@Mac Dude I can run some simple code on threads. I think Isolate is not safe. Thanks for hints. Unfortunentely, nodes have to talk to each other. In particular, there is a combinat:-cartprod() shared between them.

@Markiyan Hirnyk 

Sure, you are right. In my problem each symbol of a system describe some parameter and I wish to decompose my parameter space into open cells. For Groebner methods it seems that it works when I leave indeterminate's list empty and put all symbols into the parameter's list. Well, if I do so for Regular Chains method I got an error that number of variables must be bigger than a number of parameters.

Right now, I am not really sure whether what I've been doing with CellDecomposition is correct or not (analogues command in Mathematica do not distinguish indeterminates and parameters, why this happens in Maple?). Could you give me some hints how I can treat this correctly in CellDecomposition?

Sorry if what I've written here sounds odd.

@Markiyan Hirnyk Consider for example a help page for CylindricalAlgebraicDecompose.