I went back to your original code and tried to run it. I am not able to
get it to return a value of 1, ever. It is the first time that I tried
it.... I do see the error in my code, now that you point it out, however
<blush>. Realize, however, that I am running this on a Linux box rather
than a Windows box. First, I was trying using the latest dev build. I
could NOT get it to return a value of 1, so I switched to the 1.1.4
release. I still can not cause it to happen.
Here is the code that determines the random numbers....
RTLFUNC(Rnd)
{
if ( rPar.Count() > 2 )
StarBASIC::Error( SbERR_BAD_ARGUMENT );
else
{
double nRand = (double)rand();
nRand = ( nRand / (double)RAND_MAX );
rPar.Get(0)->PutDouble( nRand );
}
}
Fine, so the return value depends on the compiler, because it is using
the built-in rand() method. RAND_MAX is a system dependent number
located in stdlib.h. rand() returns a random integer between 0 and
RAND_MAX.
(double) rand() / RAND_MAX has a result in the range of 0 to 1,
inclusive. One more time, the value 1.0 is included in the result set.
To exclude 1.0 from the result set, use (double) rand() / (RAND_MAX +
1.0 ), which excludes 1.0 from the result set. Of course, should 1.0 be
exluded or should it not? I think that what you want is an enhancement,
not a bug fix.
Johnny Andersson wrote:
Hi!
I always bought that one until I tried it myself. The reason why 1.0
never occurs in your modification of my code, is that you modified a
> to a <...
My code:
If Value>0.99999 Then
Count1=Count1+1
If Value=1 Then
Count2=Count2+1
Endif
EndIf
Your code:
If Value<0.99999 Then
Count1=Count1+1
If Value=one Then
Count2=Count2+1
Endif
EndIf
The inner IF statement (If Value=one Then...) will never be executed
since Value can never be 1.0 if Value<0.99999...
I corrected the < to a > and executed it again. The result was:
"Rnd>0.99999 occured 22 times, Rnd=1 occured 22 times. This was
calculated in 130 s."
So still, no values between 0.99999 and 1.0 occured since all 22
times when Rnd>0.99999, Rnd was 1.000000...
Sorry for being such an annoying person...
Best regards
Johnny
Andrew Douglas Pitonyak <[EMAIL PROTECTED]> skrev den Fri, 20 May
2005 15:51:55 -0400:
I changed your code and recieved a very different answer. Consider
the following:
Sub RndTest0
Dim i As Long
Dim Count1 As Long, Count2 As Long
Dim Value As Double
Dim one As Double
Dim ExecTime As Long
one = 1.0
ExecTime=Timer
Randomize
For i=1 To 1000000
Value=Rnd
If Value<0.99999 Then
Count1=Count1+1
If Value=one Then
Count2=Count2+1
Endif
EndIf
Next i
ExecTime=Timer-ExecTime
Print "Rnd>0.99999 occured "+Count1+ _
" times, Rnd=1 occured "+Count2+ _
" times. This was calculated in "+ExecTime+" s."
End Sub
Note: I used type Long rather than Integer to avoid round off.
Second, I did not compare to "1", which is an integer, but rather, I
stored 1.0 in a variable and compared to that. I could have also
compared against "1.0". This version NEVER returns a value of 1.0.
Johnny Andersson wrote:
I found that the Rnd function returns values (0.00000... to
1.00000...), not (0.00000... to 0.99999...), which would be better
in most cases.
Example:
Dim MyInteger As Integer
Dim MyArray(1 To 6) As Integer
Randomize
MyInteger=Int(6*Rnd)+1 'Supposed to return numbers 1 to 6, byt may
now and then return 7. Happened to me many times.
MyArray(MyInteger)=MyArray(MyInteger)+1 'Causes an error message
if MyInteger>6 which may happen in this case.
In this example Rnd returns 1.
Sub RndTest
Randomize 30091
Print Rnd
End Sub
This example took about 2 minutes to run on my PC (450 MHz P2, a
few other applications were running at the same time):
Sub RndTest0
Dim i As Long
Dim Count1 As Integer, Count2 As Integer
Dim Value As Double
Dim ExecTime As Long
ExecTime=Timer
Randomize
For i=1 To 1000000
Value=Rnd
If Value>0.99999 Then
Count1=Count1+1
If Value=1 Then
Count2=Count2+1
Endif
EndIf
Next i
ExecTime=Timer-ExecTime
Print "Rnd>0.99999 occured "+Count1+" times, Rnd=1 occured
"+Count2+" times. This was calculated in "+ExecTime+" s."
End Sub
It seems like every time Rnd>0.99999 then Rnd=1, so even though
Rnd produces 15 decimals it seems like only 5 (or less) are
relevant. When I tried Rnd=1 at 20 to 34 occasions (different
result different times of course) which indicates that Rnd=1 about
once every 29000 to 50000 times.
Anyway, is Rnd=1 supposed to ever happen or is this a bug?
---------------------------------------------------------------------
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
--
Andrew Pitonyak
My Macro Document: http://www.pitonyak.org/AndrewMacro.sxw
My Macro Book: http://www.hentzenwerke.com/catalog/oome.htm
Free Info: http://www.pitonyak.org/oo.php
---------------------------------------------------------------------
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
