On 2021-08-25 18:15, Ben Rubinstein via use-livecode wrote:
I simplified it down to this (pointless) loop which just rebuilds a
table one line at a time:
local tNewTable
repeat for each line tRow in tWorkTable
put tRow & return after tNewTable
end repeat
with these results:
6.7.11 MacOS 8 seconds
6.7.11 Win32 7 seconds
9.6.3 MacOS 0 seconds
9.6.3 Win32 591 seconds
Using a buffer var should workaround the performance issue (which is
related to the windows heap manager not being very good at continually
re-extending a buffer):
on mouseUp
local tLine
repeat 256 times
put "*" after tLine
end repeat
local tTime
put the millisecs into tTime
local tBuffer
local tText
repeat 257000 times
put tLine & return after tBuffer
if the number of codeunits in tBuffer > 500000 then
put tBuffer after tText
delete codeunit 1 to -1 of tBuffer
end if
end repeat
put tBuffer after tText
answer (the number of codeunits in tText) & return & (the millisecs -
tTime)
end mouseUp
In the original loop, tNewTable is continually extended internally,
something which appears to cause O(n^2) performance on Windows.
In the revised loop, an intermediate buffer var is used which (after
first time getting 'full') will have a backing store of 500k ish -
meaning tText is extended much less often. (Playing with the value of
500000 up or down will affect the resulting speed - there will always be
a sweet spot).
On my Windows VM - the above loop (which generates about 68mb of text or
so, takes about 3s.
Hope this helps!
Mark.
P.S. This is an engine issue - we'll need to look into why there's such
a difference with 6.7 - as, I'm pretty sure I kept the rules about
extending buffers pretty much the same in string concatenation.
--
Mark Waddingham ~ m...@livecode.com ~ http://www.livecode.com/
LiveCode: Everyone can create apps
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