Great, results for `n=6`, `k=9` on my machine,
IteratorOfCartesianProduct Method : 452ms
Initial Mentioned Method : 203ms
Burkhard's Method : 047ms
Python : 066ms
Many thanks everyone,
Rob
________________________________________
From: Burkhard Höfling [burkh...@hoefling.name]
Sent: 17 January 2014 11:57
To: forum@mail.gap-system.org
Cc: Wolstenholme, Robert; Alexander Konovalov; Dmitrii Pasechnik
Subject: Re: [GAP Forum] Iteration Over Lists of Lists
Dear Robert,
>> Thanks, this is what I wanted.
>> However, I timed it this morning and found it to actually be slower than the
>> method I previously mentioned (currently speed is of significant importance
>> for what I'm doing). I've included the test script below. You can vary the
>> values of `n` (number of lists) and `k` (size of lists). Note for `n=6` and
>> `k=9` I am getting,
Iterators cause a lot of overhead per call. If you just modify your code a bit,
you should get close to Python speed with GAP. On my machine, I get
teratorOfCartesianProduct Method: 915 ms
Your Mentioned Method : 493 ms
variant below: : 125 ms
(didn’t try Python).
Cheers
Burkhard.
size_rc := List([1..n], x -> k);
base := List([1..n], x -> 1); #We store the iteration step state in base
a := 1;
start := Runtime();
stop := false;
repeat
#Perform whatever list[i][base[i]] calculations here
#a := a + 1;
#Print("Base: ", base, "\n");
#Execute the incrementor
base[1] := base[1] + 1;
j := 1;
while base[j] > size_rc[j] and j < n do
base[j] := 1;
j := j + 1;
base[j] := base[j] + 1;
od;
until j = n and base[n] > size_rc[n];
total2 := Runtime() - start;
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