Re: Getting greatest decimal accuracy out of G_PI

[zentara <zentara1 sbcglobal net>]

On Fri, 02 Feb 2007 22:29:09 +0000
Ed Catmur <ed catmur co uk> wrote:

>On Fri, 2007-02-02 at 16:30 -0500, zentara wrote:
>> Please pardon my basic questions, but I am self taught
>> and run into questions I can't solve thru googling.
>> 
>> I see that G_PI is defined in the header to
>> 3.14159265358979323846
>> 
>> So on my 32 bit Athlon machine, I get limited precision
>> to 15 decimal places, do I need a 64 bit machine for better
>> precision? Or is there a different format to use?
>
>Google?  Did you try Wikipedia?
>
>double is 64 bits everywhere; 52 bits of mantissa gives 15 decimal
>places. (Remember, 1 bit is 0.3 bans).  long double may have the
>precision you're after, again, read Wikipedia.
>
>Ed

Yeah thanks. I finally was pointed to long double, and did a groups.google
search of comp.lang.c for "long double pi" and found alot of discussion
on printing more decimal places of accuracy. It's quite an active question.

I've tried printing G_PI with the %Lf.20 format and I'm still stuck with 
15 decimal places of accuracy.  So I will experiment some with defining
PI by shifting the decimal place by multiplying and see if the %Lf  will do
more digits of precision.

Something for a Saturday afternoon. :-)

zentara

-- 
I'm not really a human, but I play one on earth.
http://zentara.net/japh.html