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Re: () and execution speed [message #44950] Fri, 29 July 2005 09:27 Go to previous message
Ken Mankoff is currently offline  Ken Mankoff
Messages: 158
Registered: February 2000
Senior Member
On Fri, 29 Jul 2005, Gert wrote:
> I just played with and array of structures, each structure
> containing a (float) images. If i do
>
> SomeProc, psData[NumStruct].flIm[1:1000]
>
> or
>
> SomeProc, (psData[NumStruct].flIm)[1:1000]
>
> then the result is the same, but the second runs much slower.
> Anyone knows why this is so? My guess is that in the second run, a
> copy of the array is made.

Sounds like a good guess. A compiler optimization might be able to
catch the above special case, but () changes the precedence. You
could have (x[y].z +1)[42] so direct memory access won't work.

> I would be interested to find out if there are more 'pitfalls' out
> there.
TVSCL? The decompose keyword to DEVICE?

-k.
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