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       The MPI standard originally made vague statements about padding and alignment; this was intended to allow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.

                                                    2/9/2024                                  MPI_Type_struct(3)