The back end and libraries are now up for general testing on a variety of boxes and operating systems. The tarball is usually updated as the web page is. To download and install g95 on unix systems, run the following command (originally from Joost Vandevondele):

wget -O - http://ftp.g95.org/g95-x86-
linux.tgz | tar xvfz -

This will create a directory named 'g95-install' in the current directory. Run (or better yet make an appropriate symbolic link to) ./g95-
install/bin/i686-pc-linux-gnu-
g95 in order to run g95.

Cool things you can do with G95

G95 is much more than just a compiler. It is a system for doing computations. There are several very cool things that you can do with g95:


Runtime options

There are many runtime options that can be set by the user. Many of these are left processor-dependent by the standard, but may be set by the end user at runtime. To get a complete list of these options, run any g95-compiled program with --g95. Instead of running your program, you'll get a list of variables and what they are set to.

To modify a setting, set the appropriate environment variable. Under the bash shell this is something like:

export G95_ENDIAN=big  

Corefile Resume

The execution of a G95-compiled programs can be suspended and resumed.

If you interrupt a program by sending it the QUIT signal, which is usually bound to control-backslash the program will write an executable file named 'dump' to the current directory.

Running this file causes the execution of your program to resume from when the dump was written.

andy@fulcrum:~/g95/g95 % cat tst.f90
b = 0.0
do i=1, 10
do j=1, 3000000
call random_number(a)
a = 2.0*a - 1.0
b = b + sin(sin(sin(a)))
enddo
print *, i, b
enddo
end

andy@fulcrum:~/g95/g95 % g95 tst.f90
andy@fulcrum:~/g95/g95 % a.out
1 70.01749
2 830.63153
3 987.717
4 316.48703
5 -426.53815
6 25.407673 (control-\ hit)
Process dumped
7 -694.2718
8 -425.95465
9 -413.81763
10 -882.66223
andy@fulcrum:~/g95/g95 % ./dump
Restarting
............Jumping
7 -694.2718
8 -425.95465
9 -413.81763
10 -882.66223
andy@fulcrum:~/g95/g95 %

Any open files must be present and in the same places as in the original process. If you link against other languages, this may not work.

While the main use is allowing you to preserve the state of a run across a reboot, other possibilities include pushing a long job through a short queue or moving a running process to another machine.

Automatic checkpointing of your program can be done by setting the environment variable G95_CHECKPOINT with the number of seconds to wait between dumps.

New checkpoint files overwrite old checkpoint files.

A program can cause a checkpoint to be written with the following code:

subroutine dump

interface
function getpid() bind(c, name='getpid')
integer :: getpid
end function getpid

subroutine kill(signal, pid) bind(c, name='kill')
integer, value :: signal, pid
end subroutine kill
end interface

call kill(getpid(), 3) ! SIGQUIT = 3

end subroutine dump