ÔÚ 2002-02-19 11:46:00 you wrote£º
>....
>> It is weird enough for me that u doesn't equal to tmp2,that is where x86 and mips differ.
>>
>> the output from my P4:
>> rounding is TONEAREST
>> x=(7fefffff,ffffffff),y=(00000000,00000001)
>> x=(7fefffff,ffffffff),y=(04d00000,00000000)
>> 1/y=7b100000,00000000
>> n=04d00000,nn=06100000,ww=(00000000,00000000),w=(04d00000,00000000),l=79d00000
>> u=(7fefffff,ffffffff),d=(41400000,00000000),w=(7ea00000,00000000)
>> d*w=(7ff00000,00000000),u.x-d*w=(fff00000,00000000),u=(fca00000,00000000) <--notice this
>> u=(fca00000,00000000),d=(c1300000,00000000),w=(7b600000,00000000)
>> d*w=(fca00000,00000000),u.x-d*w=(00000000,00000000),u=(00000000,00000000)
>> x=(00000000,00000000),y=(04d00000,00000000)
>>
>> output from mipsel:
>> rounding is TONEAREST
>> x=(7fefffff,ffffffff),y=(00000000,00000001)
>> x=(7fefffff,ffffffff),y=(04d00000,00000000)
>> 1/y=7b100000,00000000
>> n=04d00000,nn=06100000,ww=(00000000,00000000),w=(04d00000,00000000),l=79d00000
>> u=(7fefffff,ffffffff),d=(41400000,00000000),w=(7ea00000,00000000)
>> d*w=(7ff00000,00000000),u.x-d*w=(fff00000,00000000),u=(fff00000,00000000) <--notice this
>> u=(fff00000,00000000),d=(fff00000,00000000),w=(7eb00000,00000000)
>> d*w=(fff00000,00000000),u.x-d*w=(7ff7ffff,ffffffff),u=(7ff7ffff,ffffffff)
>> u=(7ff7ffff,ffffffff),d=(7ff7ffff,ffffffff),w=(7eb00000,00000000)
>> d*w=(7ff7ffff,ffffffff),u.x-d*w=(7ff7ffff,ffffffff),u=(7ff7ffff,ffffffff)
>> u=(7ff7ffff,ffffffff),d=(7ff7ffff,ffffffff),w=(7eb00000,00000000)
>> d*w=(7ff7ffff,ffffffff),u.x-d*w=(7ff7ffff,ffffffff),u=(7ff7ffff,ffffffff)
>> u=(7ff7ffff,ffffffff),d=(7ff7ffff,ffffffff),w=(7eb00000,00000000)
>> d*w=(7ff7ffff,ffffffff),u.x-d*w=(7ff7ffff,ffffffff),u=(7ff7ffff,ffffffff)
>
>You're right. Not a bug. Internally your P4 uses more than 64 bits in its
Then libm needs a fix. I see,Thank you.
>calculations. Here's my test and output from my AMD, Sun and MIPS:
>
>typedef union number_s {
> long long ll;
> double d;
>} t_number;
>
>#define P(x) printf(#x "=%e %016llx\n", x.d, x.ll)
>
>int main()
>{
> t_number u, d, w, t, r;
>
> u.ll = 0x7fefffffffffffff;
> d.ll = 0x4140000000000000;
> w.ll = 0x7ea0000000000000;
> t.d = d.d * w.d;
> t.d = u.d - t.d;
> r.d = (u.d - d.d * w.d);
> P(u);
> P(d);
> P(w);
> P(r);
> P(t);
>}
>
>AMD:
>u=1.797693e+308 7fefffffffffffff
>d=2.097152e+06 4140000000000000
>w=8.572069e+301 7ea0000000000000
>r=-1.995840e+292 fca0000000000000
>t=-inf fff0000000000000
>
>Sun:
>u=1.797693e+308 7fefffffffffffff
>d=2.097152e+06 4140000000000000
>w=8.572069e+301 7ea0000000000000
>r=-Inf fff0000000000000
>t=-Inf fff0000000000000
>
>MIPS:
>u=1.797693e+308 7fefffffffffffff
>d=2.097152e+06 4140000000000000
>w=8.572069e+301 7ea0000000000000
>r=-inf fff0000000000000
>t=-inf fff0000000000000
>
>
>/Kjeld
>
>--
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Regards
Zhang Fuxin
fxzhang@ict.ac.cn
