Re: [Blitz-support] Blitz array indexing

[Navneet D. <Nav...@in...>]

Hi Amit,

Blitz has tensor notation for such computations. Look at documentation for 
detail. However, when I tried your example with tensor mechanism, blitz 
expression template complains about array C being a 1D array. 

So I don't think that your example will compile without writing for loops. If 
any one has better ideas, you are welcome.

In precisely these kind of situtations, one would like to use blitz iterators. 
However, blitz iterators are associated with array class. So this makes them 
cumbersome to use in these kind of expresions -- should one use 3 different 
iterators in this example or one singe iterator with position function to 
access other elements. 

For these kind of situations, I wrote DomainIter class some months back. I 
have been using it for quite some time now. So Julian, may we should add this 
class to blitz cvs repository.

I am attaching required files and an example file showing the common use. For 
details, you may like to look at documentation in the file.


I hope this helps
-navneet

On Monday 10 May 2004 19:16, Ami...@se... wrote:
> Hi,
>
> I am trying to implement something on the following lines:
>
> Array<float,3> A, B;  //size Nx*Ny*Nz
> Array<int,3> index; // size Nx*Ny*Nz
> Array<float,1> C; // A look up table
> ..
> ..
> ..
> for(k=0; k<Nz; k++)
>      for(j=0; j<Ny; j++)
>           for(i=0; i<Nx; i++)
>        A(i,j,k)+=B(i,j,k)*C(index(i,j,k));
>
> Can I use an efficient simple statement in Blitz using "Range" ?
>
> eg:
>
> For range objects I, J, K
>
> A(I,J,K)+=B(I,J,K)*________
>
> I do not know what to fill in the blanks !!  C(index(I,J,K)) does not work.
>
> Thanks
>
> Rgds,
> Amit
>
>
>
> _______________________________________________
> Blitz-support mailing list
> Bli...@oo...
> http://www.oonumerics.org/mailman/listinfo.cgi/blitz-support

-- 
Navneet DALAL            http://lear.inrialpes.fr/people/Dalal
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