[DKF]: Sometimes you come across something that makes you think “wow!” Here's one such thing: comparing the flat out single threaded performance of [Tcl] and [Python]. The problem I was looking at was to compute the sum of all prime numbers less than ten million (there are quite a few of them!) and the limiting factor is an efficient method for generating all the primes in the range. I present here two implementations for doing this in the languages under consideration, based on code originally from http://code.activestate.com/recipes/117119/ by way of https://stackoverflow.com/questions/567222/simple-prime-generator-in-python%|%StackOverflow
*** Tcl ***
======tcl
proc sum_primes_to {n {i 1}} {
set total 0
incr n 0
for {set q [expr {$i + $i}]} {$q < $n} {incr q} {
if {![info exists d($q)]} {
incr total $q
lappend d([expr {$q*$q}]) $q
} else {
foreach p $d($q) {
lappend d([expr {$p + $q}]) $p
}
unset -nocomplain d($q)
}
}
return $total
}
puts [sum_primes_to 10000000]
======
*** Python ***
======none
def sum_primes_to(n):
total = 0
d = {}
q = 2
while q < n:
if q not in d:
total += q
d[q * q] = [q]
else:
for p in d[q]:
d.setdefault(p + q, []).append(p)
del d[q]
q += 1
return total
print(sum_primes_to(10000000))
======
So… comparing the performance (overall for the script, with `time`) on a single system with production-grade builds of both languages, I get this:
Tcl 8.6: 13.250s
<<br>>
Python 2.7: 20.369s
<<br>>
Python 3.5: 22.204s
<<br>>
Python 3.6: 13.874s
These are all production builds that I've built locally to be as fast as possible on my hardware. (Also, they all produce the correct result, `3203324994356`.)
----
gonwalf 2018.01.31: I tried the same code on python 3.5 and tcl 8.6.6 and 8.6.8 with different results:
Tcl 8.6.6: 10.07s
<<br>>
Python 3.5: 10,80s
<<br>>
on Intel(R) Core(TM) i5-3470 CPU @ 3.20GHz
and
Tcl 8.6.8: 8,53s
<<br>>
Python 3.5: 8,08s
<<br>>
on Intel(R) Xeon(R) CPU E5-1650 v3 @ 3.50GHz
Which compiler flags did you use for the Tcl build?
[DKF]: 04-Feb-2018: I used the builds of both Tcl and Python built by macports, all running on my laptop (on mains power). All should be in release as-much-optimisation-as-usually-reasonable mode, and with chunks of computation as large as this, the CPU should be scaled up pretty equally. (NB: The system Tcl build on OSX is actually very slow; they enable an option that adds close tracking of low-level metrics but at great performance overhead.) I've got additional experimental builds where I make the Tcl code quite a lot faster, but they're definitely not used by anyone else yet (and aren't yet correct, semantically).
<<categories>>Performance | Tcl | Python