Fix LSTM Ct clipping without bias (Issue #27224)

chaya2350 · chaya2350 · commit 14393039dad7 · 2026-02-04T09:57:57.000+02:00
diff --git a/onnxruntime/core/providers/cpu/rnn/uni_directional_lstm.cc b/onnxruntime/core/providers/cpu/rnn/uni_directional_lstm.cc
@@ -583,7 +583,8 @@ void UniDirectionalLstm<T>::GateComputations(
     for (int i = 0; i < hidden_size_; ++i) {
       pC_prev_clipped[i] = pC_cur[i];
     }
-    clip_with_bias_ptr_(clip_, nullptr, pC_prev_clipped, hidden_size_);
+    // Ct clipping should not add bias; always use clip_ignore_bias.
+    deepcpu::clip_ignore_bias(clip_, nullptr, pC_prev_clipped, hidden_size_);
 
     activation_h_.func(pC_prev_clipped, pC_prev_clipped, po, pH, hidden_size_, activation_h_.alpha, activation_h_.beta);
 

Original file line number	Diff line number	Diff line change
`@@ -583,7 +583,8 @@ void UniDirectionalLstm<T>::GateComputations(`
`583`	`583`	`for (int i = 0; i < hidden_size_; ++i) {`
`584`	`584`	`pC_prev_clipped[i] = pC_cur[i];`
`585`	`585`	`}`
`586`		`- clip_with_bias_ptr_(clip_, nullptr, pC_prev_clipped, hidden_size_);`
	`586`	`+ // Ct clipping should not add bias; always use clip_ignore_bias.`
	`587`	`+ deepcpu::clip_ignore_bias(clip_, nullptr, pC_prev_clipped, hidden_size_);`
`587`	`588`
`588`	`589`	`activation_h_.func(pC_prev_clipped, pC_prev_clipped, po, pH, hidden_size_, activation_h_.alpha, activation_h_.beta);`
`589`	`590`