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Re: [fortran,patch] Patch for PR 14394 - Precision of real type.
- From: Tianjiao Zhang <tjzhang at quantumstates dot com>
- To: Feng Wang <wf_cs at yahoo dot com>
- Cc: fortran <fortran at gcc dot gnu dot org>, stevenb at suse dot de, Paul Brook <paul at codesourcery dot com>
- Date: Wed, 10 Mar 2004 15:30:02 +0800
- Subject: Re: [fortran,patch] Patch for PR 14394 - Precision of real type.
- References: <20040310043448.7688.qmail@web15202.mail.bjs.yahoo.com>
SunOS 5.9 Generic_112233-08 sun4u sparc SUNW,Sun-Fire-880
f77 WorkShop Compilers 4.2
-255.99870413452
On Linux 2.4.18-3smp #1i686 unknown
pgf90 4.0-2
-255.9958332631721
Feng Wang wrote:
>Hi, all
> This patch fix PR 14394. Reported by Bud. Test case:
>cat z.f
> REAL AVS,BVS
> BVS = 1.5747025767
> AVS = TAN(BVS)
> PRINT*,AVS
> END
> There is one problem converting the real type from mpf to gcc tree. With
>-fdump-parse-tree we can see fortran gets the input and parse correctly.
>gfc_conv_mpf_to_tree in trans-const.c use string as the intermediate of the
>conversion. As convert mpf to string, we specify the maximum digits number of
>the real value. In my patch, I loosen the limit.
> I tested real and real*8 type with the patch. The real type got the same
>result with Intel's compiler. But with real*8 type, gfortran gave the result:
>-255.998704134517, compared with Intel's -255.995833263172. The difference of
>them is above 0.002. With calculator I comfirmed the gfortran's result should
>be correct. But can anyone give more comparation with other compilers. What's
>your opinion?
>
>
>Feng Wang
>
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