[Numpy-discussion] strange sin/cos performance

Hans Meine meine@informatik.uni-hamburg...
Tue Aug 4 13:46:39 CDT 2009


On Tuesday 04 August 2009 19:19:22 Andrew Friedley wrote:
> OK, have some interesting results.  First is my array creation was not
> doing what I thought it was.  This (what I've been doing) creates an
> array of 159161 elements:
>
> numpy.arange(0.0, 1000, (2 * 3.14159) / 1000, dtype=numpy.float32)

Aaaaah.  And I wondered why taking the sin/cos of 1000 elements took so 
long... ;-)  (actually, I would've used larger arrays for benchmarking to 
begin with)

Indeed, the value range fixes stuff here (Linux, GCC/amd64, Xeon X5450 @ 
3.00GHz, NumPy 1.3.0), too:

Before:

float64 10 loops, best of 3: 54.2 ms per loop
float32 10 loops, best of 3: 7.62 ms per loop

After:

float64 10 loops, best of 3: 6.03 ms per loop
float32 10 loops, best of 3: 3.81 ms per loop

Best,
  Hans



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