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From: Andy Little (andy_at_[hidden])
Date: 2005-09-25 09:18:18

"Peder Holt" <peder.holt_at_[hidden]> wrote in message
> What should we do about the accuracy of double_ operations?
> The implementation of plus,minus,times and divide mimics the behaviour
> of the runtime equivalent, double. This means that the mantissa is
> trunkated from 61 to 52 bit for every fundamental operation. The
> result of this, is that complex functions such as sine and exponential
> will differ from their runtime counterpart, unless a specialization is
> made for double_. The problem would disappear if we allow calculations
> with double_ to be more accurate than calculations with double. Is
> this a problem?

 There is neverending discussion on comp.lang.c++.mod regarding differences
between runtime floats on various platforms. IMO this is an ideal opportunity to
create a platform independent floating point type, IOW one with an exact length
of mantissa and exponent specified and with a consistent policy on rounding
etc. I think this is how it is done in Java though the only link I can find
Other question is ... What sort of rounding do you use?
Also ... I'm assuming it is simple enough to program the length of mantissa and
exponent?. By making them length adjustable you would be able to regain
platform dependence via typedefs where required. thus providing the best of both

Andy Little

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