Mpi functions and environment, Computer Networking

Assignment Help:

MPI contains hundreds of functions, a small subset of which is enough for most practical purposes. We shall talk about some of them in this unit.

Functions for MPI Environment:

int MPI_Init ( int *argc, char ** argv)

    It initializes the MPI environment. By that, No MPI function can be called before MPI_Init.

int MPI_Finalize (void)

It stops the MPI environment.  No MPI function can be called after MPI_Finalize. Each MPI process belongs to one or more groups (also known as communicator). Every process is recognized by its rank (0 to group size -1) within the given group. Initially, all processes belong to a default group known as MPI_COMM_WORLD group. Additional groups can be produced by the user as and when needed.  Now, we shall learn some functions related to communicators.

int MPI_Comm_size (MPI_Comm comm,  int *size)

returns variable size that have number of processes in group comm.

int MPI_Comm_rank (MPI_Comm comm,  int *rank)

returns rank of calling process in group comm.

Functions for Message Passing:

MPI processes cannot share memory space and single process cannot directly access other process's variables. Therefore, they need some type of communication between themselves. In MPI environment this communication is in the kind of message passing. A message in MPI has the following fields:

msgaddr: It can be each address in the sender's address space and refers to location in memory where message data begins.

count:  Number of occurrence of data items of message datatype obtained in message.

datatype:  Type of data in message. This field is beneficial in the sense that MPI supports heterogeneous computing and the different nodes may interpret count field differently. For example, if the message have a strings of 2n characters (count =2n), some machines may interpret it have 2n characters and some containing n characters depending upon the storage allocated per character (1 or 2). The basic datatype in MPI having of all basic parts in C and Fortran with two additional types namely MPI_BYTE and MPI_PACKED. MPI_BYTE denotes a byte of 8 bits.

dest or source : Receiving process or Rank of sending in communicator.

tag: Identifier for definite message or type of message. It let the programmer to deal with the arrival of message in an orderly way, even if the arrival of the message is not orderly.

comm.: Communicator. It is an group of a process and object wrapping context .It is allocated by system instead of user.

The functions used for messaging passing are:

int MPI_Send(void *msgaddr, int count,  MPI_Datatype datatype, int dest, int tag, MPI_Comm comm.)

on return, msg can be reused instantly.

int MPI_Recv(void *msgaddr, int count,  MPI_Datatype datatype, int dest, int tag, MPI_Comm comm.)

on return, msg contains requested message.

MPI message passing may be either collective or point-to-point.


Related Discussions:- Mpi functions and environment

Sharing information - network layer and routing , Sharing  information  ...

Sharing  information  To understand  how distance vector routing  works examine the  internet shown in  the  clouds represents local  area network . the  number  inside each c

What is unbound transmission media, Unbound Transmission Media Unbound ...

Unbound Transmission Media Unbound transmission media extend beyond the limiting confines of cabling. They give a good communication alternative for WANS. The lack of physical

Explain 100base-tx, 100Base-TX Uses two category 5 UTP cable pairs...

100Base-TX Uses two category 5 UTP cable pairs or else two STP cable pairs to connect stations to a hub (star) One pair holds frames from station to hub one pair from

Hardware component used to store buffers, Recognize the hardware component ...

Recognize the hardware component used to store buffers, tables, running-configuration etc? Ans) RAM is the dynamic memory area. ROM have the boot strap code, NVRAM have the star

Chord, how to implement chord connection as the network management system ?...

how to implement chord connection as the network management system ?

Dynamic process groups in parallel virtual machine , Dynamic Process Groups...

Dynamic Process Groups To generate and manage dynamic groups, a separate library libgpvm3.a must be connected with the user programs that make use of any of the set functions.

Transmission robustness and security, Transmission robustness and security ...

Transmission robustness and security Unless properly designed, a wireless LAN might be interference prone and simply eavesdropped. The design of a wireless LAN must allow relia

Explain typical network topologies, Question: a) Explain briefly three ...

Question: a) Explain briefly three typical network topologies giving one advantage and one disadvantage of each topology. Explain the three topologies with appropriate diagrams

Define carrier sense multiple access collision avoidance, Carrier Sense Mul...

Carrier Sense Multiple Access/Collision Avoidance a) Necessary since wireless LANs cannot implement CSMA/CD b) Collision detection requires increased bandwidth requirements

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd