Re: [Boost-users] Boost MultiArray and Boost uBLAS - Designed to be used together?

Subject: Re: [Boost-users] Boost MultiArray and Boost uBLAS - Designed to be used together?
From: Bilokon, Paul (paul.bilokon_at_[hidden])
Date: 2010-01-18 05:10:25

Dear Jesse, All,

I'll certainly have a look and if I come up with something useful will let you know.

However, this leads to another question: if MultiArray and Boost uBLAS were not designed to work together, is there a reason for this?

Is it perhaps the case that Boost MultiArray wasn't designed (or optimised) for numerical calculations?

Best wishes,
Paul

-----Original Message-----
From: boost-users-bounces_at_[hidden] [mailto:boost-users-bounces_at_[hidden]] On Behalf Of Jesse Perla
Sent: 14 January 2010 19:08
To: boost-users_at_[hidden]
Subject: Re: [Boost-users] Boost MultiArray and Boost uBLAS - Designed to be used together?

On Jan 14, 7:40 am, "Bilokon, Paul " <paul.bilo..._at_[hidden]> wrote:
> Hi all,
>
> Were Boost MultiArray and Boost uBLAS designed to be used together?
> I.e. can I apply linear algebra operations to Boost MultiArrays and get Boost MultiArrays back?
> If this is impossible / impractical / inefficient, what's the right approach (conversion?).

If this is a one-off problem, you could order the dimensions of the multi_array (fortran vs. C ordering) so that the matrix data you need is contiguous, get the underlying data pointer, go to the right offset by looking at the extents() variable, then use ublas data adaptors to turn the pointer into.  Of course, this is a horrible hack and not generally useful.

As far as I can tell, the right way to do this is:  Create ublas adaptors for multi_array references of dimension 1 and 2.  I am not entirely sure how to do this, but I was told before that looking at the undocumented ublas::shallow_array_adaptor in \boost\numeric\ublas \storage.hpp  might give a template for the 1d version at least.

The other thing I thought about was that the matrix_range class and equivalent for vectors (which is returned from subrange, and is in
matrix_proxy.cpp)   would provide a great template for the iterators,
typedefs, etc. necessary for the adaptor.  I imagine most of the code will just be proxying iterators to the underlying multi_array iterators, etc.

I haven't had a pressing need for this, so might never get around to playing with it.  But if you write it, I am sure everyone on the ublas list would love to have it.
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