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NAME

MPI_Type_lb - Returns the offset of the lower bound of a type in bytes

SYNOPSIS

#include <mpi.h> int MPI_Type_lb(MPI_Datatype datatype , MPI_Aint *lb );

#include <pmpi.h> int PMPI_Type_lb(MPI_Datatype datatype , MPI_Aint *lb );

INCLUDE 'mpif.h' MPI_TYPE_LB(datatype , lb , ierr ) INTEGER datatype , lb , ierr

INPUT PARAMETER

datatype - type (handle)

OUTPUT PARAMETER

lb - offset of the lower bound (integer).

DESCRIPTION

The MPI_Type_lb() function is used to determine the offset of the lower bound of a type datatype . Note that it is possible to alter the upper and lower bounds through the use of the MPI_UB and MPI_LB types in constructing a user defined type. Thus this "effective" lower bound may not correspond to the actual lower bound of memory accessed by users of this type.

The FORTRAN version of this function will return a 32-bit value for the lower-bound. Due to this, this function is deprecated by the MPI committee. Instead, use the MPI_Type_get_true_extent() function, which will return the full 64-bit value.

PMPI_Type_lb() is the profiling version of this function.

ERRORS

All MPI routines except for MPI_Wtime and MPI_Wtick return an error code. The the current MPI error handler is invoked if the return value is not MPI_SUCCESS. The default error handler aborts, but this may be changed with by using the MPI_Errhandler_set() function. The predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned instead. Note that MPI does not guarentee that an MPI program can continue past an error. In this implementation, all errors except MPI_ERR_INTERN or MPI_ERR_OTHER should always be recoverable.

In C, the error code is passed as the return value. In FORTRAN, all functions have an parameter ierr which returns the error code. MPI C++ functions do not directly return an error code. However, C++ users may want to use the MPI::ERRORS_THROW_EXCEPTIONS handler. This will throw an MPI::Exception with the corresponding error code. To prevent exceptions from being raised from within C and Fortran code, they will see all error return values as MPI_ERR_PENDING when this handler is chosen. In this implementation, call MPI::throw_exception() to throw the correct exception if this occurs.

MPI_SUCCESS - No error;

MPI_ERR_PENDING - Pending exception;

MPI_ERR_TYPE - Invalid data type;

MPI_ERR_ARG - Invalid pointer.

SEE ALSO

MPI_Type_size (3) MPI_Type_ub (3) MPI_Type_extent (3) MPI_Type_get_true_extent (3) MPI_Type_free (3) MPI_Type_commit (3)

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