New fpprec default value (Was Re: Precision of float and bfloat)

One option on former DEC VAX computers for technical computing was
'quadruple' precision, which required -- according to my limited
understanding -- four 32-bit words for each such value with up to 32
decimal digits.  If the standard precision of a 'float' be ~15 decimal
digits, then it seems reasonable that about double that precision might
be the default, although the option of setting the precision to greater
or lesser extents would presumably remain.  By analogy with 16 decimal
digits that might be standard with a 64-bit processor, doubling that 
amount for default extended precision would seem likely to be a useful
choice, extending significantly the precision but permitting perhaps
optimal use of the processor in implementing this with software.  Does
the IEEE standard involving 80 bits and hence about 20 decimal digits
have any bearing on this issue?
     JFO

On Mon, 26 Oct 2009, Stavros Macrakis wrote:

> Could you make your argument more explicit, please?  Yes, the default 64-bit
> floats are 15+ decimal digits; why does that imply that 32 decimal digits
> are the appropriate number for fpprec?  Because that is double the number of
> decimal digits?
>
>            -s
>
> On Mon, Oct 26, 2009 at 3:04 PM, John Ogilvie <ogilvie at cecm.sfu.ca> wrote:
>
>> As the precision of ordinary floating point seems to be 14 - 16 decimal
>> digits, and as many processors now have 64-bit logic as standard, perhaps
>> 32 decimal digits should be default for 'fpprec'.  One could presumably
>> set the precision to be less that 32 decimal digits if desired.
>>     J. F. Ogilvie
>>
>> On Mon, 26 Oct 2009, Robert Dodier wrote:
>>
>>  On Mon, Oct 26, 2009 at 9:52 AM, Raymond Toy <raymond.toy at stericsson.com>
>>> wrote:
>>>
>>>  I agree.  I think we should change the default value of fpprec to be
>>>> more than 16.  32 is a decent choice.  Or if that's too many, perhaps 24
>>>> or 25 digits.
>>>>
>>>
>>> 24 seems OK to me. I don't have a strong opinion about it.
>>>
>>> best
>>>
>>> Robert Dodier
>>>
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>