Re: [pygsl-discuss] where is the time consumed in this program?

[Pierre S. <p.s...@gs...>]

Dear Julien,

	I did not get the problem immediately but here it is:

- with numx.arange(0,1) you allocate an array of integers. The 
interpolation code uses internally doubles, so you have to enforce that 
they will be made float arrays (the native C double type, typically 
numx.float) so use .astype(numpy.float_) or multiply them with 0.1

- you can check if pygsl had to transform the basis type of the vector 
with  pygsl.init.vector_transform_counter(). Call it before and after 
the function in question and you will see.

- if you share code, please be aware that numpy, numarray or Numeric 
could be the array package. These packages interchange quite nicely, but 
that could also cost time, even if not on that scale as your example does.

- there are two modules: spline and interpolation. They both provide the 
same functionality but spline makes internal copies of the vectors x and 
y. This can save quite some cycles here.  Given that you want to 
interpolate in large arrays, it can be that this is not an option.

- spline provides the method eval_vector. If you have an vector you need 
  interpolation values for, this will make a huge difference. If you 
need the same function for the interpolation drop me a line and I will 
add it (or for eval_deriv, or eval_integ ....)


Sincerely yours
	Pierre

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