[Coin-discuss] CoinPackedMatrix memory management

[Laszlo Ladanyi]

On Wed, 30 Jul 2003, Jörg Herbers wrote:

> When building a sparse matrix with several ten thousand non-zero entries 
> with CoinPackedMatrix, I have run into performance problems: When I 
> successively added columns without manual actions wrt. memory management 
> (matrix is column-ordered), it took several minutes to build the matrix. 
> When reserving memory before (via CoinPackedMatrix::reserve), initialization 
> times reduce to fractions of a second.
> 
> I have found that a reallocation is done every time a column is added (in 
> resizeForAddingMajorVectors) if memory is not allocated before. Effectively, 
> all data vectors are newly allocated and copied.
> 
> Clearly, manual allocation via reserve() is always possible, but the 
> calculation of the number of non-zeros can be cumbersome. Instead, it would 
> be better to have an enhanced memory management, e.g. by using "realloc" 
> style memory management (which does not always copy the memory blocks) and 
> by reserving extra space upon each resize operation (i.e. always 
> reallocating for a given "delta" of additional elements). Is there anything 
> planned in that direction?

Actually, this extra space reservation is in the CoinPackedMatrix class. The
extraGap_ and extraMajor_ members indicate the extra percentage to be
allocated for new nonzeros and columns (for column major ordered matrix). 
At least that was the plan. I just looked at the code and found a stupid bug.
Fixed it and committed it.

Please, check it out and test it.

> 
> Jörg
> 
> _________________________________________________________________
> Help STOP SPAM with the new MSN 8 and get 2 months FREE*  
> http://join.msn.com/?page=features/junkmail
> 
> _______________________________________________
> Coin-discuss mailing list
> Coin-discuss at www-124.ibm.com
> http://www-124.ibm.com/developerworks/oss/mailman/listinfo/coin-discuss
> 

Thanks for the bug report!

--Laci