[petsc-dev] the complex dot business

[Jed Brown]

On Mon, Feb 27, 2012 at 10:55, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
>   I'm afraid the sudden appearance of the blas dot for complex numbers
> problem is my fault.
>
>   Traditionally since 199x we never used the complex dot product from blas
> because of the return complex type problem. VecDot_Seq() used #ifdef for
> complex and a simple loop.
>
>   Since some blas norm suck I off-hand told Shri to use dot for norm and
> wasn't thinking the complex case.
>

Most BLAS implementations don't have great code for BLAS level 1 anyway and
it tends to be memory bandwidth limited, so I don't have a problem with
using a simple loop.


>
>   Since then, of course, the complex dot problem has been coming up.
>
>   Maybe it is best to continue to never use complex blas dot and just
> change the VecNorm_ routines to use norm for complex and not dot.? Just
> throw away this silly problem and time sink?


I think we should use norm for norm.
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