From: Ray Andrews <rayandrews@eastlink.ca>
To: Zsh Users <zsh-users@zsh.org>
Subject: run time of math problem
Date: Fri, 19 Mar 2021 16:18:13 -0700 [thread overview]
Message-ID: <a1c6d13a-7a04-fba4-4419-7eccbf013824@eastlink.ca> (raw)
This question might not even be answerable and it's only a point of
interest:
I was working out some probabilities and the algorithm looks like this:
for ((level=1; level<100; level++)); do
sum=
remainder=$(( (level - 1.0) / level ))
for ((terms=level; terms; terms--)); do
sum+=$(( remainder**(terms - 1) ))
done
divided=$(( sum * (1.0 / level) ))
echo for level: $level, survival: $divided
done
Now if I avoid the 'remainder' variable:
for ((level=1; level<100; level++)); do
sum=
for ((terms=level; terms; terms--)); do
# 'remainder' calculation done directly here:
sum+=$(( ( (level - 1.0) / level )**(terms - 1) ))
done
divided=$(( sum * (1.0 / level) ))
echo for level: $level, survival: $divided
done
... I'd expect the thing to run a teeny bit faster but in fact it
runs about 15% slower. Is that explicable? Does zsh prefer
calculations done in steps with variables for each step? Or is this
just some little anomaly? Things might not optimize every time.
next reply other threads:[~2021-03-19 23:18 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-19 23:18 Ray Andrews [this message]
2021-03-19 23:46 ` Lawrence Velázquez
2021-03-19 23:51 ` Ray Andrews
2021-03-19 23:52 ` Oliver Kiddle
2021-03-20 2:40 ` Ray Andrews
2021-03-20 3:59 ` Lawrence Velázquez
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