[SciPy-user] complex vector scalar product: wrong implementation

[Vladimir A. Roudnev]

Fernando Perez wrote:

> There is one important reason to want to have pure non-conjugating 
> functions: performance.  If you are writing code which is using purely 
> real arrays, and dot/inner are at the center of your critical path, 
> you do NOT want constant type checks or no-op conjugations to be 
> taking place.  Now, I am not arguing that the current choice of names 
> was a good one, but there is a very valid reason for having an 
> explicitely, purely real set of functions.

I strongly disagree with the performance argument. Performance problems 
rise when dealing with big arrays that are not supposed to be processed 
in python, but with a native method. It is the high-level language 
(Python) library which is responsible for choosing the right
native method to call. For big arrays type-checking is (OK, expected to 
be) a relatively fast operation, and the proper BLAS call (xDOT or 
xDOTC, or xDOTU when appropriate) must be made on the base of this fast 
type-checking procedure.

BW,
  VR