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| Re: initializing arrays [message #49050 is a reply to message #49014] |
Wed, 14 June 2006 15:10  |
biophys
Messages: 68
Registered: July 2004
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Member |
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On a 1GB 3.0GHZ linux machine, the 3rd method is much faster if the
array size is small(eg smaller than fltarr(300,300)). otherwise, the
other two methods are faster(about twice as fast). The performance of
replicate and make_array are always close. I am not sure if it holds
for other platforms.-bp
Marshall Perrin wrote:
> Ben Tupper <btupper@bigelow.org> wrote:
>> johnadams_1980@yahoo.com wrote:
>>> Hi All,
>>>
>>> How do you initialize an array to a specific value without using a for
>>> loop?
>>>
>>> Thanks,
>>> KL
>>>
>> You have choices...
>>
>> arr = REPLICATE(7.0, [32,5])
>>
>> arr = MAKE_ARRAY([32,5], VALUE = 7.0)
>>
>> arr = FLTARR(32,5) + 7.0
>
> And somewhat oddly, all three of these seem to be about equal in
> execution speed for me (tested on a Mac G4 creating a [1000,10000]
> array of floats filled with 7s). I would've predicted the third one
> to be substantially slower due to all thos the additions, but it
> doesn't seem to be. Maybe the IDL compiler is doing something clever
> under the hood? (Which is good news, anyway, since that's the one I use
> most often myself!)
>
> - Marshall
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