Re: [Lapackpp-devel] bugs

[Do bi <mrc...@ya...>]

Please can you hint me on how to reduce the memory needs of a 10^5 x 10^5 Matrix in Lapackpp? 
  1) How can I use floats instead for the matrix?
  2) What are the options in Lapack in terms of taking advantage of the symmetry, and using just half the matrix, and still solve A . x = b ?
   Please just hint me on what you would do.
  Regards
  Donald.

Christian Stimming <sti...@tu...> wrote:
  Am Freitag, 4. August 2006 18:57 schrieb Do bi:
> Hi Christian sorry I mistakenly sent to your personal address the first
> time. This is my mportant enquiry:
>
> I noticed that LaGenMatDouble cannot be a size more than (10000,10000).
> Please tell me what to do. I need larger matrices.
> Thanks.

Have you spent some thought about the required memory for the actual storage 
of a 10^4 x 10^4 general matrix? Obviously it has 10^8 entries. The "double" 
data type needs 8 bytes each ("float" needs 4 bytes), so this matrix would 
need 8*10^8 bytes in memory or in other words roughly 800 MBytes (in one 
continuous block). You don't have that amount of memory available. That's the 
whole point of all the other matrix data types which can be used if you don't 
need one "general dense" matrix (but instead any kind of symmetry or 
triangularity or whatever.)

So, no, it's not a bug of lapack/lapackpp that you cannot create 
LaGenMatDouble of that size. You cannot do this unless you're on some kind of 
supercomputer. You have to formulate your problem in a different way so that 
you don't need a LaGenMatDouble.

Christian


 		
---------------------------------
How low will we go? Check out Yahoo! Messenger’s low  PC-to-Phone call rates.