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change proc count to color for MPI_Comm_split

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This commit is contained in:
Steven J. Plimpton
2018-08-02 14:47:20 -06:00
parent b2c75cc0b9
commit b2d1332d46
3 changed files with 32 additions and 34 deletions
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26
src/lammps.cpp
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@ -86,17 +86,17 @@ LAMMPS::LAMMPS(int narg, char **arg, MPI_Comm communicator)
// check if -mpi is first arg
// if so, then 2 apps were launched with one mpirun command
// this means passed communicator (e.g. MPI_COMM_WORLD) is bigger than LAMMPS
// e.g. for client/server coupling with another code
// communicator needs to shrink to be just LAMMPS
// syntax: -mpi P1 means P1 procs for one app, P-P1 procs for second app
// LAMMPS could be either app, based on proc IDs
// e.g. for client/server coupling with another code
// in the future LAMMPS might leverage this in other ways
// universe communicator needs to shrink to be just LAMMPS
// syntax: -mpi color
// color = integer for this app, different than other app(s)
// do the following:
// perform an MPI_Comm_split() to create a new LAMMPS-only subcomm
// NOTE: assuming other app is doing the same thing, else will hang!
// NOTE: this assumes other app(s) does same thing, else will hang!
// re-create universe with subcomm
// store full two-app comm in cscomm
// store full multi-app comm in cscomm
// cscomm is used by CSLIB package to exchange messages w/ other app
// eventually should extend to N > 2 apps launched with one mpirun command
int iarg = 1;
if (narg-iarg >= 2 && (strcmp(arg[iarg],"-mpi") == 0 ||
@ -104,13 +104,9 @@ LAMMPS::LAMMPS(int narg, char **arg, MPI_Comm communicator)
int me,nprocs;
MPI_Comm_rank(communicator,&me);
MPI_Comm_size(communicator,&nprocs);
int p1 = atoi(arg[iarg+1]);
if (p1 <= 0 || p1 >= nprocs)
error->universe_all(FLERR,"Invalid command-line argument");
int which = 0;
if (me >= p1) which = 1;
int color = atoi(arg[iarg+1]);
MPI_Comm subcomm;
MPI_Comm_split(communicator,which,me,&subcomm);
MPI_Comm_split(communicator,color,me,&subcomm);
cscomm = communicator;
communicator = subcomm;
delete universe;
@ -656,8 +652,8 @@ LAMMPS::~LAMMPS()
delete [] suffix;
delete [] suffix2;
// free the MPI comm created by -mpi command-line arg
// it was passed to universe as if origianl universe world
// free the MPI comm created by -mpi command-line arg processed in constructor
// it was passed to universe as if original universe world
// may have been split later by partitions, universe will free the splits
// free a copy of uorig here, so check in universe destructor will still work