BC Note Sent on 9/7/07 to users requesting common set of compilers

The purpose of this note is to keep you informed of the issues and problems we have encountered while working on the pending BC project FY07-03 (Common Set of Open Source Compilers) and also, to seek your input on how we should proceed with the possible implementation of BC project FY07-03.

The GNU compilers under BC team's consideration are:

  • gcc: GNU C compiler
  • g++: GNU C++ compiler
  • g77: GNU Fortran77 compiler
    (operates using the GNU gcc 3.x backend)
  • gfortran: GNU Fortran95 compiler
    (operates using the GNU gcc 4.x backend)
  • g95: Unofficial GNU Fortran95
    (operates using the GNU gcc 4.x backend)

Feedback received from our points of contact can be summarized as follows:

Choice between g95 and gfortran:

  • g95 is more mature than gfortran
  • Codes generated by g95 tend to be much slower than commercial compilers

gcc 3.x and gcc 4.x

  • gcc 3.x and gcc 4.x objects are not compatible
  • Interfacing gcc with MPI on IBM systems gives rise to problems

Based on the above input, the BC team has a number of alternatives. These are:

  • Make the GNU compiler suite available on all systems at the participating sites, but with no MPI support
  • Postpone the release of BC project FY07-03 until incompatibilities between gcc 3.x and gcc 4.x have been satisfactorily resolved.

We would appreciate hearing from you on other alternative recommendations that you may wish to add to the list presented above.

We thank you for your valued input and look forward to your comments.

On Behalf of the BC Team,
BC User Input Coordinator

Feedback Received From one user on 9/11/07

My personal recommendation would be to include gfortran and g95 as standard compilers with g77 (gcc 3.x) available on one platform per site.

gcc 4.x adds many speed and security updates making it a better choice in the long run, but old code may work better with g77.

Commercial compilers should also be available.

MPI support is a requirement - The IBM issue should be fixed before the policy is applied to the IBM machines.

Feedback Received From another user on 9/25/07

I like the above comments and agree with them.