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Index › Programming Questions & Help › Syntax Questions › arraycopy / subset / append -- which is fastest

ch Junior Member Offline Posts: 65

arraycopy / subset / append -- which is fastest? Oct 21st, 2007, 10:15pm   hi all can anyone who knows what's going at the heart of p5 tell me which of these two would the fastest way to shift an array over by 1, and fill in a value (basically using it keep a running average): len = hp.length; hp = append(subset(hp, 1, len - 1),f); or len = hp.length; arraycopy(hp,1, hp,0,len-1); hp[len-1] = f; thanks!

fry YaBB Moderator Offline Posts: 2623 mass, usa	Re: arraycopy / subset / append -- which is fastes Reply #1 - Oct 21st, 2007, 10:54pm   append() and subset() are slow(ish), arraycopy is fast. i can't remember whether arraycopy works if the source and destination array are the same, you'll have to check. if not, it might be for() loop time. fastest of all is to use % (modulo) to move through the array, rather than shifting it over.

ch Junior Member Offline Posts: 65	Re: arraycopy / subset / append -- which is fastes Reply #2 - Oct 22nd, 2007, 1:49am   great, thanks fry (for others: modulo technique is summarised here: http://processing.org/discourse/yabb_beta/YaBB.cgi?board=Programs;action=display;num=1185202099;start=2#2 )

djones Junior Member Offline Posts: 76 Ontario, CANADA

Re: arraycopy / subset / append -- which is fastes Reply #3 - Oct 22nd, 2007, 6:20pm   ch wrote on Oct 21st, 2007, 10:15pm: hi all can anyone who knows what's going at the heart of p5 tell me which of these two would the fastest way to shift an array over by 1, and fill in a value (basically using it KEEP A RUNNING AVERAGE): ... thanks! This was a trick question! The fastest way to keep a running average is to avoid shifting the array elements completely.  Just treat it like a circular array and keep an index to the "last" element.  Just increment this index each time, and wrap around when you get to the end of the array. -- djones