Feat: Implement Wrappers of MPI_COMM_CREATE and MPI_GROUP_RANGE_INCL (#132)

* Feat: Implement Wrappers of MPI_COMM_CREATE and MPI_GROUP_RANGE_INCL

* Update test

* Fix: Support 2D ranges array

* Apply code review

Author: adit4443ya

src/mpi.f90

@@ -17,6 +17,7 @@ module mpi
     integer, parameter :: MPI_SUCCESS = 0
 
     integer, parameter :: MPI_COMM_WORLD = -1000
+    integer, parameter :: MPI_COMM_NULL = -1001
     real(8), parameter :: MPI_IN_PLACE = -1002
     integer, parameter :: MPI_SUM = -2300
     integer, parameter :: MPI_MAX = -2301
@@ -49,6 +50,10 @@ module mpi
         module procedure MPI_Comm_Group_proc
     end interface MPI_Comm_Group
 
+    interface MPI_Comm_create
+        module procedure MPI_Comm_create_proc
+    end interface MPI_Comm_create
+
     interface MPI_Group_free
         module procedure MPI_Group_free_proc
     end interface MPI_Group_free
@@ -57,6 +62,11 @@ module mpi
         module procedure MPI_Group_size_proc
     end interface MPI_Group_size
 
+    interface MPI_Group_range_incl
+        module procedure MPI_Group_range_incl_proc
+    end interface MPI_Group_range_incl
+
+
     interface MPI_Comm_dup
         module procedure MPI_Comm_dup_proc
     end interface MPI_Comm_dup
@@ -175,6 +185,16 @@ integer(kind=MPI_HANDLE_KIND) function handle_mpi_comm_f2c(comm_f) result(c_comm
         end if
     end function handle_mpi_comm_f2c
 
+    integer(kind=MPI_HANDLE_KIND) function handle_mpi_comm_c2f(comm_c) result(f_comm)
+        use mpi_c_bindings, only: c_mpi_comm_c2f, c_mpi_comm_null
+        integer(kind=mpi_handle_kind), intent(in) :: comm_c
+        if (comm_c == c_mpi_comm_null) then
+            f_comm = MPI_COMM_NULL
+        else
+            f_comm = c_mpi_comm_c2f(comm_c)
+        end if
+    end function handle_mpi_comm_c2f
+
     integer(kind=MPI_HANDLE_KIND) function handle_mpi_info_f2c(info_f) result(c_info)
         use mpi_c_bindings, only: c_mpi_info_f2c, c_mpi_info_null
         integer, intent(in) :: info_f
@@ -350,6 +370,51 @@ subroutine MPI_Group_free_proc(group, ierror)
         end if
     end subroutine MPI_Group_free_proc
 
+    subroutine MPI_Group_range_incl_proc(group, n, ranks, newgroup, ierror)
+        use mpi_c_bindings, only: c_mpi_group_range_incl, c_mpi_group_f2c, c_mpi_comm_c2f, c_mpi_group_c2f
+        use iso_c_binding, only: c_int, c_ptr
+        integer, intent(in) :: group
+        integer, intent(in) :: n
+        integer, dimension(:,:), intent(in) :: ranks
+        integer, intent(out) :: newgroup
+        integer, optional, intent(out) :: ierror
+        integer(kind=MPI_HANDLE_KIND) :: c_group, c_newgroup
+        integer(c_int) :: local_ierr
+
+        c_group = c_mpi_group_f2c(group)
+        local_ierr = c_mpi_group_range_incl(c_group, n, ranks, c_newgroup)
+        newgroup = c_mpi_group_c2f(c_newgroup)
+
+        if (present(ierror)) then
+            ierror = local_ierr
+        else if (local_ierr /= MPI_SUCCESS) then
+            print *, "MPI_Group_incl failed with error code: ", local_ierr
+        end if
+    end subroutine MPI_Group_range_incl_proc
+
+    subroutine MPI_Comm_create_proc(comm, group, newcomm, ierror)
+        use mpi_c_bindings, only: c_mpi_comm_create, c_mpi_comm_f2c, c_mpi_comm_c2f, c_mpi_group_f2c, c_mpi_comm_null
+        use iso_c_binding, only: c_int, c_ptr
+        integer, intent(in) :: comm
+        integer, intent(in) :: group
+        integer, intent(out) :: newcomm
+        integer, optional, intent(out) :: ierror
+        integer(kind=MPI_HANDLE_KIND) :: c_comm, c_group, c_newcomm
+        integer(c_int) :: local_ierr
+
+        c_comm = handle_mpi_comm_f2c(comm)
+        c_group = c_mpi_group_f2c(group)
+        local_ierr = c_mpi_comm_create(c_comm, c_group, c_newcomm)
+
+        newcomm = handle_mpi_comm_c2f(c_newcomm)
+
+        if (present(ierror)) then
+            ierror = local_ierr
+        else if (local_ierr /= MPI_SUCCESS) then
+            print *, "MPI_Comm_create failed with error code: ", local_ierr
+        end if
+    end subroutine MPI_Comm_create_proc
+
     subroutine MPI_Comm_dup_proc(comm, newcomm, ierror)
         use mpi_c_bindings, only: c_mpi_comm_dup, c_mpi_comm_c2f
         integer, intent(in) :: comm

