CVODE constraints and max_noinlinear_iterations options #2303
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Uses CVodeSetConstraints function to allow constraints to be applied to variables to be: none (default, no constraint), positive, non_negative, negative, or non_positive.
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| // Loop over 2D variables | ||
| for (std::vector<BoutReal>::size_type i = 0; i < f2dtols.size(); i++) { | ||
| if (bndry && !f2d[i].evolve_bndry) { | ||
| continue; | ||
| } | ||
| abstolvec_data[p] = f2dtols[i]; | ||
| option_data[p] = f2dtols[i]; |
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warning: do not use pointer arithmetic [cppcoreguidelines-pro-bounds-pointer-arithmetic]
option_data[p] = f2dtols[i];
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Don't understand this error - I don't think there's any pointer arithmetic here, just accessing a C-array with an int index...
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The C-array indexing is basically sugar for pointer arithmetic: the compiler turns it into *(option_data + p) = f2dtols[i] (and this is why array[0] == 0[array] works even though it looks like bad magic). This is a bit more obvious looking at the function signature, which takes a BoutReal* rather than an array type.
There isn't a great deal we can do to do this properly, given that we don't own N_Vector (and also that it's pretty much an opaque pointer). In C++20, we could take a std::span here instead of BoutReal*.
I think we could use N_VMake_Parallel to create abstolvec with our own data (e.g. Array), and then pass that directly to set_abstol_values.
(Incidentally, I'm pretty sure we could do something like that to avoid copying the derivatives in and out of the solver's data structures if we could somehow allocate a big block of consecutive memory for the derivatives in the first place)
| @@ -686,7 +776,7 @@ void CvodeSolver::loop_abstol_values_op(Ind2D UNUSED(i2d), BoutReal* abstolvec_d | |||
| if (bndry && !f3d[i].evolve_bndry) { | |||
| continue; | |||
| } | |||
| abstolvec_data[p] = f3dtols[i]; | |||
| option_data[p] = f3dtols[i]; | |||
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warning: do not use pointer arithmetic [cppcoreguidelines-pro-bounds-pointer-arithmetic]
option_data[p] = f3dtols[i];
^
Reduces code duplication.
Interface to two more options provided by CVODE solver:
solver:apply_positivity_constraints- if set to true, read an optionpositivity_constraintin each variable subsection, which can be set tonone(the default),positive,non_negative,negative, ornon_positive. If any of these constraints is violated at the end of an internal timestep, CVODE will go back to the previous step and continue with a shorter timestep.solver:max_nonlinear_iterations- allow changing the maximum number of nonlinear iterations allowed for each timestep. CVODE default is 3. Might be useful to increase if the number of linear iterations per Newton iteration is small, but a very brief test did not observe any benefit.