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Subject: Re: [boost] RFC: Multiprecision arithmetic library
From: Andrii Sydorchuk (sydorchuk.andriy_at_[hidden])
Date: 2012-01-03 11:23:01

To make it portable (MSVC doesn't support neither __float128, nor 80-bit
long double).

On Tue, Jan 3, 2012 at 1:02 PM, Mathias Gaunard <
mathias.gaunard_at_[hidden]> wrote:

> On 12/26/2011 04:00 PM, Andrii Sydorchuk wrote:
>>> I like that idea. We have also been implementing our own floating point
>>> numbers with a base of 10, because of requirements in the financial
>>> business. I think it should be feasible to write a general wrapper for
>>> floating point numbers with an arbitrary base as well. Taking all that
>>> together we could have e.g. floating point numbers to a base of 77 with
>>> five byte mantissa and 42 bytes exponent, if needed anywhere.
>> While I agree that this functionality is useful especially for financial
>> problems, but it is probably not a good idea to try to unify it with
>> problem I mentioned.
>> Implementation of extended exponent wrapper around double/float types
>> could
>> be very efficient. As in most cases it uses native double operators (e.g.
>> +,-,*,/,sqrt) plus
>> some additional magic with exponent bits which are stored in int64 for
>> double (or int32 for float). It also satisfies IEEE 754 standard
>> requirement for rounding of the result of next operations
>> +,-,*,/,sqrt without any additional overhead.
> Why not use the built-in quadruple precision support of the compiler?
> GCC, for example, has a __float128 type that implements the IEEE754
> binary128 format.
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