *heads_to_select, alignment_heads.back());
           }
         }
-        layer_in = std::move(layer_in_chunk);
+        layer_in = std::move(*layer_in_chunk);
       }
 
       if (step == 0) {