an HP question...

[webmasterpdx]

I did some timing using TEVAL, and got some unusual results.
I used the following program:

Code:


EXPORT T1(V,N) // Using alternate to CASE
BEGIN
FOR I FROM 1 TO N DO
REPEAT
 IF (V==1) THEN C:=2; BREAK; END;
 IF (V==2) THEN C:=3; BREAK; END;
 IF (V==3) THEN C:=5; BREAK; END;
 IF (V==4) THEN C:=7; BREAK; END;
 C:=0; // DEFAULT
UNTIL 1; // REPEAT...ALWAYS
END; // FOR
END; // BEGIN

EXPORT T2(V,N) // Using CASE statement
BEGIN
FOR I FROM 1 TO N DO
CASE
 IF (V==1) THEN C:=2; END;
 IF (V==2) THEN C:=3; END;
 IF (V==3) THEN C:=5; END;
 IF (V==4) THEN C:=7; END;
DEFAULT:
 C:=0;
END; // CASE
END; // FOR
END; // BEGIN

EXPORT TEST(V,N) // Timing CASE Vs Alternative
BEGIN
LOCAL A,B;
A:=TEVAL(
T1(V,N)
); // TEVAL
B:=TEVAL(
T2(V,N)
);
RETURN {A,B,C};
END; // BEGIN

The results are:
TEST(1,1) gives {0_s,0.001_s,2}
This indicates the CASE alternative is faster on a single run, but...
TEST(1,1000) gives {0.086_s,0.069_s,2}
This indicates that with a loop of 1000 times, the CASE statement is faster????

In general, TEST(n,1000) indicates that the CASE statement is faster, even for when the DEFAULT is used.

I notice that TEVAL can give different values on successive runs. Why is that?

Also, why would the CASE alternative seem to give a faster run time than CASE for a run of 1, but as soon as N (the loop count) rises, typically with a value of 2, the CASE statement is faster????

Thanks
-Donald