How to efficiently create an array of libpointers?
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Pico Technology
il 1 Ott 2013
Commentato: Pico Technology
il 7 Ott 2013
Hi,
I am working on a piece of code to create a 2D array of libpointers that can be passed to a shared library. This corresponds to dividing up the memory on a device to capture data for each channel on a device:
nCaptures = 2000000;
num_samples = 64;
tic;
for ch = 1:4
for segment = 1:nCaptures
if(channelSettings(ch).enabled)
rapidBlockBuffer(ch, segment) = libpointer('int16Ptr', zeros(num_samples, 1));
[status.setDataBufferBulk(ch, segment)] = calllib('PS6000', 'ps6000SetDataBufferBulk', handle, ch - 1, ...
rapidBlockBuffer(ch, segment), num_samples, segment - 1, downSampleRatioMode);
else
rapidBlockBuffer(ch, segment) = libpointer('int16Ptr', 0);
end
end
end
toc;
On a Windows 8 64-bit PC with MATLAB 2012b, this code was running for well over 1.5 hours and hadn't completed.
Is the else condition a suitable way of maintaining the array dimensions if a channel on the device is not enabled?
Thanks,
H
2 Commenti
Philip Borghesani
il 2 Ott 2013
I am not sure that creating this many libpointer objects makes sense for any application. More information on the problem you are trying to solve or the system you are trying to implement might help give perspective on alternate solutions.
Risposta accettata
Philip Borghesani
il 2 Ott 2013
Modificato: Philip Borghesani
il 2 Ott 2013
The libpointer code itself is fine but if you did not preallocate rapidBlockBuffer then this code is very slow (order n^2 instead of order n). I added
rapidBlockBuffer(4,nCaptures)=libpointer;
before the ch for loop and find the code without the calllib call will complete in a few minutes. If status.setDataBufferBulk is not preallocated then it should also be.
When rapidBlockBuffer is prealloced there is no need for the else block inserting a dummy pointer.
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