tailieunhanh - Parallel Programming: for Multicore and Cluster Systems- P26

Parallel Programming: for Multicore and Cluster Systems- P26: Innovations in hardware architecture, like hyper-threading or multicore processors, mean that parallel computing resources are available for inexpensive desktop computers. In only a few years, many standard software products will be based on concepts of parallel programming implemented on such hardware, and the range of applications will be much broader than that of scientific computing, up to now the main application area for parallel computing | 242 5 Message-Passing Programming The parameter command specifies the name of the program to be executed by each of the processes argv contains the arguments for this program. In contrast to the standard C convention argv 0 is not the program name but the first argument for the program. An empty argument list is specified by MPI_ARGV_NULL. The parameter maxprocs specifies the number of processes to be started. If the MPI runtime system is not able to start maxprocs processes an error message is generated. The parameter info specifies an data structure with key value pairs providing additional instructions for the MPI runtime system on how to start the processes. This parameter could be used to specify the path of the program file as well as its arguments but this may lead to non-portable programs. Portable programs should use MPI_INFO_NULL. The parameter root specifies the number of the root process from which the new processes are spawned. Only this root process provides values for the preceding parameters. But the function MPLCom spawnf is a collective operation . all processes belonging to the group of the communicator comm must call the function. The parameter intercomm contains an intercommunicator after the successful termination of the function call. This intercommunicator can be used for communication between the original group of comm and the group of processes just spawned. The parameter errcodes is an array with maxprocs entries in which the status of each process to be spawned is reported. When a process could be spawned successfully its corresponding entry in errcodes will be set to . Otherwise an implementation-specific error code will be reported. A successful call of MPLCom spawnf starts maxprocs identical copies of the specified program and creates an intercommunicator which is provided to all calling processes. The new processes belong to a separate group and have a separate communicator comprising all .

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