floating point precision problem

[syntax]

hi,
i need to get high presion float numbers.

say, i need pi = 22/7.0 = 3.142857....(up to 80 digits)

is it possible ?

does gcc/g++ compiler can give such type of high precision??

plz GIVE A SMALL CODE HOW CAN I ACHIEVE THAT ? which way, i have to
write the code??
Question2: AT most how much precision can gcc/g++ AND VC++ Give?

can i write

double double double double x = 22/7.0 ? ... so that it could hold
highly precise result.

[jacob navia]

"syntax" <sa*****@yahoo. com.hk> wrote in message
news:5c******** *************** ***@posting.goo gle.com...

hi,
i need to get high presion float numbers.

say, i need pi = 22/7.0 = 3.142857....(up to 80 digits)

is it possible ?

does gcc/g++ compiler can give such type of high precision??

plz GIVE A SMALL CODE HOW CAN I ACHIEVE THAT ? which way, i have to
write the code??
Question2: AT most how much precision can gcc/g++ AND VC++ Give?

can i write

double double double double x = 22/7.0 ? ... so that it could hold
highly precise result.

Use lcc-win32.
For instance:
#include <qfloat.h>
int main(void)
{
qfloat p = 2;
printf("%1.80qf \n",sqrt(p));
return 0;
}
will produce:
1.4142135623730 950488016887242 096980785696718 753769480731766 7973799073
247846210704
Qfloats have a precision of 350 bits, approx 100 digits.

http://www.cs.virginia.edu/~lcc-win32

[Julian V. Noble]

syntax wrote:

hi,
i need to get high presion float numbers.

say, i need pi = 22/7.0 = 3.142857....(up to 80 digits)

is it possible ?

does gcc/g++ compiler can give such type of high precision??

plz GIVE A SMALL CODE HOW CAN I ACHIEVE THAT ? which way, i have to
write the code??

Question2: AT most how much precision can gcc/g++ AND VC++ Give?

can i write

double double double double x = 22/7.0 ? ... so that it could hold
highly precise result.

As noted previously in this group, several high-precision libraries in
standard C have been written and are available for download.

A Google search of "high precision arithmetic in C" yields

http://crd.lbl.gov/~dhbailey/mpdist/mpdist.html

among about 126,000 hits.

--
Julian V. Noble
Professor Emeritus of Physics
jv*@lessspamfor mother.virginia .edu
^^^^^^^^^^^^^^^ ^^^
http://galileo.phys.virginia.edu/~jvn/

"God is not willing to do everything, and thereby take away our free wiil
and that share of glory that rightfully belongs to ourselves."
-- N. Machiavelli, "The Prince".

[Malcolm]

"syntax" <sa*****@yahoo. com.hk> wrote in message

i need to get high presion float numbers.

Generally C compilers will restrict themselves to types supported in
hardware, which are usually 32, 64 and sometimes 80 bits.
If the hardware has high-precison doubles, such as 128 bits, the compiler is
likely to provide an extension such as long long double. However such
hardware is not in common use.

A double is enough precision for almost all uses. If you need more precision
you need to emulate floating point in software (libraries are available to
do just that).
If you want to calculate PI to great precison, there are better algorithms
available that don't rely on arbitrary-precison floating point arithmetic.

[P.J. Plauger]

"Malcolm" <ma*****@55bank .freeserve.co.u k> wrote in message
news:bv******** **@newsg1.svr.p ol.co.uk...

"syntax" <sa*****@yahoo. com.hk> wrote in message

i need to get high presion float numbers.
Generally C compilers will restrict themselves to types supported in
hardware, which are usually 32, 64 and sometimes 80 bits.
If the hardware has high-precison doubles, such as 128 bits, the compiler

is likely to provide an extension such as long long double. However such
hardware is not in common use.

Sun Sparcs are in pretty common use. They have 128-bit floating-point
format. And every compiler I know calls it long double.

P.J. Plauger
Dinkumware, Ltd.
http://www.dinkumware.com

[Sidney Cadot]

syntax wrote:

hi,
i need to get high presion float numbers.
Could you give some background about what you need these for? Chances
are, your reasons for wanting this are not sound.
say, i need pi = 22/7.0 = 3.142857....(up to 80 digits)

is it possible ?
Yes, but not in standard C using any compiler I am aware of.
does gcc/g++ compiler can give such type of high precision??
C (and C++) compilers provide floating-point types that generally map
onto types supported by the hardware, so you should not be asking about
a particular compiler, but about a particular hardware platform.

I do not know any hardware platform that supports over 128 bits of
precision for floating point values.
plz GIVE A SMALL CODE HOW CAN I ACHIEVE THAT ? which way, i have to
write the code??
PLEASE DON'T SHOUT. Thank you.

In standard C, you can't. You might want to look at add-on libraries
(e.g., GMP, the GNU Multi-Precision Library). Or perhaps you don't even
want C ("bc" is nice for small high-precision numerical algorithms).
Question2: AT most how much precision can gcc/g++ AND VC++ Give?
Depends on the hardware. Usual sizes for floating point types are 32,
64, 80, and 128 bits. This is a long way short of the 80 digits you
claim you need.
can i write

double double double double x = 22/7.0 ? ... so that it could hold
highly precise result.

No.

