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 StackOverflow
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]
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
Python 2.7: 20.369s
Python 3.5: 22.204s
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
Python 3.5: 10,80s
on Intel(R) Core(TM) i5-3470 CPU @ 3.20GHz
and
Tcl 8.6.8: 8,53s
Python 3.5: 8,08s
on Intel(R) Xeon(R) CPU E5-1650 v3 @ 3.50GHz
Which compiler flags did you use for the Tcl build?