13.7. I/O ERROR HANDLING

MPI_File_write_all_begin(fh,...) ;

MPI_File_read_all_begin(fh,...) ;

MPI_File_read_all_end(fh,...) ;

MPI_File_write_all_end(fh,...) ;

since split collective operations on the same le handle may not overlap (see Section 13.4.5, page 421).

13.7 I/O Error Handling

By default, communication errors are fatal|MPI_ERRORS_ARE_FATAL is the default error handler associated with MPI_COMM_WORLD. I/O errors are usually less catastrophic (e.g., \ le not found") than communication errors, and common practice is to catch these errors and continue executing. For this reason, MPI provides additional error facilities for I/O.

Advice to users. MPI does not specify the state of a computation after an erroneous MPI call has occurred. A high-quality implementation will support the I/O error handling facilities, allowing users to write programs using common practice for I/O. (End of advice to users.)

Like communicators, each le handle has an error handler associated with it. The MPI I/O error handling routines are de ned in Section 8.3, page 276.

When MPI calls a user-de ned error handler resulting from an error on a particularle handle, the rst two arguments passed to the le error handler are the le handle and the error code. For I/O errors that are not associated with a valid le handle (e.g., in MPI_FILE_OPEN or MPI_FILE_DELETE), the rst argument passed to the error handler is

MPI_FILE_NULL,

I/O error handling di ers from communication error handling in another important aspect. By default, the prede ned error handler for le handles is MPI_ERRORS_RETURN. The default le error handler has two purposes: when a new le handle is created (by MPI_FILE_OPEN), the error handler for the new le handle is initially set to the default error handler, and I/O routines that have no valid le handle on which to raise an error (e.g., MPI_FILE_OPEN or MPI_FILE_DELETE) use the default le error handler. The defaultle error handler can be changed by specifying MPI_FILE_NULL as the

fh argument to MPI_FILE_SET_ERRHANDLER. The current value of the default le error handler can be determined by passing MPI_FILE_NULL as the fh argument to

MPI_FILE_GET_ERRHANDLER.

Rationale. For communication, the default error handler is inherited from MPI_COMM_WORLD. In I/O, there is no analogous \root" le handle from which default properties can be inherited. Rather than invent a new global le handle, the default le error handler is manipulated as if it were attached to MPI_FILE_NULL. (End of rationale.)

13.8 I/O Error Classes

The implementation dependent error codes returned by the I/O routines can be converted into the error classes de ned in Table 13.3.

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