[SciPy-dev] linalg.flapack strange argument in *gesdd

Pearu Peterson pearu at scipy.org
Wed May 18 02:32:44 CDT 2005



On Wed, 18 May 2005, Nils Wagner wrote:

> Hi all,
>
> A help (linalg.flpack) yields
>
> This module 'flapack' is auto-generated with f2py (version:2.46.243_1985)
>
> u,s,vt,info = 
> sgesdd(a,compute_uv=1,lwork=(compute_uv?4*minmn*minmn+MAX(m,n)+9*minmn:MAX(14*minmn+4,10*minmn+2+25*(25+8))+MAX(m,n)),overwrite_a=0)
>     u,s,vt,info = 
> dgesdd(a,compute_uv=1,lwork=(compute_uv?4*minmn*minmn+MAX(m,n)+9*minmn:MAX(14*minmn+4,10*minmn+2+25*(25+8))+MAX(m,n)),overwrite_a=0)
>     u,s,vt,info = 
> cgesdd(a,compute_uv=1,lwork=(compute_uv?2*minmn*minmn+MAX(m,n)+2*minmn:2*minmn+MAX(m,n)),overwrite_a=0)
>     u,s,vt,info = 
> zgesdd(a,compute_uv=1,lwork=(compute_uv?2*minmn*minmn+MAX(m,n)+2*minmn:2*minmn+MAX(m,n)),overwrite_a=0)
>
> What is the meaning of compute_uv?4*minmn*minmn ?

What you see in lwork initial value is given in C syntax. The 
corresponding complete C statement would be

   ( <condition> ? <return value if condition is true> : <return value if not>)

Pearu




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