Re: [boost] [fixed_point] Request for interest in a binary fixed point library

Subject: Re: [boost] [fixed_point] Request for interest in a binary fixed point library
From: Vicente J. Botet Escriba (vicente.botet_at_[hidden])
Date: 2012-04-10 16:55:35

Le 10/04/12 19:46, Andrii Sydorchuk a écrit :
>> the recent discussion on the MultiplePrecission Arithmetic library has
>> show that some people has its ow fixed point library.
>
> Could you explain a bit your idea? By fixed point library do you mean fixed
> floating-point types (e.g. 1024-bit double)?
>
>
Hi,

No. I meant really a fixed, not a floating -point, in which the 
fractional part is fixed not variable. C++/Boost Chrono is designed in 
some way as a fixed point time unit, limited to the use of  intmax_t 
type as underlying (which is enough to represent the time we want to 
represent). My current needs are for small fixed-point, not for 
arbitrary large fixed-point numbers, so I'll need less than word-bits 
fractional numbers.

You can take a look at 
http://en.wikipedia.org/wiki/Fixed-point_arithmetic. This will give you 
the context. This C++ proposal 
(http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3352.html)  is 
quite in line of the design I'm locking for.

The domain is quite related to the quantization (see 
http://en.wikipedia.org/wiki/Quantization_%28signal_processing%29 for a 
brief overview) where fixed-point is a way of uniform quantization. For 
the applications I'm working on now, I will need also non-uniform 
quantizations, as the ones provided by the reverse of a monotonic 
function or lookup-tables, but this is out of the scope of a fixed-point 
library.

The questions on my initial post are some of the ones we need to answer 
when designing such a library.

Hope this clarifies the intent,
Vicente