| Re: Faster approach for total(data,dimension) possible? [message #67044 is a reply to message #67043] |
Wed, 24 June 2009 13:53   |
Jeremy Bailin
Messages: 618
Registered: April 2008
|
Senior Member |
|
|
On Jun 24, 12:34 pm, wlandsman <wlands...@gmail.com> wrote:
> On Jun 24, 11:38 am, chris <rog...@googlemail.com> wrote:
>
>> Min and Max approach is two times slower in my case, so this doesn't
>> seem to be a solution. Any other ideas?
>
> Be sure to calculate min and max at the same time, e.g.
> mask1 = max(data,dimen=3,min=mask)
> mask = (mask or mask1) NE 0
>
> But it seems that the best performance is hardware dependent.
> Below are the repeatable times in seconds I get for the different
> methods for a 1536 x 231 x 126 array on different systems.
>
> { x86_64 linux unix linux 7.0
> TOTAL 0.26
> TOTAL(/INTEGER) 0.28
> TOTAL(byte) 0.17
> MINMAX 0.25
>
> (x_86_64 darwin unix Mac OS X 7.06)
> TOTAL 0.24
> TOTAL(/INTEGER) 0.16
> TOTAL(byte) 0.22
> MINMAX 0.24
>
> Since you are getting the best times for the first (TOTAL()) method, I
> suspect your hardware is optimized for floating point calculations.
> If you were to code it in C (i.e. not worry about loops) the quickest
> method should be some variant of ARRAY_EQUAL
> where you stop the comparisons once you find a non-zero element in a
> band. But until ARRAY_EQUAL gets a dimension keyword like MIN and
> MAX I don't think any other IDL method is going to be much faster.
> --Wayne
How about using product? It should be well-optimized for the cases of
multiplying-by-one and multiplying-by-zero:
mask = ~product(data gt 0, 3, /preserve_type)
-Jeremy.
|
|
|
|
comp.lang.idl-pvwave archive
Members
Search
Help
Login
Home
