Adding configure options when installing a port

[Scott Webster]

On Wed, Jun 16, 2010 at 2:09 PM, Ryan Schmidt <ryandesign at macports.org> wrote:
> So what is OpenMP? It seems it is some kind of multiprocessing library that allows some ImageMagick operations to be faster on multi-processor/multi-core systems. That sounds good, but in #15945 it is implied that no benefit is achieved unless the user sets the OMP_NUM_THREADS environment variable to something useful. Is that still the case or have they now automated that?
>

The number of threads seems to be automated, so disabling openmp would
slow down anyone using imagemagick on a multicore machine.  For
example:

[~@skadi]$ echo $OMP_NUM_THREADS

[~@skadi]$ time convert -size 1920x1080
tile:/opt/local/share/doc/ImageMagick-6.6.2/images/rose.pnm -noise 2
null:

real	0m5.866s
user	0m11.086s
sys	0m0.152s
[~@skadi]$ export OMP_NUM_THREADS=2
[~@skadi]$ time convert -size 1920x1080
tile:/opt/local/share/doc/ImageMagick-6.6.2/images/rose.pnm -noise 2
null:

real	0m5.877s
user	0m11.025s
sys	0m0.156s
[~@skadi]$ export OMP_NUM_THREADS=1
[~@skadi]$ time convert -size 1920x1080
tile:/opt/local/share/doc/ImageMagick-6.6.2/images/rose.pnm -noise 2
null:

real	0m11.106s
user	0m11.005s
sys	0m0.088s