Hi Pedro,
Somehow I thought this was a new message, but the date tells me it's from quite some time ago. Replying anyway as it may be interesting to you and all:
On Thu, May 20, 2010 at 4:46 PM, Pedro Lopespedro.lopes@ist.utl.pt wrote something roughly along the lines of:
I was trying to include pragma comments of OpenMp in a PD external, but it does not seem to work for some reason. undefined symbol: GOMP_parallel_start
OpenMP has a run time system that is linked into the executable when you compile with -fopenmp - if you compile a shared object (like a Pd external) with -fopenmp it hopes that the executable that loads it will have the OpenMP run time system inside it. So the fix is simple: just compile Pd itself with -fopenmp, then compile your external with -fopenmp too, and it should Just Work (TM). Attached patch against pd-0.42-5 allowed me to load a slightly modified version of gridflow and see Pd using more than one core:
http://claudiusmaximus.goto10.org/g/tech/pd-gridflow-openmp.png
(After applying the patch, run "autoreconf" to regenerate "./configure")
NB: while it does use more than one core, I just compared with the single core version of gridflow without openmp and it uses only 25% of my cpu (on one core) while the openmp version uses 145% of my cpu (spread over two cores). So, it's no magic bullet...