[hackers] Re: x86-64 support

[David Gilbert]

>>>>> "Oliver" == Oliver Fromme <olli at secnetix.de> writes:

Oliver> Narvi <narvi at haldjas.folklore.ee> wrote:
>> On Sat, 26 Apr 2003, M. Warner Losh wrote: > In message:
>> <20030427064014.H40030-100000 at haldjas.folklore.ee> > Narvi
>> <narvi at haldjas.folklore.ee> writes: > : option USE_PI_DIGITS 100
>> >
>> > Only if you could implement it with integer math :-)
>> 
>> where's the problem in that ? most mp libs use integer arithmetic,
>> and x86-64 gives you 64x64->128 bit widening multiplies 8-)

Oliver> You don't need that; the digits of pi can be calculated quite
Oliver> easily with integer math.  This snippet is from my signature
Oliver> collection:

Oliver> int f[9800],b,c=9814,g,i;long
Oliver> a=1e4,d,e,h;main(){for(;b=c,c-=14;i=printf(
Oliver> "%04d",e+d/a),e=d%a)while(g=--b*2)d=h*b+a*(i?f[b]:a/5),h=d/--g,f[b]=d%g;}

With gcc -o pi pi.c, the output is:

[2:19:319]dgilbert at canoe:~/devel> ./pi
187700000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

and so on.  All Zeros.

With gcc -O -o pi pi.c, the output is:

[2:21:321]dgilbert at canoe:~/devel> ./pi
501859265358979323846264338327950288419716939937510582097494459230781640628620899862803482534211706798214808651328230664709384460955058223172535940812848111745028410270193852110555964462294895493038196442881097566593344612847564823378678316

... and so on for many digits.  Neither matches:

echo "scale=200; 4*a(1)" | bc -l
3.141592653589793238462643383279502884197169399375105820974944592307\
81640628620899862803482534211706798214808651328230664709384460955058\
223172535940812848111745028410270193852110555964462294895493038196

Dave.

-- 
============================================================================
|David Gilbert, Velocet Communications.       | Two things can only be     |
|Mail:       dgilbert at velocet.net             |  equal if and only if they |
|http://daveg.ca                              |   are precisely opposite.  |
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