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Postings from April 2002
> -----Original Message----- > From: drieux [mailto:drieux@wetware.com] > Sent: Monday, April 29, 2002 4:51 PM > To: beginners@perl.org > Subject: Re: Scripts picks random elements from array , but it repeats > som etimes > > > > On Monday, April 29, 2002, at 01:03 , Bob Showalter wrote: > > > May I suggest a modification of the algorithm that avoids this > > problem: > > > > 1. generate a random index from 1 to (number of > remaining elements) > > 2. use the element at that index > > 3. move the last element into the index generated > > 4. decrement the number of remaining elements. > > My complements on a well written analysis of the core algorithm. > > My concern of course is that since this strategy is destructive > of the @array being searched, that one might find it slightly > faster to simply slice the array in flight.... > > http://www.wetware.com/drieux/CS/lang/Perl/Beginners/BenchMark s/randTest.txt splice() will be slower as the size of the array grows. If I take your benchmark and change to array from 1..100 to 1..10000, I get the following results for 100 iterations (on an old Pentium 266): Benchmark: timing 100 iterations of consume, decLoop... consume: 51 wallclock secs (50.72 usr + 0.03 sys = 50.75 CPU) @ 1.97/s (n=100) decLoop: 19 wallclock secs (19.45 usr + 0.01 sys = 19.46 CPU) @ 5.14/s (n=100)Thread Next