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**Mel Bishop** · 21 Jan 2009, 02:12 PM

After modifying to cc404, I tried your code otherwise as-is. Same results.

Replaced FORMAT$ with USING$ and still got the same results. Hmmmmm.....

Don't have a clue.

**Brian Chirgwin** · 21 Jan 2009, 02:27 PM

#Register None

Alan,

Add

Code:

#Register None

This can go in the function GetChiPValue or at the top of the app.

Originally posted by Alan Vella View Post

Hi all,

If I compile and execute the above code, the message box pops up with the (wrong) answer 0.000000000000000100000001686.

If I compile and DEBUG the above code and then run it in debug mode I get a different (!) answer (the right one): 0.100008508707700254000000000.

Am I the only one whose getting this kind of behaviour?

Cheers,

Alan.

**Alan Vella** · 21 Jan 2009, 02:28 PM

OK, now if I add another procedure like this:

Code:

#COMPILE EXE
#DIM ALL


SUB myProc(BYVAL str AS STRING)
    MSGBOX str
END SUB


FUNCTION GetChiPValue(BYVAL X AS EXT, BYVAL F AS EXT) AS EXT
'
' FUNCTION PCHI2 - CALCULATES THE P-VALUE FROM
' THE CHI-SQUARE VALUE AND THE DEGREES OF FREEDOM
' The probability is calculated using series expansion 26.4.6. For the
' gamma functions 6.1.12, 6.1.8 and 6.1.1 are used.
' In: Handbook of mathematical Functions. Editors: Abramowitz M & Stegun IA,
' Dover, New York, 1972.
' Original code by Erik Christensen
        LOCAL D##,E##,R##,G##,H##,SL##,S##,T##,P##,C##,SK##,Q##
        Q = 1
        IF X = 0 OR F = 0 THEN GOTO 26
        D = F : E = D / 2 : R = F - INT(F / 2) * 2
        G = 1
        IF R > .3 THEN GOTO 20
    19  E = E - 1
        IF E < 1.8 THEN GOTO 22
        G = G * E : GOTO 19
    20  G = SQR(ATN(1) * 4) ' = PI
    21  E = E - 1
        IF E < .3 THEN GOTO 22
        G = G * E: GOTO 21
    22  H = ((X / 2) ^ (D / 2) * EXP(-X / 2)) / (X * G)
        SL = H * 2 * X / D : S = 0 : T = 0 : P = 1
    23  D = D + 2 : P = P * X / D : S = S + P : C = ABS(S - T)
        IF C < 1E-16 THEN GOTO 24
        T = S : GOTO 23
    24  SK = (S + 1) * SL : Q = 1 - SK
    25  IF Q < 1E-16 THEN Q = 1E-16
        myProc(STR$(q))
    26  FUNCTION = Q

END FUNCTION


FUNCTION PBMAIN () AS LONG
    LOCAL xxx AS EXT
    xxx = GetChiPValue(4.605, 2)
    MSGBOX( FORMAT$( xxx, "0.000000000000000000000000000" ) )
END FUNCTION

Running the above will give you the write answer in the two message boxes (the one in myProc and the one in pbMain).

If however I comment the line

Code:

myProc(STR$(q))

in myProc and re-run it I get the different answer in the message box from pbMain.

I've using PB for the past two years for my PhD research work and I've seen this behaviour before. Would appreciate it alot if someone could shed some light on this.

**Walt Thompson** · 21 Jan 2009, 04:19 PM

Solution

Hi Alan;

The problem with your second example is LOCAL variables are cleared when the function or sub they reside in are exited.

The solution is to declare the variables as STATIC, STATIC variables are not cleared when a sub or function is exited.

Code:

'Change this:
LOCAL D##,E##,R##,G##,H##,SL##,S##,T##,P##,C##,SK##,Q##

'To this:
STATIC D##,E##,R##,G##,H##,SL##,S##,T##,P##,C##,SK##,Q##

**Conrad Hoffman** · 21 Jan 2009, 09:20 PM

The OPs code is very typical of things I do. Though I haven't seen any weirdness recently, I may have had a similar problem in the past. I'd really like to know what's going on so I can avoid it, assuming it's some easily understood construct. I'd love to see a comment by PB staff, who understand what's going on under the hood.

**Bob Zale** · 22 Jan 2009, 02:07 AM

Good catch, Alan. Thanks for reporting it. Actually, this is a very rare issue which seems to have been around for many years. But it occurred so infrequently that we've never had a report.

For those who may be interested in the specific circumstances, here's how the planets aligned to cause it: Your line 22 with the EXP() function is the culprit. PowerBASIC is very good at rearranging an expression to simplify it and minimize the number of temporary values stored... but some are alway needed. At the EXP(), there are 2 temps plus the argument to EXP(). That makes 3. The EXP() function needs 2 more, and then there are 4 register variables for a total of nine. Unfortunately, the FPU has just eight registers, not nine, and it overflows at run-time The compiler should have generated an error during compilation, but its internal data showed that EXP() needed 1 temp, not 2. We've corrected it now, and it will be just fine in the next PBWIN 9.01 update. Yes, very soon.

For now, you can simplify the noted expression, or add a #REGISTER NONE directive to disable allocation of register variables. Sorry you had a problem.

Best regards,

Bob Zale
PowerBASIC Inc.

**Alan Vella** · 22 Jan 2009, 07:34 AM

Thanks all for your super-quick replies.

I think I'll just include the #REGISTER NONE at the top of my code and register the variables manually.

While we're on the the topic of registered variables I have one quick question: If I register two integer variables in a procedure A, then call procedure B from procedure A and register another two integer variables in procedure B ... will they not be registered since I have already used my maximum of two integer register variables in procedure A?

**Kev Peel** · 22 Jan 2009, 07:39 AM

From PB/WIN 9 Help:

Register variables are always local to the procedure where they appear.

Basically you get a brand new set of registers for each call to a procedure, excluding the 3 (IIRC) registers used internally by PowerBASIC.

**Conrad Hoffman** · 22 Jan 2009, 02:19 PM

Thanks Bob! I fooled with that example for quite a while before giving up. FWIW, I went back to some very old code I remembered having a similar problem with. As usual, no problem with PB and no use of EXP, I did however find a plain old programmers typo I never noticed before.

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