Define all named MPI constants.

[jeffhammond]

see MPI 4.0 19.1.2

[jeffhammond]

    ! The constants that cannot be used in initialization expressions or assignments in Fortran are as follows:
    ! Buffer address sentinels
    integer :: MPI_BOTTOM          =  0
    integer :: MPI_IN_PLACE        =  1
    integer :: MPI_ARGV_NULL       =  0
    integer :: MPI_ARGVS_NULL      =  0
    integer :: MPI_ERRCODES_IGNORE = -1
    integer :: MPI_UNWEIGHTED      = -1
    integer :: MPI_WEIGHTS_EMPTY   =  0

Only MPI_BOTTOM and MPI_IN_PLACE are handled right now.
Functions that use the others aren't present yet.

[jeffhammond]

    ! thread levels
    integer, parameter :: MPI_THREAD_SINGLE     = 0
    integer, parameter :: MPI_THREAD_FUNNELED   = 1
    integer, parameter :: MPI_THREAD_SERIALIZED = 2
    integer, parameter :: MPI_THREAD_MULTIPLE   = 3

    ! comparisons (communicators and groups)
    integer, parameter :: MPI_IDENT     = 0
    integer, parameter :: MPI_CONGRUENT = 1
    integer, parameter :: MPI_SIMILAR   = 2
    integer, parameter :: MPI_UNEQUAL   = 3

DONE

[jeffhammond]

    ! useful handles
    type(MPI_Comm), parameter     :: MPI_COMM_WORLD    = MPI_Comm(MPI_VAL     = -1000000)
    type(MPI_Comm), parameter     :: MPI_COMM_SELF     = MPI_Comm(MPI_VAL     = -1)

DONE

[jeffhammond]

    ! NULL handles
    type(MPI_Comm), parameter     :: MPI_COMM_NULL     = MPI_Comm(MPI_VAL     = -911)
    type(MPI_Datatype), parameter :: MPI_DATATYPE_NULL = MPI_Datatype(MPI_VAL = -911)
    type(MPI_File), parameter     :: MPI_FILE_NULL     = MPI_File(MPI_VAL     = -911)
    type(MPI_Group), parameter    :: MPI_GROUP_NULL    = MPI_Group(MPI_VAL    = -911)
    type(MPI_Info), parameter     :: MPI_INFO_NULL     = MPI_Info(MPI_VAL     = -911)
    type(MPI_Message), parameter  :: MPI_MESSAGE_NULL  = MPI_Message(MPI_VAL  = -911)
    type(MPI_Op), parameter       :: MPI_OP_NULL       = MPI_Op(MPI_VAL       = -911)
    type(MPI_Request), parameter  :: MPI_REQUEST_NULL  = MPI_Request(MPI_VAL  = -911)
    type(MPI_Win), parameter      :: MPI_WIN_NULL      = MPI_Win(MPI_VAL      = -911)

DONE

[jeffhammond]

    ! IGNORE sentinels
    type(MPI_Status)   :: MPI_STATUS_IGNORE
    type(MPI_Status)   :: MPI_STATUSES_IGNORE

[jeffhammond]

    ! use a ridiculously large value that will always be larger than
    ! what any implementation uses, to avoid having to query the
    ! underlying implementation
    integer, parameter :: MPI_MAX_PROCESSOR_NAME         = (1024*1024)
    integer, parameter :: MPI_MAX_LIBRARY_VERSION_STRING = (1024*1024)
    integer, parameter :: MPI_MAX_ERROR_STRING           = (1024*1024)
    integer, parameter :: MPI_MAX_DATAREP_STRING         = (1024*1024)
    integer, parameter :: MPI_MAX_INFO_KEY               = (1024*1024)
    integer, parameter :: MPI_MAX_INFO_VAL               = (1024*1024)
    integer, parameter :: MPI_MAX_OBJECT_NAME            = (1024*1024)
    integer, parameter :: MPI_MAX_PORT_NAME              = (1024*1024)

[jeffhammond]

    ! built-in ops
    type(MPI_Op), parameter :: MPI_MAX      = MPI_Op(MPI_VAL = -10001)
    type(MPI_Op), parameter :: MPI_MIN      = MPI_Op(MPI_VAL = -10002)
    type(MPI_Op), parameter :: MPI_SUM      = MPI_Op(MPI_VAL = -10003)
    type(MPI_Op), parameter :: MPI_PROD     = MPI_Op(MPI_VAL = -10004)
    type(MPI_Op), parameter :: MPI_MAXLOC   = MPI_Op(MPI_VAL = -10005)
    type(MPI_Op), parameter :: MPI_MINLOC   = MPI_Op(MPI_VAL = -10006)
    type(MPI_Op), parameter :: MPI_BAND     = MPI_Op(MPI_VAL = -10007)
    type(MPI_Op), parameter :: MPI_BOR      = MPI_Op(MPI_VAL = -10008)
    type(MPI_Op), parameter :: MPI_BXOR     = MPI_Op(MPI_VAL = -10009)
    type(MPI_Op), parameter :: MPI_LAND     = MPI_Op(MPI_VAL = -10010)
    type(MPI_Op), parameter :: MPI_LOR      = MPI_Op(MPI_VAL = -10011)
    type(MPI_Op), parameter :: MPI_LXOR     = MPI_Op(MPI_VAL = -10012)
    type(MPI_Op), parameter :: MPI_REPLACE  = MPI_Op(MPI_VAL = -10013)
    type(MPI_Op), parameter :: MPI_NO_OP    = MPI_Op(MPI_VAL = -10014)

[jeffhammond]

Currently, only these are missing:

MPI_BSEND_OVERHEAD is missing
MPI_KEYVAL_INVALID is missing
MPI_ROOT is missing
MPI_MAX_STRINGTAG_LEN is missing
MPI_MAX_PSET_NAME_LEN is missing
MPI_PACKED is missing

Some constants may be present but not yet supported in convert_constants.h...