If ->at() works but ->sclr doesn't that would suggest a problem. What version of PDL are you running? Is it possible that @t_stats was initialized to piddle values for the slow case. at and sclr should give the same results....
--Chris On Thu, Feb 2, 2012 at 12:24 PM, Adam Russell <[email protected]> wrote: > Well, the docs > http://pdl.perl.org/PDLdocs/Core.html#sclr > state "The sclr method is useful to turn a piddle into a normal Perl > scalar." > If at works and sclr doesn't than maybe something is wrong with the sclr > code? > The docs say they should have the same output with the convenience that sclr > doesn't require you to specify a position. > So, lets see what happens when I use at... > Ok, I now see this in the profiler output > > @s_t_stats=sort {$b <=> $a} @t_stats; > # spent 3.92ms making 4 calls to CORE:sort, avg 980µs/call > So, ok, at wins! > Thanks for the advice! > Finally though, does this indicate a problem with sclr? > > ________________________________ > Date: Thu, 2 Feb 2012 10:31:53 -0600 > > Subject: Re: [Perldl] how to sort a piddle ??? > From: [email protected] > To: [email protected] > CC: [email protected] > > > Hmm, looks to me like "sclr" may not be doing what you mean. I'm not sure, > though, because I've never noticed sclr before. At any rate, it looks like > the sort is calling the spaceship operator on piddles, but it should be > using the built-in spaceship operator because it should be sorting scalars. > > What happens to your sort if you use "at" instead of "sclr"? > > David > > On Thu, Feb 2, 2012 at 10:01 AM, Adam Russell <[email protected]> wrote: > > This thread reminded me of a pdl sort issue I was having. > I hope I not too off topic... > So, I am using pdl from within a larger body of Perl code. > I am using PDL::Stats to perform a t_test on a bunch of data I store in > pdls. > Once I get done with this I sort the t-statistics and then throw away the > pdls. > I noticed my code was running somewhat slower than I would have thought it > shoud. > So, I ran the code under the NYT profiler. My code was spending the majority > of its time (~80% of total execution time!) > on the last line below(yeah, I uncreatively named the pdls "pdls"): > > foreach my $dim_n (0..$self->{dimension}-1){ > my ($t, $df) = t_test($pdls[$dim_n][$cat_n][0], > $pdls[$dim_n][$cat_n][1]); > $t_stats[$dim_n]=$t->abs->sclr; > } > @s_t_stats=sort {$b <=> $a} @t_stats; > > Here is what profiler output for that line looks like: > @s_t_stats=sort {$b <=> $a} @t_stats; > # spent 5.18s making 4 calls to CORE:sort, avg 1.29s/call > # spent 3.43s making 91451 calls to PDL::string, avg 38µs/call > # spent 939ms making 91451 calls to PDL::spaceship, avg 10µs/call > # spent 44µs making 15 calls to PDL::DESTROY, avg 3µs/call > > 1.29 seconds for each call to sort is very long time! From the calls made > when that line is executed it seems that for some reason > it is doing some sort of string conversion? But why? Surely $t->abs->sclr is > returning a numeric, right? > The code currently takes about 10 seconds to run. If I take care of this > sort problem I could probably get runs in > under 3 seconds. > > Any advice on why this sort is so slow? > Best Regards, > Adam > > >> Date: Thu, 2 Feb 2012 07:07:24 -0600 >> From: [email protected] >> To: [email protected] >> CC: [email protected] >> Subject: Re: [Perldl] how to sort a piddle ??? > >> >> I agree with Matt that you are probably looking for `qsort`. >> >> As to what >> >> @e = pdl(3,2,6,4,8,6); >> @r = sort{$a <=> $b} @e; >> >> is doing, its working perfectly; its just not doing what you mean. @e >> is a one element Perl-level array, its one element is a PDL object. >> Any sort on a one element array will return the same order, what else >> could it do. >> >> You have to remember that a PDL object is just another scalar in >> Perl's eyes, as are all objects. >> >> Here is another example >> >> @e = (pdl(3,2,6,4,8,6), pdl(5,6,2,1)); >> @r = sort{$a <=> $b} @e; >> >> Here @e has two PDL object. When you sort objects numerically ( using >> <=> ), what you will actually sort on is not their contents, but their >> address in memory. >> >> The take-away message is this: PDL overloads many of the Perl >> operators, and it can feel like PDL and Perl are fully integrated, but >> in truth a PDL object is still an object, that is a scalar reference >> with methods and overloads. PDL tries to Do What You Mean when it can, >> this is not one of those times. > > > _______________________________________________ > Perldl mailing list > [email protected] > http://mailman.jach.hawaii.edu/mailman/listinfo/perldl > > > > > -- > "Debugging is twice as hard as writing the code in the first place. > Therefore, if you write the code as cleverly as possible, you are, > by definition, not smart enough to debug it." -- Brian Kernighan > > > _______________________________________________ > Perldl mailing list > [email protected] > http://mailman.jach.hawaii.edu/mailman/listinfo/perldl > _______________________________________________ Perldl mailing list [email protected] http://mailman.jach.hawaii.edu/mailman/listinfo/perldl
