[Discuss] Test for positive gives wacko results for underflowed values for the gcc compiler suite (including the gcc compiler, and g77 and gfortran compilers)

[pw]

Alan W. Irwin wrote:
> Is this a gcc (and g77 and gfortran) issue?  I would appreciate it if
> somebody would run the above C test codes with different C
> compilers/platforms.
> 
> Alan


I get the same thing.

Intel core duo:

gfortran -v
Using built-in specs.
Target: i386-pc-mingw32
Configured with: ../trunk/configure --prefix=/mingw 
--enable-languages=c,fortran --with-gmp=/home/coudert/local 
--disable-nls --with-ld=/mingw/bin/ld --with-as=/mingw/bin/as 
--disable-werror --enable-bootstrap --enable-threads 
--build=i386-pc-mingw32 --disable-shared --enable-libgomp
Thread model: win32
gcc version 4.3.0 20070522 (experimental)


gfortran test.for -ffixed-line-length-none -pedantic -std=f95 -Wall -o 
test.exe


       DOUBLE PRECISION x, xscale
       x = 1.d-200
       xscale = 1.d+250
       write(*,'(1p3d15.5)') x, xscale, x/xscale
       write(*,*) x/xscale.gt.0.d0
       write(*,*) x/xscale.gt.1.d-305
       write(*,*) log(x/xscale)
       end

test.exe

     1.00000-200    1.00000+250    0.00000D+00
  T
  F
                -Infinity