Need some help here

[Jerry DeLisle <jvdelisle at verizon dot net>]

I can't get the attached program to work with double precision (kind=8).
If I set working precision to 4 (see attached code) I get the correct
results with gfortran:

 0.1000000       2.991917
  0.2000000       2.967996
  0.3000000       2.929212
  0.4000000       2.877139
  0.5000000       2.813868
  0.6000000       2.741907
  0.7000000       2.664046
  0.8000001       2.583202
  0.9000001       2.502252
   1.000000       2.423863

Intel ifort gives: wrong

 0.1000000       3.115738
  0.2000000       3.216358
  0.3000000       3.299795
  0.4000000       3.364530
  0.5000000       3.409596
  0.6000000       3.434577
  0.7000000       3.439587
  0.8000001       3.425236
  0.9000001       3.392583
   1.000000       3.343084

With wp=8, gfortran and ifort give:

  0.100000000000000      NaN
  0.200000000000000      NaN
  0.300000000000000      NaN
  0.400000000000000      NaN
  0.500000000000000      NaN
  0.600000000000000      NaN
  0.700000000000000      NaN
  0.800000000000000      NaN
  0.900000000000000      NaN
   1.00000000000000      NaN

I am using gfortran:

Reading specs from /home/jerry/usr/lib/gcc/i686-pc-linux-gnu/4.0.0/specs
Configured with: ../gcc/configure --prefix=/home/jerry/usr --enable-
languages=c,f95 : (reconfigured) ../gcc/configure --
prefix=/home/jerry/usr --with-gcc-version-
trigger=/home/jerry/build/gcc/gcc/version.c --enable-languages=c,f95 --
no-create --no-recursion
Thread model: posix
gcc version 4.0.0 20041121 (experimental)

Program attached. Thanks

Jerry

Attachment: rk4.f90
Description: Text document