[ublas] numeric bindings - computing workspace requirements

Subject: [ublas] numeric bindings - computing workspace requirements
From: Peter Man (plwm2_at_[hidden])
Date: 2011-01-12 07:30:15

Hi all,

I'm currently using the numeric bindings library, however, I'm trying to 
find an easy way of determining the workspace requirements that I need.
As far as I can see, the numeric bindings wrappings around the original 
lapack routines automatically do all the work i.e.

- if not using your own workspace, it ascertains either minimal or 
optimal workspace requirements by passing lwork=-1 to the original 
lapack function.
- creates a temporary workspace according to the computed size
- then the original lapack routine is called using that temporary workspace
- and then the temporary workspace goes out of scope meaning it gets 
destroyed.

However, the user of the wrapped lapack functions doesn't have access to 
the size of this temporary workspace. Since i'm making repeated calls to 
these lapack routines, it seems wasteful that I'm repeatedly creating 
and destroying this temporary workspace. My question is this: have I 
missed something and that the user actually does have some easy way of 
determining the optimal workspace sizes, or should I just create an 
overly large workspace object myself? The problem is that I'm not sure 
how large I should make this workspace object if I choose the latter option.

Thanks,

Peter