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Optimize TDeque.IncreaseCapacity
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Author
Topic: Optimize TDeque.IncreaseCapacity (Read 7770 times)
Thaddy
Hero Member
Posts: 14382
Sensorship about opinions does not belong here.
Re: Optimize TDeque.IncreaseCapacity
«
Reply #15 on:
October 14, 2018, 08:06:38 pm »
Quote from: Alextp on October 14, 2018, 07:53:17 pm
What about my change?
The many branches in that code would make it slower than the current implementation.
Either use a look-up or stick to your original plan and increase the initial size to say, 4 or 5.
You have to devise some tests...
Logged
Object Pascal programmers should get rid of their "component fetish" especially with the non-visuals.
Artem3213212
New member
Posts: 7
Re: Optimize TDeque.IncreaseCapacity
«
Reply #16 on:
October 14, 2018, 08:45:12 pm »
Quote from: Alextp on October 14, 2018, 07:53:17 pm
What about my change?
Ok, but it make some bad work with memory pages. Correct version:
Code: Pascal
[Select]
[+]
[-]
procedure
TDeque
.
IncreaseCapacity
;
const
// if size is small, multiply by 2;
// if size bigger but <256M, inc by 1/8*size;
// otherwise inc by 1/16*size
cSizeSmall
=
1
*
1024
*
1024
;
cSizeBig
=
256
*
1024
*
1024
;
var
i
,
OldEnd
:
SizeUInt
;
DataSize
:
SizeUInt
;
begin
OldEnd
:
=
FCapacity
;
DataSize
:
=
FCapacity
*
SizeOf
(
T
)
;
if
FCapacity
=
0
then
FCapacity
:
=
4
else
if
DataSize<cSizeSmall
then
FCapacity
*=
2
else
if
DataSize<cSizeBig
then
FCapacity
+=
FCapacity
div
8
and
$FFFFF000
else
FCapacity
+=
FCapacity
div
16
and
$FFFFF000
;
SetLength
(
FData
,
FCapacity
)
;
if
(
FStart>
0
)
then
for
i
:
=
0
to
FStart
-
1
do
FData
[
OldEnd
+
i
]
:
=
FData
[
i
]
;
end
;
«
Last Edit: October 14, 2018, 08:55:41 pm by Artem3213212
»
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AlexTP
Hero Member
Posts: 2406
Re: Optimize TDeque.IncreaseCapacity
«
Reply #17 on:
October 14, 2018, 08:48:59 pm »
Thaddy,
branches are needed here, to check: n in one of ranges:
[0..1M] [1M..256M] [256M..inf]
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CudaText editor
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ASerge
Hero Member
Posts: 2249
Re: Optimize TDeque.IncreaseCapacity
«
Reply #18 on:
October 17, 2018, 09:29:25 pm »
I like TFPList.Expand
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Bart
Hero Member
Posts: 5290
Re: Optimize TDeque.IncreaseCapacity
«
Reply #19 on:
January 06, 2021, 12:57:17 pm »
These changes to TDeque have broken it.
If the array isn't doubled (in IncreaseCapacity) then it is not circular anymore (the calculation of the positions wehre to put/get values doesn't match anymore.
See
Issue #38306
.
Bart
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Optimize TDeque.IncreaseCapacity
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