src/mpi_c_bindings.f90

@@ -17,6 +17,7 @@ module mpi_c_bindings
     integer(kind=MPI_HANDLE_KIND), bind(C, name="c_MPI_REAL") :: c_mpi_real
     integer(kind=MPI_HANDLE_KIND), bind(C, name="c_MPI_INT") :: c_mpi_int
     integer(kind=MPI_HANDLE_KIND), bind(C, name="c_MPI_COMM_WORLD") :: c_mpi_comm_world
+    integer(kind=MPI_HANDLE_KIND), bind(C, name="c_MPI_COMM_NULL") :: c_mpi_comm_null
     integer(kind=MPI_HANDLE_KIND), bind(C, name="c_MPI_SUM") :: c_mpi_sum
     integer(kind=MPI_HANDLE_KIND), bind(C, name="c_MPI_MAX") :: c_mpi_max
     integer(kind=MPI_HANDLE_KIND), bind(C, name="c_MPI_LOGICAL") :: c_mpi_logical
@@ -338,5 +339,22 @@ function c_mpi_group_free(group) bind(C, name="MPI_Group_free")
             integer(c_int) :: c_mpi_group_free
         end function c_mpi_group_free
 
+        function c_mpi_group_range_incl(group, n, ranges, c_newgroup) bind(C, name="MPI_Group_range_incl")
+            use iso_c_binding, only: c_ptr, c_int
+            integer(kind=MPI_HANDLE_KIND), value :: group
+            integer(c_int), value :: n
+            integer(c_int), dimension(*)  :: ranges
+            integer(kind=MPI_HANDLE_KIND) :: c_newgroup
+            integer(c_int) :: c_mpi_group_range_incl
+        end function c_mpi_group_range_incl
+
+        function c_mpi_comm_create(comm, group, newcomm) bind(C, name="MPI_Comm_create")
+            use iso_c_binding, only: c_ptr, c_int
+            integer(kind=MPI_HANDLE_KIND), value :: comm
+            integer(kind=MPI_HANDLE_KIND), value :: group
+            integer(kind=MPI_HANDLE_KIND), intent(out) :: newcomm
+            integer(c_int) :: c_mpi_comm_create
+        end function c_mpi_comm_create
+
     end interface
 end module mpi_c_bindings

src/mpi_constants.c

@@ -4,22 +4,30 @@ MPI_Status* c_MPI_STATUSES_IGNORE = MPI_STATUSES_IGNORE;
 
 MPI_Info c_MPI_INFO_NULL = MPI_INFO_NULL;
 
-MPI_Comm c_MPI_COMM_WORLD = MPI_COMM_WORLD;
+void* c_MPI_IN_PLACE = MPI_IN_PLACE;
+
+// DataType Declarations
 
 MPI_Datatype c_MPI_DOUBLE = MPI_DOUBLE;
 
 MPI_Datatype c_MPI_FLOAT = MPI_FLOAT;
 
 MPI_Datatype c_MPI_INT = MPI_INT;
 
-void* c_MPI_IN_PLACE = MPI_IN_PLACE;
+MPI_Datatype c_MPI_LOGICAL = MPI_LOGICAL;
+
+MPI_Datatype c_MPI_CHARACTER = MPI_CHARACTER;
+
+MPI_Datatype c_MPI_REAL = MPI_REAL;
+
+// Operation Declarations
 
 MPI_Op c_MPI_SUM = MPI_SUM;
 
 MPI_Op c_MPI_MAX = MPI_MAX;
 
-MPI_Datatype c_MPI_LOGICAL = MPI_LOGICAL;
+// Communicators Declarations
 
-MPI_Datatype c_MPI_CHARACTER = MPI_CHARACTER;
+MPI_Comm c_MPI_COMM_NULL = MPI_COMM_NULL;
 
-MPI_Datatype c_MPI_REAL = MPI_REAL;
+MPI_Comm c_MPI_COMM_WORLD = MPI_COMM_WORLD;

tests/comm_create_1.f90

@@ -0,0 +1,43 @@
+program minimal_mre_range
+  use mpi
+  implicit none
+
+  integer :: ierr, rank, new_rank, size
+  integer :: group_world, group_range, new_comm
+  integer, dimension(1,3) :: range   ! 1D array to define a single range
+  integer :: i
+
+  call MPI_INIT(ierr)
+  call MPI_COMM_RANK(MPI_COMM_WORLD, rank, ierr)
+  call MPI_COMM_SIZE(MPI_COMM_WORLD, size, ierr)
+
+  ! Get the group of MPI_COMM_WORLD
+  call MPI_COMM_GROUP(MPI_COMM_WORLD, group_world, ierr)
+
+  ! Define 1D range: start, end, stride
+  range(1,1) = 0         ! start
+  range(1,2) = size - 1  ! end
+  range(1,3) = 1         ! stride
+
+
+  ! Create a new group that includes all ranks
+  call MPI_GROUP_RANGE_INCL(group_world, 1, range, group_range, ierr)
+
+  ! Create new communicator
+  call MPI_COMM_CREATE(MPI_COMM_WORLD, group_range, new_comm, ierr)
+
+  ! Print participation
+  if (new_comm /= MPI_COMM_NULL) then
+    call MPI_COMM_RANK(new_comm, new_rank, ierr)
+    if (ierr /= MPI_SUCCESS) error stop "MPI_COMM_RANK on new_comm failed"
+    print *, 'Global rank', rank, 'is in new_comm with local rank', new_rank
+  else
+    print *, 'Rank', rank, 'is NOT in the new communicator.'
+  end if
+
+  ! Free groups (no comm_free)
+  call MPI_GROUP_FREE(group_range, ierr)
+  call MPI_GROUP_FREE(group_world, ierr)
+
+  call MPI_FINALIZE(ierr)
+end program minimal_mre_range