[PD] Maybe I'm pushing dynamic object creation too far

[Mathieu Bouchard]

On Thu, 3 Feb 2011, Roman Haefeli wrote:

> In your situation I'd try to do everything that doesn't necessarily need
> to happen in 0 logical time to extend to > 0 logical time. Unless you
> really need the new tables immediately after the buffer was filled, I'd
> suggest to copy them over 'slowly'.

BTW, merely creating a table is taking a lot of time, especially as the 
table's a_vec is allocated using getbytes(), and getbytes() takes the time 
to fill the whole 300000*4 bytes (or 300000*8 bytes) with carefully 
polished zeroes.

In addition, OSX's allocator for large chunks of memory does a mmap() just 
on linux, but unlike on linux, mmapping new memory on osx is annoyingly 
slow (perhaps also another kind of zero-polishing). However, I can't tell 
you whether this happens at the time of mmap(), or at the time of starting 
to write in a new page of RAM (a 4k block), but this does not matter, as 
getbytes() forces all pages to spring into existence at the same time.

> One approach once mentioned by Miller Puckette is to do array copying by 
> doing it in the audio domain within an upsampled sub-patch. This would 
> make DSP drop-outs during array copying much less likely.

The table is still being cleared anyway, once or twice, before it's filled 
with the real content, and it uses up that much of space in the SRAM too 
(cache). This happens every time you create or resize an array.

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| Mathieu Bouchard ---- tél: +1.514.383.3801 ---- Villeray, Montréal, QC