Re: printf and long double

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]



 On 4/10/2010 3:03 ÎÎ, Bogdan Cristea wrote:
On Monday 04 October 2010 14:54:46 you wrote:
I wish I could get 24 decimal digits precision with the current long
double (80-bit). I can't get more than 15 digits even in a simple division.
I think that the extended-precision can't give more than 19 decimal
digits of precision (log(10,2^64)=19.2). The quadruple precision can
give at most 34 decimal digits (log(10,2^113)=34).

Please consider the example below:
--------------------------------------------------
long double a = 1.0L/7.0L;
printf("%Lf\n",a);
--------------------------------------------------

Can't get more than 15 digits precision....-:(
Is this a compiler problem or libc's problem? In x86_64 machines the
long double values supposed to give at least 106-bit precision even when
implemented in software. Is gcc compliant with the quadruple notation?
Have you tried to specify manually the number of digits after the decimal
point ?

	long double a = 1.0L/7.0L;
	printf("%'.100Lf\n",a);

On a 64 bits machine the output is:

0.1428571428571428571409210675491330277964152628555893898010253906250000000000000000000000000000000000

regards
Bogdan
Of course I did. But the result you get is the wrong one after the first 20 decimal point digits. The right result is given below with a high precision arithmetic library or with Mathematica or Matlab. And the three results are the same, but not the given one above which is the same for my machine.

0.14285714285714285714285714285714285714285714285714285714285714285714\
28571428571428571428571428571429
--
To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html


[Index of Archives]     [Linux Assembler]     [Git]     [Kernel List]     [Fedora Development]     [Fedora Announce]     [Autoconf]     [Yosemite Campsites]     [Yosemite News]     [GCC Help]
  Powered by Linux