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From Marshall Schor <...@schor.com>
Subject Re: Delta CAS
Date Tue, 08 Jul 2008 22:08:26 GMT
Thilo Goetz wrote:
> Marshall Schor wrote:
>> Thilo Goetz wrote:
>>> Bhavani Iyer wrote:
>>>> Hi Thilo,
>>>>
>>>> There are two separate requirements being addressed here:
>>>> 1) delta CAS for optimizing remote services.
>>>>      Here its agreed that there should be no measurable overhead 
>>>> when there
>>>> is no remoting.
>>>>      There will be a single test against the high water mark.  The 
>>>> high
>>>> water mark defaults to 0.  Only when the high
>>>>      water mark is set to a value greater than 0 is logging of  CAS
>>>> operations on FSs below the high water mark enabled.
>>>> 2)  Journaling for debugging  aggregate components.
>>>>     This capability is for Core UIMA as well as for remote 
>>>> services. This
>>>> will have some additional overhead and will be have to be 
>>>> explicitly enabled
>>>> by the aggregate controller for a component. Basically the aggregate
>>>> controller enables journaling by setting the high water mark before 
>>>> the call
>>>> to process.
>>>>
>>>> Regarding using the high water mark, this is already being used for 
>>>> merging
>>>> CAS.
>>>
>>> That's not a good thing, and certainly no justification of using
>>> the same design here.  
>> Can you say more about why this is not a good thing?  I see it as an 
>> internal design detail.
>
> Precisely.  It's an implementation detail of the CAS heap that
> we should be able to change -- that we must be able to change
> if we would like to improve on the heap.  
We could change it if we found a better approach.
> The CAS heap and
> in particular the way it grows is a major performance bottleneck
> for large documents.  If we have other parts of UIMA depend on
> the (bad) implementation details now, we'll never be able to
> improve on the design.
Hmmm, I guess I was thinking that if we wanted to change this in the 
future, we could.  I agree it would be more difficult;  we've changed 
things like this before using the refactoring tools that let you see 
pretty clearly various dependencies...

-Marshall

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