[SOLVED] Improved CPU cache usage at packages/fcl-image/src/pixtools.pp

[lagprogramming]

packages/fcl-image/src/pixtools.pp has:

Code: Pascal  [Select][+][-]

1. procedure FillRectangleColor (Canv:TFPCustomCanvas; x1,y1, x2,y2:integer; const color:TFPColor);
2. var x,y : integer;
3. begin
4.   SortRect (x1,y1, x2,y2);
5.   with Canv do
6.     begin
7.     for x := x1 to x2 do
8.       for y := y1 to y2 do
9.         DrawPixel(x,y,color);
10.     end;
11. end;

Code: Pascal  [Select][+][-]

1. procedure FillRectangleImage (Canv:TFPCustomCanvas; x1,y1, x2,y2:integer; const Image:TFPCustomImage);
2. var x,y : integer;
3. begin
4.   with image do
5.     for x := x1 to x2 do
6.       for y := y1 to y2 do
7.         Canv.DrawPixel(x,y, colors[x mod width, y mod height]);
8. end;

Code: Pascal  [Select][+][-]

1. procedure FillRectangleImageRel (Canv:TFPCustomCanvas; x1,y1, x2,y2:integer; const Image:TFPCustomImage);
2. var x,y : integer;
3. begin
4.   with image do
5.     for x := x1 to x2 do
6.       for y := y1 to y2 do
7.         Canv.DrawPixel(x,y, colors[(x-x1) mod width, (y-y1) mod height]);
8. end;

The following patch improves CPU cache usage by switching the x and y loops.

Code: Pascal  [Select][+][-]

1. diff --git a/packages/fcl-image/src/pixtools.pp b/packages/fcl-image/src/pixtools.pp
2. index b8baccb5bb..da0fbfe700 100644
3. --- a/packages/fcl-image/src/pixtools.pp
4. +++ b/packages/fcl-image/src/pixtools.pp
5. @@ -73,8 +73,8 @@ procedure FillRectangleColor (Canv:TFPCustomCanvas; x1,y1, x2,y2:integer; const
6.    SortRect (x1,y1, x2,y2);
7.    with Canv do
8.      begin
9. -    for x := x1 to x2 do
10. -      for y := y1 to y2 do
11. +    for y := y1 to y2 do
12. +      for x := x1 to x2 do
13.          DrawPixel(x,y,color);
14.      end;
15.  end;
16. @@ -555,8 +555,8 @@ procedure FillRectangleImage (Canv:TFPCustomCanvas; x1,y1, x2,y2:integer; const
17.  var x,y : integer;
18.  begin
19.    with image do
20. -    for x := x1 to x2 do
21. -      for y := y1 to y2 do
22. +    for y := y1 to y2 do
23. +      for x := x1 to x2 do
24.          Canv.DrawPixel(x,y, colors[x mod width, y mod height]);
25.  end;
26.  
27. @@ -564,8 +564,8 @@ procedure FillRectangleImageRel (Canv:TFPCustomCanvas; x1,y1, x2,y2:integer; con
28.  var x,y : integer;
29.  begin
30.    with image do
31. -    for x := x1 to x2 do
32. -      for y := y1 to y2 do
33. +    for y := y1 to y2 do
34. +      for x := x1 to x2 do
35.          Canv.DrawPixel(x,y, colors[(x-x1) mod width, (y-y1) mod height]);
36.  end;

[AlexTP]

Posted to bugtracker,
https://gitlab.com/freepascal.org/fpc/source/-/issues/40242