| Re: Compiling file with many functions: huge performance difference between IDL and IDLDE [message #38645 is a reply to message #38531] |
Thu, 18 March 2004 12:50   |
btt
Messages: 345
Registered: December 2000
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Senior Member |
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Sidney Cadot wrote:
> Mirko Vukovic wrote:
>
>>> P.S. the reason we're doing this is that we need to implement a
>>> string-based map with optiomal performance, like this:
>>>
>>> FUNCTION f_tom
>>> RETURN, 123
>>> END
>>>
>>> FUNCTION f_dick
>>> RETURN, 456
>>> END
>>>
>>> FUNCTION f_harry
>>> RETURN, 789
>>> END
>>>
>>> FUNCTION f, name
>>> CATCH, error_status
>>> IF error_status EQ 0 THEN RETURN, -1
>>> RETURN, call_function("f_" + name)
>>> END
>>
>>
>>
>> Out of curiosity, would a structure work here:
>> a={f_tom:123,f_dick:456,f_harry:789...} ?
>>
>> It could be created using create_struct.
>>
>> Retrieve info using
>> a=str.f_dick
>>
>> Curious minds want to know :-)
>
>
> Your idea is sound, but I am not aware of a way to retrieve the index of
> a tag-name based on its name.
>
> You assume that "f_dick" is available at compile time, whereas I need to
> resolve the string at runtime. Something like this would work:
>
> i = TAG_INDEX("f_dick", str)
> value = str.(i)
>
> ... But only if functionality to get a tag index can be retrieved from a
> struct (anyone knows how to do this?) and if its fast, i.e. if IDL
> implements it via a hash table or similar.
>
How about this ?
IDL> print, tag_index(['color', 'clip', 'banana'], !P, count = count) &
print, count
4 3 -1
2
;-----start
FUNCTION TAG_INDEX, tagName, str, count = count
tags = TAG_NAMES(str)
n = n_elements(tagName)
tag_index = LonArr(n, /noZero)
Count = 0L
For i = 0L, n-1 Do begin
tag_index[i] = (WHERE(tags EQ StrUpCase(tagName[i]), cnt))[0]
Count = Count + (cnt GT 0)
EndFor
Return, tag_index
END
;-----finish
Ben
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