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From "Andrew C. Oliver" <acoli...@apache.org>
Subject Re: ValueRecordsAggregate performance branch
Date Fri, 28 Feb 2003 19:02:03 GMT
Height, Jason wrote:

>Andy,
>
>Ok I guess that I don't completely understand what is going on then! I
>thought that the existing insertCell method would be all that is required,
>without the need to decomposing the cell inorder to save the cell ie simply
>save the object reference as was originally being done, but in a structure
>that would enable fast row lookup and fast row cell iteration.
>  
>
Thats what takes too much memory.

>Since I don't exactly know what is going on I think that it may be best if
>you do the merge of this class into the main branch. After which I will
>supply another patch to 9576.
>  
>
Okay.  Danny is looking into it.  If I do it, it will have to wait.

-Andy

>Jason
>
>
>-----Original Message-----
>From: Andrew C. Oliver [mailto:acoliver@apache.org] 
>Sent: Thursday, 20 February 2003 23:42
>To: Height, Jason
>Subject: Re: ValueRecordsAggregate performance branch [Scanned For Viruses]
>
>Height, Jason wrote:
>
>  
>
>>Andy,
>>
>>Ok I think that I roughly understand what you are trying to do on the 
>>performance branch wrt ValueRecordsAggregate in that you are trying to 
>>store the contents of a cell as a primitive rather than as an object 
>>(LabelSST etc). I can see that this will provide memory improvements, 
>>according to OptimizeIt a LabelSST object occupies 30bytes whereas you 
>>are only storing the index to the string which is a double ie 8 bytes, 
>>so there is a 22 byte overhead per LabelSST object.
>>
>>    
>>
>Note that I do this slightly wastefully, Only 4 bytes are really 
>required, but in order to make things clean and not have yet another 
>array, its stored in the same place as #s.
>
>  
>
>>However if I am going to iterate over each cell wont there will be 
>>some performance problems in that the ValueRecordsAggregate will need 
>>to instanciate and then GC a lot of objects? So although you have 
>>saved memory for storing the workbook, additional memory and 
>>processing is required to use the workbook!
>>
>>    
>>
>Eventually.  I'm into refactoring and stuff.  So this change is pretty 
>much a huge refactoring.  Doing it all at once seems wrought with 
>disaster (at least to me).  My thought was 1st graft the new method into 
>existing structures.  Then later make another pass of optimizations 
>(maybe after 2.0, not sure). 
>
>  
>
>>I think that the VRAIterator is FANTASTIC. It fixes my performance 
>>problems with my DBCell etc patch.
>> 
>>
>>    
>>
>Cool.
>
>  
>
>>Why couldn't we just implement the data structures for quick access 
>>without decomposing them from the java objects? In my opinion (for 
>>what it is worth) the conversion from and to the java object 
>>representations is not a good idea, it makes the whole thing much more 
>>complicated, needs to expose additional methods, will be harder to 
>>maintain and the CPU time required to create and maintain the data in 
>>both directions may be more significant (and not worth the memory saving).
>>
>>    
>>
>In due time.  Note though that some decomposition is necessary to make 
>the code manageable (even if it wastes memory).  I can't imagine bit 
>twiddling on byte arrays of this stuff.  Furtheremore if the file were 
>treated too flatly, we'd end up doing lots of extra array copies 
>whenever an insert was done in the middle...  Still I think memory 
>mapping should be a goal for a post-2.0 release (formulas and graphing 
>first).
>
>  
>
>>PS Ever noticed that the Record object holds onto the byte data array 
>>from which it is created. It doesn't need to. Basically it is wasting 
>>as much memory as the size of the excel file that was opened. Is this 
>>intentional?
>>
>>    
>>
>Every record does?  If so, that is a big mistake IMNSHO.
>
>Anyhow, no need to write this privately.  I'm thick skinned when the 
>conversation is technical :-).  We sould eliminate the record holding 
>onto the data if it indeed is doing that.  Thats a monumental waste of 
>memory.
>
>Oh yeah.. I meant to propose you a committer....gotta do that this morning.
>
>-Andy
>
>  
>
>>Jason
>>
>>
>>
>>    
>>
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