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Very interesting posts!...need time to digest the lot. The idea of using
function like abs(), prec() etc... sounds like a good one to go around that
problem.
-----Original Message-----
From: owner-metastock@xxxxxxxxxxxxx
[mailto:owner-metastock@xxxxxxxxxxxxx]On Behalf Of Lance Collins
Sent: Monday, 1 October 2001 8:50 PM
To: metastock@xxxxxxxxxxxxx
Subject: RE: Calculation error in MS
Allen wrote:
>An issue that also affects the database is that metastock stores data
>in the old microsoft basic 32 bit precission format. Upon loading that
>format get's converted to IEEE format single precission. We're probably
>loosing bits just in this conversion. That is then compounded by
>calculations being done in single precission.
The same number of bits are used for exponent and mantissa in both IEEE and
the old MS format so there is no loss of precision in the conversion.
There are 23 bits for the mantissa (approximately 6 significant decimal
digits) which is more than enough to hold raw data values of price or index
in the data files.
It is not easy to do extended calculations which avoid issues such as the
problem of subtraction of similar size quantities. These things can
produce nonsense results regardless of the precision available. Floating
point arithmetic also makes the use of tests for equality problematic.
The issue is not the use of single precision but the limitations of the
formula language provided with Metastock. Some of you seem to be pushing
the explorer way beyond it's capabilities. If Metastock used double
precision it would merely mean that it took a little longer to get into the
same problems.
What to do when you outgrow the explorer is another debate altogether.
Lance
p.s. I've always thought the financial world to be mesmerized by numbers
but it's not numerate.
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