Subject: Millisecond timing

10. *****
 Q: How is millisecond timing done?

 A: A difficult task, but the facilities are readily available.
TurboPower Software's commercial Turbo Professional (don't confuse
with Borland's Turbo Professional) has a unit for this. (The usual
disclaimer applies). It is called tptimer and is part of the
ftp://garbo.uwasa.fi/pc/turbopas/bonus507.zip package. This one has
been released to the PD. I have also seen a SimTel upload
announcement of a ztimer11.zip for C and ASM, but I have no further
information on that. ftp://garbo.uwasa.fi/pc/turbopas/qwktimer.zip
is another option. It is not quite as accurate as tptimer.
   To test the tptimer unit in bonus507.zip you can use the
following example code
  uses Crt, tptimer;
  var time1, time2 : longint;
  begin
    InitializeTimer;
    time1 := ReadTimer;
    Delay (1356);    (* Or whatever code you wish to benchmark *)
    time2 := ReadTimer;
    RestoreTimer;
    writeln ('Elapsed = ', ElapsedTime (time1, time2)/1000.0 : 0 : 3);
  end.
   It is quite another question when you really need the millisecond
timing. The most common purpose for millisecond timing is testing
the efficiency of alternative procedures and functions, right? The
way I compare mine is simple. I call the procedures or functions I
want to compare for speed, say, a thousand times in a loop.  And
test this for elapsed time. This way the normal resolution (18.2
cycles per second) of the system clock becomes sufficient. This is
accurate enough for the comparisons.
     var elapsed : real; i : word;
     elapsed := TIMERFN;  (* e.g. from /pc/ts/tspa3455.zip *)
     for i := 1 to 1000 do YOURTEST;  (* Try out the alternatives *)
     elapsed := TIMERFN - elapsed;
     writeln ('Elapsed : ', elapsed : 0 : 2);
Incidentally, if you want to make more elaborate evaluations of the
efficiency of your code, Borland's Turbo Profiler is a useful tool.
(The usual disclaimer naturally applies.)
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