.TH MPI_Type_indexed 3 "11/12/2019" " " "MPI"

.SH NAME

MPI_Type_indexed \-  Creates an indexed datatype 

.SH SYNOPSIS

.nf

int MPI_Type_indexed(int count,

const int *array_of_blocklengths,

const int *array_of_displacements,

MPI_Datatype oldtype, MPI_Datatype * newtype)

.fi

.SH INPUT PARAMETERS

.PD 0

.TP

.B count 

- number of blocks -- also number of entries in array_of_displacements and array_of_blocklengths

.PD 1

.PD 0

.TP

.B array_of_blocklengths 

- number of elements in each block (array of nonnegative integers)

.PD 1

.PD 0

.TP

.B array_of_displacements 

- displacement of each block in multiples of oldtype (array of

integers)

.PD 1

.PD 0

.TP

.B oldtype 

- old datatype (handle)

.PD 1

.SH OUTPUT PARAMETERS

.PD 0

.TP

.B newtype 

- new datatype (handle)

.PD 1

.SH 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 

.I malloc

or other non-MPICH runtime routines that are themselves not interrupt-safe.

.SH NOTES FOR FORTRAN

All MPI routines in Fortran (except for 

.I MPI_WTIME

and 

.I MPI_WTICK

) have

an additional argument 

.I ierr

at the end of the argument list.  

.I 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

.I call

statement.

All MPI objects (e.g., 

.I MPI_Datatype

, 

.I MPI_Comm

) are of type 

.I INTEGER

in Fortran.

The array_of_displacements are displacements, and are based on a zero origin.  A common error

is to do something like to following

.nf

integer a(100)

integer array_of_blocklengths(10), array_of_displacements(10)

do i=1,10

array_of_blocklengths(i)   = 1

10       array_of_displacements(i) = 1 + (i-1)*10

call MPI_TYPE_INDEXED(10,array_of_blocklengths,array_of_displacements,MPI_INTEGER,newtype,ierr)

call MPI_TYPE_COMMIT(newtype,ierr)

call MPI_SEND(a,1,newtype,...)

.fi

expecting this to send "a(1),a(11),..." because the array_of_displacements have values

"1,11,...".   Because these are 

.B displacements

from the beginning of "a",

it actually sends "a(1+1),a(1+11),...".

If you wish to consider the displacements as array_of_displacements into a Fortran array,

consider declaring the Fortran array with a zero origin

.nf

integer a(0:99)

.fi

.SH ERRORS

All MPI routines (except 

.I MPI_Wtime

and 

.I 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 

.I MPI_Comm_set_errhandler

(for communicators),

.I MPI_File_set_errhandler

(for files), and 

.I MPI_Win_set_errhandler

(for

RMA windows).  The MPI-1 routine 

.I MPI_Errhandler_set

may be used but

its use is deprecated.  The predefined error handler

.I MPI_ERRORS_RETURN

may be used to cause error values to be returned.

Note that MPI does 

.B not

guarentee that an MPI program can continue past

an error; however, MPI implementations will attempt to continue whenever

possible.

.PD 0

.TP

.B MPI_ERR_COUNT 

- Invalid count argument.  Count arguments must be 

non-negative; a count of zero is often valid.

.PD 1

.PD 0

.TP

.B MPI_ERR_TYPE 

- Invalid datatype argument.  Additionally, this error can

occur if an uncommitted MPI_Datatype (see 

.I MPI_Type_commit

) is used

in a communication call.

.PD 1

.PD 0

.TP

.B MPI_ERR_ARG 

- Invalid argument.  Some argument is invalid and is not

identified by a specific error class (e.g., 

.I MPI_ERR_RANK

).

.PD 1

.PD 0

.TP

.B MPI_ERR_INTERN 

- This error is returned when some part of the MPICH 

implementation is unable to acquire memory.  

.PD 1