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* select the middle element in the default quicksort implementation in a way

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that doesn't generate arithmetic overflow for very large arrays

git-svn-id: trunk@41241 -
This commit is contained in:
nickysn 2019-02-06 18:05:48 +00:00
parent e467d2387d
commit 00a67caa40
1 changed files with 4 additions and 4 deletions
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8
rtl/inc/sortbase.pp
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@ -94,7 +94,7 @@ begin
repeat
I := L;
J := R;
PivotIdx := (L + R) div 2;
PivotIdx := L + ((R - L) shr 1); { same as ((L + R) div 2), but without the possibility of overflow }
P := ItemPtrs[PivotIdx];
repeat
while (I < PivotIdx) and (Comparer(P, ItemPtrs[i]) > 0) do
@ -161,7 +161,7 @@ procedure QuickSort_PtrList_Context(ItemPtrs: PPointer; ItemCount: SizeUInt; Com
repeat
I := L;
J := R;
PivotIdx := (L + R) div 2;
PivotIdx := L + ((R - L) shr 1); { same as ((L + R) div 2), but without the possibility of overflow }
P := ItemPtrs[PivotIdx];
repeat
while (I < PivotIdx) and (Comparer(P, ItemPtrs[I], Context) > 0) do
@ -230,7 +230,7 @@ var
repeat
I := L;
J := R;
PivotIdx := (L + R) div 2;
PivotIdx := L + ((R - L) shr 1); { same as ((L + R) div 2), but without the possibility of overflow }
P := Items + ItemSize*PivotIdx;
repeat
while (I < PivotIdx) and (Comparer(P, Items + ItemSize*I, Context) > 0) do
@ -308,7 +308,7 @@ procedure QuickSort_ItemList_CustomItemExchanger_Context(
repeat
I := L;
J := R;
PivotIdx := (L + R) div 2;
PivotIdx := L + ((R - L) shr 1); { same as ((L + R) div 2), but without the possibility of overflow }
P := Items + ItemSize*PivotIdx;
repeat
while (I < PivotIdx) and (Comparer(P, Items + ItemSize*I, Context) > 0) do