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Re: [fortran,patch] Patch for PR 14394 - Precision of real type.


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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>  
>



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