For anyone who cares, I re-wrote Bob's code to handle a variable-length
string like so:
on mouseUp
put 10 into wc
repeat with i = 1 to wc
put i & space after tData
end repeat
put the ticks into line one of theTime
repeat 1000000 div wc
repeat with j = 1 to wc
put word j of tData into theWord
end repeat
end repeat
put the ticks into line 2 of theTime
repeat 1000000 div wc
repeat for each word theWord in tData
--get theWord
end repeat
end repeat
put the ticks into line 3 of theTime
put ("Example 1 took " & line 2 of theTime - line 1 of theTime) & "
ticks" into line 4 of theTime
put ("Example 2 took " & line 3 of theTime - line 2 of theTime) & "
ticks" into line 5 of theTime
put theTime into fld 1
end mouseUp
with that I get:
83548656597
83548656614
83548656619
Example 1 took 17 ticks
Example 2 took 5 ticks
with wc = 1000 I get:
83548666360
83548666715
83548666719
Example 1 took 355 ticks
Example 2 took 4 ticks
Note that the second example is getting faster because I'm shortening the
repeat count for longer
with wc = 100000 I had to change the outer repeat loop to execute only once
-- I got:
83548674504
83548678993
83548678994
Example 1 took 4489 ticks
Example 2 took 1 ticks
it's important to note that the first loop doesn't scale linearly with the
size of the input. The example with wc = 1000 executes the outer loop
1/100th as many times as the example with wc = 10, so to make the times
equivalent you'd multiply by 100 and get:
Example 1 took 35500 ticks
Example 2 took 400 ticks
So the second example *does* scale linearly -- 100x the size of the input =
roughly 100x the time: 400 ticks vs. 5 ticks. The first example -- 35500
vs. 17 -- that's nowhere near linear. And multiplying the size of the input
by 100 again in the third trial, if the outer loop had run as many times,
the performance would have been roughly
Example 1 took 448900000 ticks
Example 2 took 100000 ticks
Again, the second example scales roughly linearly and would finish in about
30 minutes, while the first example would take almost 3 months to finish.
On Fri, Feb 14, 2014 at 9:23 AM, Geoff Canyon <gcan...@gmail.com> wrote:
>
> > On Feb 13, 2014, at 11:12 PM, "J. Landman Gay" <jac...@hyperactivesw.com>
> wrote:
> >
> > It's pretty well established that the "for each" form is a magnitude
> faster than the counting form.
>
> Nitpicking, but "[order of] magnitude" doesn't come close to covering the
> efficiency. The example Bob gave, since there were only ten items in the
> line, dramatically *understates* the benefits of repeat for each, which
> scales with the length of the source. A 1,000 or 100,000 item source would
> show much more than a magnitude of improvement.
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