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* Add some comments about used algorithms for increasing/decreasing list sizes

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git-svn-id: trunk@34861 -
This commit is contained in:
michael 2016-11-09 21:28:20 +00:00
parent d2ebb94fa3
commit 860ad25430
1 changed files with 10 additions and 2 deletions
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12
rtl/objpas/classes/lists.inc
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@ -144,10 +144,12 @@ begin
Error (SListIndexError, Index);
FCount := FCount-1;
System.Move (FList^[Index+1], FList^[Index], (FCount - Index) * SizeOf(Pointer));
// Shrink the list if appropriate
// Shrink the list if appropriate:
// If capacity>256 and the list is less than a quarter filled, shrink to 1/2 the size.
// Shr is used because it is faster than div.
if (FCapacity > 256) and (FCount < FCapacity shr 2) then
begin
FCapacity := FCapacity shr 1;
FCapacity := FCapacity shr 1;
ReallocMem(FList, SizeOf(Pointer) * FCapacity);
end;
end;
@ -175,6 +177,12 @@ var
IncSize : Longint;
begin
if FCount < FCapacity then exit(self);
{
For really big lists, (128Mb elements), increase with fixed amount: 16Mb elements (=1/8th of 128Mb).
For big lists (8mb elements), increase with 1/8th of the size
For moderate lists (128 or more, increase with 1/4th the size
For smaller sizes, increase with 16 or 4
}
if FCapacity > 128*1024*1024 then IncSize := 16*1024*1024
else if FCapacity > 8*1024*1024 then IncSize := FCapacity shr 3
else if FCapacity > 128 then IncSize := FCapacity shr 2