mix LM

Andreas Stolcke stolcke at speech.sri.com
Tue Sep 3 09:13:18 PDT 2002

In message <3D74DD88.8E7C2BD8 at inzigo.com>you wrote:

> His first suggestion reminds me the mixture LM. Actually I made some
> tests on the interpolattion approach, including class + word LM. I
> always found that the perplexity (and WER) is a linear function of the
> interpolation parameter (Lambda), so the best results are always at the
> ends, which makes the interpolation trivil. Did I miss something, or it
> is the case for some domains?


how did you find the best interpolation weight?  I hope you didn't
use trial-and-error and used the compute-best-mix script instead.
In my experience the perplexity is not a linear function of lambda,
unless maybe your class-based LM is very bad.  Rather, ppl should be 
U-shaped function as lambda varies between 0 and 1.


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