[graph-tool] Open MP installation for mac via macports?

I have installed graph-tool and am doing some tests. One of these was a betweenness calculation, where it appears that only one core was being utilised. I installed via macports whereby the configuration is fully automatic. I’m therefore assuming that macports by default doesn’t enable openmp (—enable-openmp) ? Is there a way to enable this via a macports install, or should I install via home-brew instead? Thanks.