Something strange with g77 ...

From: Arjen Markus (arjen.markus_at_wldelft.nl)
Date: 10/27/03

Date: Mon, 27 Oct 2003 15:51:46 +0100

Hello,

I was trying a few things concerning double and single precision.
Can anyone clarify the result I get with this little program
under Linux using g77:

        implicit none
        real*8 PI, x
        parameter (PI = 3.1415926535897932384)

write(*,*) pi

x = pi
call diff(x)

        write(*,*) x
        stop
        end
        subroutine diff(x)
        real*4 PI4
        parameter (PI4 = 3.1415926535897932384)

real*8 x

        x = x - pi4
        return
        end

When I run this, the answer is (note the last two
digits):

3.14159274
0.

When, instead, I use f77 on a Sun/Solaris machine:

3.1415926535898
0.

Much more as I would expect! (even though the exact
zero still puzzles me).

g77 on that Solaris machine gives the same answer
by the way as g77 on Linux.

Regards,

Arjen

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