Yay! I've done it: 1160 lines of bash script are now 1215 lines of perl, and:

    'debtree aptitude': 1m2.832s -> 0m0.596s

The new release is available as version 0.9.9 from the debtree web site and has been uploaded for the archive as version 1.0.

This was the starting position, the run time for my complete test set:

    real    22m33.583s
    user    18m29.709s
    sys     4m21.320s

I began with a pure language conversion from bash to perl, i.e. I kept the call-outs to dctrl-tools. This allowed me to easily identify problems in the language conversion by running my test suite, without having to worry that a change might have been caused by getting different data. The language conversion itself was fairly straightforward; most time was spent on finding all the little errors made during the conversion.

This resulted in "only" a 10% speedup:

    real    20m56.368s
    user    18m3.996s
    sys     2m46.986s

So bash itself isn't even horribly slower than perl, even with all the recursion and starting of subshells for calls to grep, sed, etc.

Then I replaced the call-outs to dctrl-tools one by one, adding the dependency on libapt-pkg-perl. And that resulted in the amazing:

    real    0m21.350s
    user    0m19.797s
    sys     0m1.372s

So, from 22 minutes to 21 seconds for 22 graphs, including some pretty complex ones. Not bad.

I had to keep a call-out to dctrl-tools for build dependencies as it turned out libapt-pkg-perl does not expose architecture conditions.

The full conversion process can be seen in the source repository, which was recently moved from my $HOME on alioth to collab-maint.