You have to stop spending so much time playing with all this bogus benchmarking :)
It not bogus :) Its an example to find the best method for a project.
If you prefer I'll ask the question I was trying to answer with the benchmark:
Assuming you have an array of 0-15 elements is it quicker/more efficient to:
1) create a hash slice and use exists when checking for specific ones or 2) grep a regex out of the array when checking for specific ones
slice: use strict; use warnings; my @k=qw(1 2 3 4 5 6); my %n;@[EMAIL PROTECTED] = @k; print "hi" if exists $n{1}; print "hi" if exists $n{3}; print "hi" if exists $n{5}; print "hi" if exists $n{7}; print "hi" if exists $n{9}; print "hi" if exists $n{11};
grep: use strict; use warnings; my @k=qw(1 2 3 4 5 6); print "hi" if grep /^1$/, @k; print "hi" if grep /^3$/, @k; print "hi" if grep /^5$/, @k; print "hi" if grep /^7$/, @k; print "hi" if grep /^9$/, @k; print "hi" if grep /^11$/, @k;
Benchmark: timing 5000000 iterations of grep, slice...
grep: 3.65945 wallclock secs ( 2.33 usr + 0.04 sys = 2.37 CPU) @ 2109704.64/s (n=5000000)
slice: 2.37966 wallclock secs ( 2.52 usr + -0.01 sys = 2.51 CPU) @ 1992031.87/s (n=5000000)
Rate slice grep
slice 1992032/s -- -6%
grep 2109705/s 6% --
I would've thought the "slice and then use exists" would have been faster then "greping the entire array each time and using regexes" when you check it. but its consistently faster by an average 6-10%
Any ideas why that might be?
Well, first -- you're creating the hash inside the benchmark loop, which is not particularly light-weight.
Good point,
although in the real world app I'll have an array already so I want to see if its quicker to:
- make the hash via a slice and use exists
or
- just grep the whole array each time with a regex
If I use
my %hash = qw(1..20000);
and exists
vs.
my @array = qw(1..10000);
IE - no slice
then exists is a bit faster 2% or so, the problem is I start with an array I have no control over.
So, I'd have to do a slice to get the hash (or loop through it or otherwise do something to get the hash)
Second: You're using pathologically small lists. Try running it with 10,000 elements instead of ten.
that makes them about even, with slice being 1% faster at times, however the size of the array in the real world app are similar to the original benchmark
Third: Premature optimization is a terrible thing.
Premature? Could you elaborate?
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