Re: [Cmusphinx-devel] Fix to Dither

[Peter W. <pet...@ve...>]

Hi Rita,

Yes, removing Dither would work.  But then every system using dither 
would be non-repeatable.

Is there any reason that Dither should be really random?  Is there some 
subtle problem that will be caused by every utterance being dithered by 
the same sequence of numbers?

P


Rita Singh wrote:
> Hi Peter,
>
> The other alternative is to set log 0 to a reasonable noise floor
> value (such as -4), and disable dither when you do that. Could you try
> that out and let us know what you observe?
>
> -Rita
>
>
> On Mon, Apr 20, 2009 at 3:13 PM, Peter Wolf <pet...@ve...> wrote:
>   
>> Well, there might be... but a few unit tests will find them.  Floating
>> point numbers are wonderfully sensitive :-)
>>
>> BTW I have checked in the fix, and a corresponding unit test to GitHub.
>>
>> Joe Wölfel wrote:
>>     
>>> I agree.  It's difficult to test anything that includes random
>>> behavior.    I guess my question is will this be enough?  Are there
>>> other sources of randomness that may affect results?
>>>
>>>
>>> On 20 avr. 09, at 14:26, Peter Wolf wrote:
>>>
>>>       
>>>> Hello Sphinx4 developers,
>>>>
>>>> I was just tracking down a bug where recognizing the same utterance
>>>> twice in a row did not produce identical scores.  They should, since I
>>>> was using BatchCMN.
>>>>
>>>> I discovered that the problem was in Dither which uses a Random number
>>>> generator.  The generator was not reset at every DataStartSignal, so
>>>> recognition behavior was determined by the utterances that came before.
>>>>
>>>> I am writing very sensitive tests that prove correctness in my app by
>>>> comparing scores.  So I need atomic behavior from Sphinx4.  I would
>>>> argue that repeatable behavior is required for many uses.
>>>>
>>>> So, here is my proposed fix to Dither (in bold).
>>>>
>>>> Comments, thoughts?  Am I missing something important?
>>>>
>>>>     /**
>>>>      * Returns the next Data object being processed by this Dither, or
>>>> if it is
>>>>      * a Signal, it is returned without modification.
>>>>      *
>>>>      * @return the next available Data object, returns null if no Data
>>>> object is
>>>>      *         available
>>>>      * @throws DataProcessingException
>>>>      *             if there is a processing error
>>>>      * @see Data
>>>>      */
>>>>     public Data getData() throws DataProcessingException {
>>>>         Data input = getPredecessor().getData();
>>>>         getTimer().start();
>>>>         if (input != null && input instanceof DoubleData) {
>>>>             applyDither(((DoubleData) input).getValues());
>>>>         }
>>>> *        else if( input instanceof DataStartSignal ) {
>>>>             /**
>>>>              * reset the dither at the beginning of each utterance
>>>>              * this ensures that a given combination of
>>>> utterance/parameters/model
>>>>              * will always behave the same way
>>>>              *
>>>>              * otherwise it will be affected by utterances that came
>>>> before
>>>>              */
>>>>             random = new Random(0);
>>>>         }*
>>>>         getTimer().stop();
>>>>         return input;
>>>>     }
>>>>
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>>>       
>>
>> ------------------------------------------------------------------------------
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>>     
>
>