Re: [PD] nearest power of 2
On Fri, 12 Dec 2008, hard off wrote:
what's the easiest way for pd to find the nearest power of 2 for any float?
depends how you define «nearest». multiplication-wise, 92 is closer to 128
than to 64, because 92*92 > 64*128, whereas addition-wise, it's closer to
64 because 92+92 < 64+128.
For nearest powers of something, I'd use the multiplication-wise
definition, whereas for nearest multiples of something, I'd use the
addition-wise definition.
To get the position of the highest bit of x, you can do log(x)/log(2),
though there is an int-only algorithm in gridflow.h:
#define Z(N) if ((x>>N)&(((typeof(x))1<>=N; i+=N; }
static int highest_bit(uint32 x) {int i=0;Z(16)Z(8)Z(4)Z(2)Z(1)return i;}
... this splits a number in two sets of bits repeatedly to find where the
top bit is.
However, I suspect that log(x)/log(2) could be faster than the version
without log, because interpretation of pd patches is slow.
when you have the highest bit you have the previous-or-equal power-of-two
as 1
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Re: [PD] nearest power of 2
http://puredata.hurleur.com/sujet-1953-sample-slicer-user-selectable-slices scroll down the page a bit to get the latest revised version. (oh, and you have to log in to the pd forum to be able to see and download the attachments) ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list
Re: [PD] nearest power of 2
Hardoff* has actually :-) Uses bonk~ and works bloody well.
*is there a link for that somewhere?
On 12 Dec 2008, at 00:25, Kyle Klipowicz wrote:
This is neat. Please share your continued research in this
territory. Also, has anyone made a beat slicer that chops up a sound
file based on transients?
~Kyle
On Thu, Dec 11, 2008 at 11:07 AM, hard off wrote:
may as well post the patch i guess. actually it just gets the NEXT
power of 2, not the nearest, but that is fine for my purpose - which
is to decide how many slices to make in a sound file to cut it into
individual beats.
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Re: [PD] nearest power of 2
This is neat. Please share your continued research in this territory. Also,
has anyone made a beat slicer that chops up a sound file based on
transients?
~Kyle
On Thu, Dec 11, 2008 at 11:07 AM, hard off wrote:
> may as well post the patch i guess. actually it just gets the NEXT power
> of 2, not the nearest, but that is fine for my purpose - which is to decide
> how many slices to make in a sound file to cut it into individual beats.
>
>
>
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Re: [PD] nearest power of 2
This might be silly, but here are three abstractions I made a couple years or so when I was learning... the "nearest" one defaults to the higher value for numbers halfway between. Matt > Date: Fri, 12 Dec 2008 00:48:48 +0900 > From: "hard off" > Subject: [PD] nearest power of 2 > To: "Pd List" > Message-ID: ><161320dd0812110748w620d032g7b9bdff22d2f4...@mail.gmail.com> > Content-Type: text/plain; charset="iso-8859-1" > > what's the easiest way for pd to find the nearest power of 2 for any float? > > > so 10 would give a result of 8, > 53 would give a result of 64, > > etc.. > > > http://en.wikipedia.org/wiki/Power_of_two#Algorithm_to_convert_any_number_into_nearest_power_of_two_number > -- next part -- > An HTML attachment was scrubbed... > URL: > http://lists.puredata.info/pipermail/pd-list/attachments/20081212/bb3be031/attachment-0001.htm > > -- nextpowoftwo.pd Description: Binary data lastpowoftwo.pd Description: Binary data nearestpowoftwo.pd Description: Binary data ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list
Re: [PD] nearest power of 2
Hi, one could also use expr pow(2, int(log($f1)/log(2)+0.5)) which takes the dual log, rounds that to the nearest integer and calculates the dual power again. gr~~~ Am 11.12.2008 um 18:02 schrieb hard off: > ah don't worry. the bitwise operators in pd correspond exactly to > the process in that wikipedia article. couldn't guess it would be > that easy. > > > ___ > Pd-list@iem.at mailing list > UNSUBSCRIBE and account-management -> > http://lists.puredata.info/listinfo/pd-list ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list
Re: [PD] nearest power of 2
may as well post the patch i guess. actually it just gets the NEXT power of 2, not the nearest, but that is fine for my purpose - which is to decide how many slices to make in a sound file to cut it into individual beats. nextpow2.pd Description: application/extension-pd ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list
Re: [PD] nearest power of 2
ah don't worry. the bitwise operators in pd correspond exactly to the process in that wikipedia article. couldn't guess it would be that easy. ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list
[PD] nearest power of 2
what's the easiest way for pd to find the nearest power of 2 for any float? so 10 would give a result of 8, 53 would give a result of 64, etc.. http://en.wikipedia.org/wiki/Power_of_two#Algorithm_to_convert_any_number_into_nearest_power_of_two_number ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list
