[PD-dev] pvoc example and rsqrt~

[Julius Orion Smith III]

In all practical signal processing systems I have seen, overflows saturate 
to the largest magnitude (and correct sign), while underflows are quietly 
set to zero.  Status bits may be set to indicate these actions, and they 
can be polled and cleared at will, but the signal processing itself always 
goes on full speed as best it can. -- jos

On Mon, 29 Dec 2003, Thomas Grill wrote:

> Hi Miller, hi all,
> 
> i came across a strange thing when testing the Altivec SIMD 
> implementation with my favorite example, namely 04.fft/09.pvoc.pd .
> It seems that the phase propagation is dependent on the fact that 
> rsqrt~ (0) delivers a valid non-zero value of about 1.e+19. (well, 
> which non-zero value is irrelevant)
> If rsqrt~ (0) = 0, which would make more sense to me (given the zero 
> checks in /~ ) the example is silent. (what almost drove me nuts, btw. 
> )
> 
> Although i already asked before, i'd be interested about the common 
> behaviour of objects that are endangered to deliver NANs. Should these 
> cases always be trapped and bashed to zero? To know that would help me 
> a lot with the proper SIMD implementation.
> 
> best greetings,
> Thomas
> 
> 
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-- 
Julius (jos at ccrma.stanford.edu)