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TLvlGraph: Improve MinimizeCrossings. Switch pairs even if they have SwitchDiff=0

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A pair with "SwitchDiff=0" may block surrounding nodes from being switched. After switching, one of the changed neighbouring pairs may be able to reduce further crossings.

git-svn-id: trunk@60887 -
This commit is contained in:
martin 2019-04-07 19:52:05 +00:00
parent 4e2c794836
commit e9367141f8
1 changed files with 45 additions and 4 deletions
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49
components/lazcontrols/lvlgraphctrl.pas
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@ -698,7 +698,7 @@ type
constructor Create(aLevel: TMinXLevel; aIndex: integer);
destructor Destroy; override;
procedure UnbindFromSwitchList;
procedure BindToSwitchList;
function BindToSwitchList(AtEnd: Boolean=False): integer;
procedure ComputeCrossingCount(out Crossing, SwitchCrossing: integer);
function ComputeSwitchDiff: integer;
property SwitchDiff: integer read FSwitchDiff write SetSwitchDiff;
@ -1390,9 +1390,22 @@ begin
NextSameSwitchPair:=nil;
end;
procedure TMinXPair.BindToSwitchList;
function TMinXPair.BindToSwitchList(AtEnd: Boolean): integer;
var
n: TMinXPair;
begin
NextSameSwitchPair:=Graph.SameSwitchDiffPairs[Graph.SameSwitchDiffPair0+SwitchDiff];
Result := 0;
n:=Graph.SameSwitchDiffPairs[Graph.SameSwitchDiffPair0+SwitchDiff];
if AtEnd and (n<> nil) then begin
while n.NextSameSwitchPair <> nil do begin
n:=n.NextSameSwitchPair;
inc(Result);
end;
n.NextSameSwitchPair:=Self;
PrevSameSwitchPair:=n;
exit;
end;
NextSameSwitchPair:=n;
Graph.SameSwitchDiffPairs[Graph.SameSwitchDiffPair0+SwitchDiff]:=Self;
if NextSameSwitchPair<>nil then
NextSameSwitchPair.PrevSameSwitchPair:=Self;
@ -1650,15 +1663,43 @@ begin
end;
procedure TMinXGraph.SwitchCrossingPairs(MaxRun: int64; var Run: int64);
(* Calculating how many rounds to go for ZeroRun
Switching a node with SwitchDiff=0, can move other zero-nodes (i.e.,
remove them in one place, and create another in a new place)
Extra loops are needed to:
- run such new nodes
- re-run and switch back the original nodes, to test the zero-nodes
that were removed.
Sucessful swaps (unblocking actual crossings) can be found even at
high multiplies of LastInsertIdx (the count of zero-nodes)
*)
var
Pair: TMinXPair;
LastInsertIdx, ZeroRun: Integer;
begin
ZeroRun := 0;
while (MaxRun>0) and (BestCrossCount<>0) do begin
//debugln(['TMinXGraph.SwitchCrossingPairs ',MaxRun,' ',Run]);
Pair:=FindBestPair;
Run+=1;
if (Pair=nil) or (Pair.SwitchDiff=0) then exit;
if (Pair=nil) then exit;
if (Pair.SwitchDiff=0) then begin
dec(ZeroRun);
if ZeroRun = 0 then
exit;
end
else
ZeroRun := 0;
SwitchPair(Pair);
if (Pair.SwitchDiff=0) then begin
Pair.UnbindFromSwitchList;
LastInsertIdx := Pair.BindToSwitchList(True);
If ZeroRun = -1 then
if CrossCount < BestCrossCount + BestCrossCount div 8 then // add 12% to BestCrossCount
ZeroRun := 8 * LastInsertIdx+1 // closer to a new BestCrossCount, search harder
else
ZeroRun := 2 * LastInsertIdx+1;
end;
MaxRun-=1;
end;
end;