NAME

       MPI_Type_struct -  Creates a struct datatype

SYNOPSIS

       int MPI_Type_struct(int count, int array_of_blocklengths[], MPI_Aint array_of_displacements[],
       MPI_Datatype array_of_types[], MPI_Datatype *newtype)

INPUT PARAMETERS

       count  -   number   of   blocks   also   number   of  entries  in  arrays  array_of_types,
              array_of_displacements, and array_of_blocklengths (non-negative integer)
       array_of_blocklengths
              - number of elements in each block (non-negative integer)
       array_of_displacements
              - byte displacement of each block (integer)
       array_of_types
              - types of elements in each block (handle)

OUTPUT PARAMETERS

       newtype
              - new datatype (handle)

NOTES

       If an upperbound is set explicitly by using the MPI datatype MPI_UB  ,  the  corresponding
       index must be positive.

       The  MPI  standard  originally made vague statements about padding and alignment; this was
       intended to allow the simple definition of structures that could  be  sent  with  a  count
       greater than one.  For example,
       struct { int a; char b; } foo;

       may  have  sizeof(foo)  >  sizeof(int)  +  sizeof(char)  ;  for  example,  sizeof(foo)  ==
       2*sizeof(int) .  The initial version of the MPI standard defined the extent of a  datatype
       as  including  an  epsilon that would have allowed an implementation to make the extent an
       MPI datatype for this structure equal to 2*sizeof(int) .

       However,  since  different  systems  might  define  different  paddings,  there  was  much
       discussion  by  the  MPI  Forum  about  what  was  the  correct  value of epsilon, and one
       suggestion was to define epsilon as zero.  This would have been the best thing  to  do  in
       MPI  1.0,  particularly since the MPI_UB type allows the user to easily set the end of the
       structure.   Unfortunately,  this  change  did  not  make  it  into  the  final  document.
       Currently,  this  routine  does not add any padding, since the amount of padding needed is
       determined by the compiler that the user is using to build their code,  not  the  compiler
       used  to construct the MPI library.  A later version of MPICH may provide for some natural
       choices of padding (e.g., multiple of the size of the largest basic member), but users are
       advised  to  never  depend on this, even with vendor MPI implementations.  Instead, if you
       define a structure datatype and wish  to  send  or  receive  multiple  items,  you  should
       explicitly  include an MPI_UB entry as the last member of the structure.  For example, the
       following code can be used for the structure foo
       blen[0] = 1; array_of_displacements[0] = 0; oldtypes[0] = MPI_INT;
       blen[1] = 1; array_of_displacements[1] = &foo.b - &foo; oldtypes[1] = MPI_CHAR;
       blen[2] = 1; array_of_displacements[2] = sizeof(foo); oldtypes[2] = MPI_UB;
       MPI_Type_struct(3, blen, array_of_displacements, oldtypes, &newtype);

REMOVED FUNCTION

       The current MPI standard defines  this  routine  as  removed.  The  user  should  use  the
       replacement routine.  The replacement for this routine is MPI_Type_create_struct .

THREAD AND INTERRUPT SAFETY

       This  routine is thread-safe.  This means that this routine may be safely used by multiple
       threads without the need for any user-provided thread locks.  However, the routine is  not
       interrupt  safe.   Typically, this is due to the use of memory allocation routines such as
       malloc or other non-MPICH runtime routines that are themselves not interrupt-safe.

NOTES FOR FORTRAN

       All MPI routines in Fortran (except for MPI_WTIME  and  MPI_WTICK  )  have  an  additional
       argument  ierr  at  the  end  of  the  argument list.  ierr is an integer and has the same
       meaning as the  return  value  of  the  routine  in  C.   In  Fortran,  MPI  routines  are
       subroutines, and are invoked with the call statement.

       All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in Fortran.

ERRORS

       All  MPI  routines  (except MPI_Wtime and MPI_Wtick ) return an error value; C routines as
       the value of the function and Fortran routines in the last argument.  Before the value  is
       returned,  the current MPI error handler is called.  By default, this error handler aborts
       the MPI  job.   The  error  handler  may  be  changed  with  MPI_Comm_set_errhandler  (for
       communicators),  MPI_File_set_errhandler  (for files), and MPI_Win_set_errhandler (for RMA
       windows).  The MPI-1 routine MPI_Errhandler_set may be used but  its  use  is  deprecated.
       The  predefined  error  handler  MPI_ERRORS_RETURN may be used to cause error values to be
       returned.  Note that MPI does not guarantee that an  MPI  program  can  continue  past  an
       error; however, MPI implementations will attempt to continue whenever possible.

       MPI_SUCCESS
              - No error; MPI routine completed successfully.

       MPI_ERR_OTHER
              - Other error; use MPI_Error_string to get more information about this error code.

                                            2/22/2022                          MPI_Type_struct(3)