...you mention the possibility it uses 1:st order elements for calculations. If so do you think it's possible in some future to make use of 2:nd order elements?
At the moment it is possible to use 1st or 2nd order triangle and 1st or 2nd order tetrahedron. Script computes centres of gravity and volume of those elements. At the moment these calculations are with certain inaccuracy for 2nd order elements because there are used the same formulas as for 1st order elements.
Is this somehow a limitation of Calculix?
CalxuliX can calculate volumes (may be I will use them), but I didn't found CalculiX to output centres of gravity or, even better, position of integration points. I plan to ask someone about integration over an element shape function which could solve these problems.
Clock cycles: would the calculations run faster if one used a different programming language? Or would it be possible to significantly optimize the code in some way once one get familiar with the code? I'm primarely thinking of code which runs over and over again.
Most of the time CalculiX is running a classical FEM analysis in each iteration. Commercial topology optimizers use slightly different method (SIMP), which pure form is better from the mathematical point of view – there is also an educational code available [1], not such a monster in compare to my trials :-]. I decided for BESO method because I found an explanation which I understood better at that time.
Speed of convergence can be controlled by an input parameter “evolutionary_volume_ratio”, but if you set too big value, you get result of poorer quality. Some potential to get it faster is in the more complex method or their combination, I should read more.
Hexaheral or pentahedral mesh have also theirs potential.
Is it an research project ?
Not officially. Partially I worked on it during some school tasks, but it will not be possible later, not in that way, since I already passed all my courses.
[1]
http://www.topopt.dtu.dk/files/matlab.pdf