How to define a bool in the rolling model header?

Hi Joshua!

It is more or less correct as you did it.
Just one remark:

• Set default values / initialize variables always in the constructor or (better) just before in the initializer list, like coeffRollFrict in rolling_model_epsd2.h#L70
  In your case this would be
  RollingModel(class LAMMPS * lmp, IContactHistorySetup * hsetup) : Pointers(lmp), coeffRollFrict(NULL), tipreach_flag(false)
{ ...

If you want to store the value by PARTICLE I would use the great fix property/atom, because it implements all the MPI stuff to communicate the value to ghost particles when leaving a subdomain
On Scriptlevel
fix fppacc all property/atom fppacc scalar yes yes yes 0
run 0

In your C++-code you can now access this fix by:

updFix = NULL;
for (int ifix = 0; ifix < (lmp->modify->nfix); ifix++){
updFix = static_cast(modify->find_fix_id("fppacc"));
}

and use it later like this:

if (updFix->vector_atom[i]>=something)
do_anything()

Of course you can create the fix on C++ level, see FixCfdCouplingForce::post_create() for an example.

When you need the flag for every PAIR and don't need it after the contact has been lost just add a new history value like the rolling_model_epsd do.

Best,
Christian

I think you mixed up pointers and values of variables.
in contact interface bool tipreach is a place in the memory (oposite to * contact_history which only holds a pointer to the memory where contact_history is stored)
so when accessing the VALUE of tipreach you should only need cdata.tipreach_flag=true; to set the value.
with *treach_flag=true you try to set the pointer to true which is not valid and I think you don't need a pointer to cdata.tipreach_flag (I think you has been inspired by contact_history, but c_h is a vector of type double and not a single value ..).

I think cdata is only a single struct which is used as input/output parameter in the function which handles contacts (pair gran und wall gran for example). It is filled for every contact detected in pair algorithmus and sent to the normal- und rolling models.
What you need is a history storage place for your flag, as I said you should use the existing contact_history.
something like this might work:

history_offset = hsetup->add_history_value("r_torquex_old", "1");
hsetup->add_history_value("r_torquey_old", "1");
hsetup->add_history_value("the_flag", "1"); //add a 4th contcact-history value

in collision

double * const c_history = &cdata.contact_history[history_offset];
if (c_history[3])
//when condition has been true in LAST contact loop do something interesting
c_history[3]=condition?1:0; //4th value of contact_history is storage for flag

I'm aware that one should not store a bool in a double, but this makes live easier than implementing a boolean contact history storage