shithub: opus

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Adding extra constraint to avoid saturation for SSE/AVX2

When implementing using SSSE3 or AVX2, our dot products can saturate
if two adjacent weights sum to more than 127.

--- a/dnn/training_tf2/lpcnet.py

+++ b/dnn/training_tf2/lpcnet.py

@@ -131,7 +131,10 @@

         self.c = c

     def __call__(self, p):

-        return K.clip(p, -self.c, self.c)

+        # Ensure that abs of adjacent weights don't sum to more than 127. Otherwise there's a risk of

+        # saturation when implementing dot products with SSSE3 or AVX2.

+        return self.c*p/tf.maximum(self.c, tf.repeat(tf.abs(p[:, 1::2])+tf.abs(p[:, 0::2]), 2, axis=1))

+        #return K.clip(p, -self.c, self.c)

     def get_config(self):

         return {'name': self.__class__.__name__,

-- 

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