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+ keep track of the pivot index in all quicksort implementations. No functional changes,

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but will be used to prevent overlap in the divided subregions and also infinite loops
  in case of an incorrect compare function.

git-svn-id: trunk@41222 -
This commit is contained in:
nickysn 2019-02-04 15:32:41 +00:00
parent b47c58dddc
commit 26486bbaea
1 changed files with 41 additions and 16 deletions
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57
rtl/inc/sortbase.pp
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@ -67,13 +67,14 @@ implementation
Procedure QuickSort_PtrList_NoContext(ItemPtrs: PPointer; L, R : Longint; Procedure QuickSort_PtrList_NoContext(ItemPtrs: PPointer; L, R : Longint;
Comparer: TListSortComparer_NoContext); Comparer: TListSortComparer_NoContext);
var var
I, J : Longint; I, J, PivotIdx : Longint;
P, Q : Pointer; P, Q : Pointer;
begin begin
repeat repeat
I := L; I := L;
J := R; J := R;
P := ItemPtrs[ (L + R) div 2 ]; PivotIdx := (L + R) div 2;
P := ItemPtrs[PivotIdx];
repeat repeat
while Comparer(P, ItemPtrs[i]) > 0 do while Comparer(P, ItemPtrs[i]) > 0 do
Inc(I); Inc(I);
@ -84,6 +85,10 @@ begin
Q := ItemPtrs[I]; Q := ItemPtrs[I];
ItemPtrs[I] := ItemPtrs[J]; ItemPtrs[I] := ItemPtrs[J];
ItemPtrs[J] := Q; ItemPtrs[J] := Q;
if PivotIdx = I then
PivotIdx := J
else if PivotIdx = J then
PivotIdx := I;
Inc(I); Inc(I);
Dec(J); Dec(J);
end; end;
@ -117,13 +122,14 @@ procedure QuickSort_PtrList_Context(ItemPtrs: PPointer; ItemCount: SizeUInt; Com
procedure QuickSort(L, R : Longint); procedure QuickSort(L, R : Longint);
var var
I, J : Longint; I, J, PivotIdx : Longint;
P, Q : Pointer; P, Q : Pointer;
begin begin
repeat repeat
I := L; I := L;
J := R; J := R;
P := ItemPtrs[ (L + R) div 2 ]; PivotIdx := (L + R) div 2;
P := ItemPtrs[PivotIdx];
repeat repeat
while Comparer(P, ItemPtrs[I], Context) > 0 do while Comparer(P, ItemPtrs[I], Context) > 0 do
Inc(I); Inc(I);
@ -134,6 +140,11 @@ procedure QuickSort_PtrList_Context(ItemPtrs: PPointer; ItemCount: SizeUInt; Com
Q := ItemPtrs[I]; Q := ItemPtrs[I];
ItemPtrs[I] := ItemPtrs[J]; ItemPtrs[I] := ItemPtrs[J];
ItemPtrs[J] := Q; ItemPtrs[J] := Q;
if PivotIdx = I then
PivotIdx := J
else if PivotIdx = J then
PivotIdx := I;
Inc(I); Inc(I);
Dec(J); Dec(J);
end; end;
@ -169,13 +180,14 @@ var
procedure QuickSort(L, R : Longint); procedure QuickSort(L, R : Longint);
var var
I, J : Longint; I, J, PivotIdx : Longint;
P : Pointer; P : Pointer;
begin begin
repeat repeat
I := L; I := L;
J := R; J := R;
P := Items + ItemSize*((L + R) div 2); PivotIdx := (L + R) div 2;
P := Items + ItemSize*PivotIdx;
repeat repeat
while Comparer(P, Items + ItemSize*I, Context) > 0 do while Comparer(P, Items + ItemSize*I, Context) > 0 do
Inc(I); Inc(I);
@ -188,10 +200,16 @@ var
Move((Items + ItemSize*I)^, TempBuf^, ItemSize); Move((Items + ItemSize*I)^, TempBuf^, ItemSize);
Move((Items + ItemSize*J)^, (Items + ItemSize*I)^, ItemSize); Move((Items + ItemSize*J)^, (Items + ItemSize*I)^, ItemSize);
Move(TempBuf^, (Items + ItemSize*J)^, ItemSize); Move(TempBuf^, (Items + ItemSize*J)^, ItemSize);
if P = (Items + ItemSize*I) then if PivotIdx = I then
P := Items + ItemSize*J begin
else if P = (Items + ItemSize*J) then PivotIdx := J;
P := Items + ItemSize*I; P := Items + ItemSize*PivotIdx
end
else if PivotIdx = J then
begin
PivotIdx := I;
P := Items + ItemSize*PivotIdx;
end;
end; end;
Inc(I); Inc(I);
Dec(J); Dec(J);
@ -232,13 +250,14 @@ procedure QuickSort_ItemList_CustomItemExchanger_Context(
procedure QuickSort(L, R : Longint); procedure QuickSort(L, R : Longint);
var var
I, J : Longint; I, J, PivotIdx : Longint;
P : Pointer; P : Pointer;
begin begin
repeat repeat
I := L; I := L;
J := R; J := R;
P := Items + ItemSize*((L + R) div 2); PivotIdx := (L + R) div 2;
P := Items + ItemSize*PivotIdx;
repeat repeat
while Comparer(P, Items + ItemSize*I, Context) > 0 do while Comparer(P, Items + ItemSize*I, Context) > 0 do
Inc(I); Inc(I);
@ -249,10 +268,16 @@ procedure QuickSort_ItemList_CustomItemExchanger_Context(
if I < J then if I < J then
begin begin
Exchanger(Items + ItemSize*I, Items + ItemSize*J, Context); Exchanger(Items + ItemSize*I, Items + ItemSize*J, Context);
if P = (Items + ItemSize*I) then if PivotIdx = I then
P := Items + ItemSize*J begin
else if P = (Items + ItemSize*J) then PivotIdx := J;
P := Items + ItemSize*I; P := Items + ItemSize*PivotIdx
end
else if PivotIdx = J then
begin
PivotIdx := I;
P := Items + ItemSize*PivotIdx;
end;
end; end;
Inc(I); Inc(I);
Dec(J); Dec(J);