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Thanks a lot.
Could you explain this to Mats Bengtsson ?
PO
> -----Message d'origine-----
> De : Gary Yakhnes [mailto:gary@xxxxxxxxx]
> Envoye : mercredi 18 juillet 2001 17:12
> A : omega-list@xxxxxxxxxx
> Objet : RE: I think I have to change my opinion from bad
> precision to buggy c alculations
>
>
> Hello Pierre Orphelin,
>
> I must admit that you are absolutely correct here and I was wrong.
>
> Thanks for your post.
> Gary
>
>
> > > > > Hello Pierre Orphelin,
> > > > >
> > > > > Let's imagine for a moment that no such terrible things as
> > > > > "errors over bars", "double precision" and "epsilon" are exist.
> > > > > To do this let's look at the simple Indicator with Single
> > > > > precision, Single bar (lastbaronchart) and hopefully no
> "epsilon"
> > > > > (whatever it is):
> > > > >
> > > > > {########################################}
> > > > > If LastBarOnChart Then Begin
> > > > > Value1 = 10.3 - 10.2;
> > > > > Value2 = 10.2 - 10.1;
> > > > > If Value1 > Value2 Then Value3 = 1 Else Value3=0;
> > > > > plot1 (Value3);
> > > > > End;
> > > > > {########################################}
> > > > >
> >
> > Here is an other misunderstanding of Float 7 digits precision
> >
> > If LastBarOnChart Then Begin
> > Value1 = 10.3 - 10.2;
> > Value2 = 10.2 - 10.1;
> > If Value1 > Value2 Then Value3 = 1 Else Value3=0;
> > plot1 (Value3);
> > messagelog(value1:15:15,value2:15:15);
> > End;
> >
> > Produces:
> >
> > 0.100000000000000 //
> 0.099999400000000 //
> > Precision is impossible to determine // Precison is
> obviously 5
> > digits
> > ( 5 assumed, cannot be more)
> >
> > Is it a bug? NO.
> >
> > Value1 = 10.3 - 10.2 contains two numbers with 7 digits precision
> > 10.3 is stored as 10.30000xxxx
> > 10.2 is stored as 10.20000xxxx
> > where xxx is unknown to Float precision and will produce
> garbage after 7th
> > digit,
> >
> > When difference is calculated it is performed on 7 digit - 7 digits
> > BUT:
> > 10.y - 10.z will produce 00.[y-z]. -y=3, z=2
> > So the 2 digits are lost in the difference because 10 -10 =
> 00, and only
> > beacuqse of that.
> > What remains is 5 digit and is conform to the original initial Float
> > precision.
> >
> > There is no bug at all, only a special case where the
> difference of two very
> > close numbers remove the 2 digits to the left.
> >
> > The only solution is to have more than a float to store
> numbers, but even
> > a double will lose the 2 digits of the original double precision.
> > So this kind of operation will always lose precision in terms
> of digits, but
> > not in intriinsic precision ( the precision of the difference
> is ONE digit
> > in this case = 0.1)
> >
> > And again, the difference here is far beyond the THREE
> digits precision of
> > the original numbers.
> >
> > 'Cannot undestand why you focus on such stupid things that
> are only logic
> > and does not involve any form of bug.
> > You will have the same problem using C or anything you want
> with 7 digits
> > float precision.
> >
> > Sincerely,
> >
> > Pierre Orphelin
> > www.sirtrade.com
> > TradeStation Technologies representative in France
> >
> >
> >
> >
> >
> >
>
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