Re: design of functions in miltimin

["Andrey V. Panov" <panov at canopus dot iacp dot dvo dot ru>]

Hi.

I disagree. Each call to a cblas function leads to additional for cycle.
There is no much difference when unique call is used (only cost of a function 
call). But in the case of serial 4 calls this leads to 4 for cycles instead 
of one.

On Tuesday 01 July 2003 17:48, Fabrice Rossi wrote:
> Hi.
>
> My understanding of vector calculation optimization is that one should
> rely on BLAS as much as possible. I'm not sure that your code is really
> more efficient than the BLAS code if you use an optimized implementation
> of BLAS such as ATLAS, but of course, I might be wrong. Did you make
> some timing with GSL+ATLAS to compare both solutions?
>
> Fabrice
>
> Andrey V. Panov wrote:
> > I think that the body of take_step() function in
> > multimin/directional_minimize.c :
> >
> > {
> >   gsl_vector_set_zero (dx);
> >   gsl_blas_daxpy (-step * lambda, p, dx);
> >
> >   gsl_vector_memcpy (x1, x);
> >   gsl_blas_daxpy (1.0, dx, x1);
> > }
> >
> > can be replaced by more efficient code:
> >
> > {
> > int i;
> > double dx_temp;
> > for(i = 0; i < dx->size; i++)
> > {
> >   dx_temp = -step * lambda * gsl_vector_get(p, i);
> >   gsl_vector_set(dx, i, dx_temp);
> >   gsl_vector_set(x1, i, gsl_vector_get(x, i) + dx_temp);
> > }
> > }
> >
> > There are also similar parts of code inside miltimin routines which
> > may be
> > replaced.

-- 
Andrey V. Panov
panov /@/ canopus.iacp.dvo.ru