sorry went off list.
to clarify, i am fine with wrapping of the output, so if i hit the higher limit of 32bit it should just start from zero again. it's crucial that it never stops counting though...
---------- Forwarded message --------- From: Simon Iten itensimon@gmail.com Date: Tue, Feb 18, 2020, 10:26 Subject: Re: [PD] rpole bug? To: Orm Finnendahl orm.finnendahl@selma.hfmdk-frankfurt.de
thanks to both of you!
a related question:
what would then be the preferred way to count up (only integers needed) to very high numbers in PD without precision loss? am i better of with line~ or even metro? the speed of counting should be adjustable from very low values to about 8000 hz. i tried a phasor~ solution but ran into the precision loss problem on very slow input rates to phasor...
On Sat, Feb 15, 2020, 18:38 Orm Finnendahl < orm.finnendahl@selma.hfmdk-frankfurt.de> wrote:
Hi,
to circumvent this limitation you can use a second structure (e.g. using a second rpole~) to count the overflows, resetting the first rpole when it reaches a threshold.
-- Orm
Am 15. Februar 2020 18:24:48 MEZ schrieb Christof Ressi < info@christofressi.com>:
This expected behavior due to limited precision of floating point numbers. When a float gets larger and larger, it gradually loses precision in the lower bits, because the mantissa has a fixed size (see https://en.wikipedia.org/wiki/IEEE_754).
There will be a point where the precision loss exceeds the size of your input, so the filter will just stop accumulating. In your case, the input is "1". Floating point numbers have a mantissa of 2^23 (without the sign bit), so the largest whole number you can represent without truncating lower bits is 2^23 = 8,388,608. This is the limit you've experienced in your patch.
BTW, this is also the reason why you get artifacts when indexing an audio buffer with a large float index.
Interestingly, I couldn't immediatly reproduce this behavior on my system (Pd 0.50.2 Windows 32-bit), the limit would be about 8 times as large as yours. I think the reason is that the code keeps the filter state in an intermediate higher precision register, so the accumulation is not immediately lost. When I run your patch with [block~ 1], each accumulation step has to be written to an actual 32-bit float, and I can indeed reproduce your observation.
Christof On 15.02.2020 17:36, Simon Iten wrote:
i have a strange behaviour with rpole, see attached patch.
basically it stops accumulating at a certain point (depending on the input value) ist this a “rounding” problem?
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Orm Finnendahl Komposition HfMDK Eschersheimer Landstraße 29-39 60322 Frankfurt _______________________________________________ Pd-list@lists.iem.at mailing list UNSUBSCRIBE and account-management -> https://lists.puredata.info/listinfo/pd-list