Compares Case Vs If

by: G.E. Ozz Nixon Jr.
Published: August 2009
Copyright 2009 by Friends of FPC

A few years ago, I redesigned my socket suite (DXSock) to use CASE statements versus if statements everywhere I could. Now, I am migrating everything to cross platform, Windows, Linux and Mac OS X - I decided to present a test and it's results for all to see.

Uses
   dxutil_environment;// contains TimeCounter for Windows, Linux and Mac

Var
   Loop:LongWord;
   StartTime:Comp;
   X,Y:Integer;

Begin
   X:=3;
   Y:=0;
   StartTime:=Trunc(TimeCounter);
   For Loop:=1 to 100000000 do begin
      If X=1 then begin
         Y:=X;
      end
      else if X=3 then begin
         Y:=X+3;
      end;
   end;
   System.Writeln(Trunc(Trunc(TimeCounter)-StartTime));

   X:=3;
   Y:=0;
   StartTime:=Trunc(TimeCounter);
   For Loop:=1 to 100000000 do begin
      Case X of
         1:Begin
            Y:=X;
         End;
         3:Begin
            Y:=X+3;
         End;
      End;
   end;
   System.Writeln(Trunc(Trunc(TimeCounter)-StartTime));

end.

On my MacBook Pro, the "if" logic took 444ms for 100 million iterations, while the case statement only took 352ms for 100 million iterations. Yet, the same code compiled and ran on this Linux web server took 593ms for the "if" logic and 664ms for the case statement. So, I added another "else if" and element to the case statement and then the case statement was faster by 80ms. So, when you have "deeper" if statements, case will be faster, however... apply logic to your code, if the first comparison of the if is what your code will hive the majority of the time, then definitely use if else/if.

G.E. Ozz Nixon Jr.

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