http://axcas.net is an online computer algebra system I've been working on. I'm working to finish the programming language which is based on C, and I'm adding an ode solver which I plan to use to evaluate special functions.
I release code into the public domain hoping it will be useful. There's some fast code for Groebner basis computations using the F4 algorithm (parallelized - article to follow), and some routines for machine integers e.g. discrete logarithm, factoring, and prime counting.
Build side projects if you have the time. For example, I have a computer algebra system hosted online. Every week I add a couple of algorithms just by working on it when everyone else has gone to bed. Sometimes I get a lot done, sometimes not a lot, it varies. But it has definitely stopped atrophy.
I released some public domain code for computing Groebner bases (F4 and FGLM). I'm hoping these routines will find their way into more systems.
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