20091108

Simple Fortran Cross-Compiler for ARM


Run Fortran code on my handheld ? Are you insane?

That's probably the first thing that comes to your mind after seeing the title of my latest post - but with the power of ARM processors of today, why wouldn't we run Fortran programs on them?

Fortran was (back in the 70's ... and arguably still is) the scientific computing language of choice for many academics and engineers. It became the basis for many of the most advanced matrix-algebra math libraries available to date, including BLAS, LINPACK, and LAPACK, which are used by the most powerful number-crunching machines in the world, not to mention all of the banks and stock-exchanges! What I find more interesting is that the popular math engine known as MATLAB makes heavy use of BLAS and LAPACK, as does a free MATLAB-like environment called Octave.

I should take a step back and say, that the simple cross-compiler I have devised is not in-itself a cross compiler, but a two-step solution using F2C and your friendly-neighborhood cross-GCC ;-) That is, the Fortran code is first translated to C code, and then cross-compiled into machine code. Although many people swear that a well written Fortran code pushed through a good Fortran compiler will always blow away C code (and they probably are right), it's always true that something is better than nothing. The advantage of using F2C is that you don't need to link your programs to libgfortran, and having fewer dependencies is always good in embedded systems.

In any event, F2C (and the resultant libf2c) were authored by several friendly and very smart people who were kind enough to make their software available to the general public on NetLib.Org.

Using a popular perl script called Fort77, and my tiny patch, you should be able to cross-compile Fortran code to object code (.f -> .o) just like you would with C (.c -> .o). You'll need a libf2c.so compiled for ARM as well as f2c.h installed and in your cross-compiler's default search paths. I built the cross-compiled libf2c using an armv5tel-softfloat toolchain using Gentoo's crossdev, and created a small overlay for the package, available here.

I have something special on my evil agenda for this... and will hopefully be announcing something about that within the not-to-distant future!

Lastly ... for all of the gadget-geeks that are reading this... what sort of devices are you hoping to find in your stockings this holiday season? I'm fairly infatuated with the Qualcomm Snapdragon / MSM devices, but the Nokia n900 (with an OMAP chip also looks very tempting).

1 comment:

Christopher Friedt said...

I just thought that I would point out, this project is still happening... and it has something to do with Android :) but that's all I'm saying right now.