Best regards,

Sidney

[Keith Thompson]

sa*****@yahoo.c om.hk (syntax) writes:

hi,
i need to get high presion float numbers.

say, i need pi = 22/7.0 = 3.142857....(up to 80 digits)

is it possible ?
<OT>
I hope you're aware that 22/7.0, however precisely you compute it, is
not a very accurate representation of the mathematical constant pi.
22/7.0 is 3.(142857)* (that's a repeating decimal, 3.142857142857. ..);
pi is 3.1415926535... . (The notation for a repeating decimal is
something I just made up.)
</OT>
Question2: AT most how much precision can gcc/g++ AND VC++ Give?

can i write

double double double double x = 22/7.0 ? ... so that it could hold
highly precise result.

There are only three predefined floating-point types in standard C:
float, double, and long double. A compiler could provide, say,
"long long double" as an extension, but I don't know of any system
with direct hardware support for more than three sizes. Another
poster mentioned a "qfloat" type provided by one particular compiler,
but of course that's non-portable (which isn't necessarily a reason
not to use it).

If you want a more portable solution, there are a number of
extended-precision numeric libraries floating (sic) around. Probably
the best known is gmp, the GNU MP library, available from gnu.org.

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://www.sdsc.edu/~kst>
Schroedinger does Shakespeare: "To be *and* not to be"

[Mark McIntyre]

On Fri, 30 Jan 2004 20:32:00 GMT, in comp.lang.c , "P.J. Plauger"
<pj*@dinkumware .com> wrote:

"Malcolm" <ma*****@55bank .freeserve.co.u k> wrote in message
news:bv******* ***@newsg1.svr. pol.co.uk...

If the hardware has high-precison doubles, such as 128 bits, the compiler is
likely to provide an extension such as long long double. However such
hardware is not in common use.
Sun Sparcs are in pretty common use.

for some definitions of common !
I've not seen too many of them in kids bedrooms, internet cafes, etc.
They have 128-bit floating-point
format. And every compiler I know calls it long double.

Doesn't intel have a similar longish double? Hardware specific
question of course, offtopic here.
--
Mark McIntyre
CLC FAQ <http://www.eskimo.com/~scs/C-faq/top.html>
CLC readme: <http://www.angelfire.c om/ms3/bchambless0/welcome_to_clc. html>
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[CBFalconer]

Keith Thompson wrote:

sa*****@yahoo.c om.hk (syntax) writes:

i need to get high presion float numbers.
say, i need pi = 22/7.0 = 3.142857....(up to 80 digits)
is it possible ?

<OT>
I hope you're aware that 22/7.0, however precisely you compute it, is
not a very accurate representation of the mathematical constant pi.
22/7.0 is 3.(142857)* (that's a repeating decimal, 3.142857142857. ..);
pi is 3.1415926535... . (The notation for a repeating decimal is
something I just made up.)
</OT>

No it isn't (just made up). AGMTA. However pi is not a repeating
decimal :-) Some of the best rational approximations I know for
pi are:

22 / 7
355 / 113
833719 / 265381
1146408 / 364913
4272943 / 1360120
5419351 / 1725033
63885804 / 20335483
74724506 / 23785549
80132847 / 25510582

with the error decreasing by about a factor of 4 or more for
those. They assume a correct value is 3.1414926535897 93.

--
Chuck F (cb********@yah oo.com) (cb********@wor ldnet.att.net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home .att.net> USE worldnet address!

[syntax]

thanks jacob navia

win lcc-win32 is working....

some of you are suggesting to use GMP library. i dont know even
whetehr my compiler has that library..my compiler is gcc/g++ 2.98
version.

in order to see whether GMP is there
i simply wrote $ ls /usr/lib/
and i found something like this (along with other libraries)

libgmp.a libgmp.so
libgmp.so.3
libgmp.so.3.1.1

do you think my compiler has GMP support?

if so can you plz give me code to calculate sqrt(2) upto 80
digits??.. so that i am be convinced that my GMP library works well.

i am working through telnet..Red Hat linux.7.0.1
does Higher version of linux( Red hat linux 9 ) supports GMP library
in-built??


Keith Thompson <ks***@mib.or g> wrote in message news:<ln******* *****@nuthaus.m ib.org>...

sa*****@yahoo.c om.hk (syntax) writes:

hi,
i need to get high presion float numbers.

say, i need pi = 22/7.0 = 3.142857....(up to 80 digits)

is it possible ?

<OT>
I hope you're aware that 22/7.0, however precisely you compute it, is
not a very accurate representation of the mathematical constant pi.
22/7.0 is 3.(142857)* (that's a repeating decimal, 3.142857142857. ..);
pi is 3.1415926535... . (The notation for a repeating decimal is
something I just made up.)
</OT>

Question2: AT most how much precision can gcc/g++ AND VC++ Give?

can i write

double double double double x = 22/7.0 ? ... so that it could hold
highly precise result.

There are only three predefined floating-point types in standard C:
float, double, and long double. A compiler could provide, say,
"long long double" as an extension, but I don't know of any system
with direct hardware support for more than three sizes. Another
poster mentioned a "qfloat" type provided by one particular compiler,
but of course that's non-portable (which isn't necessarily a reason
not to use it).

If you want a more portable solution, there are a number of
extended-precision numeric libraries floating (sic) around. Probably
the best known is gmp, the GNU MP library, available from gnu.org.