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The Message-Passing Interface (MPI) was designed to be an industrial-strength message-passing environment that is portable across a wide range of hardware environments.

Much like High Performance FORTRAN, MPI was developed by a group of computer vendors, application developers, and computer scientists. The idea was to come up with a specification that would take the strengths of many of the existing proprietary message passing environments on a wide variety of architectures and come up with a specification that could be implemented on architectures ranging from SIMD systems with thousands of small processors to MIMD networks of workstations and everything in between.

Interestingly, the MPI effort was completed a year after the High Performance FORTRAN (HPF) effort was completed. Some viewed MPI as a portable message-passing interface that could support a good HPF compiler. Having MPI makes the compiler more portable. Also having the compiler use MPI as its message-passing environment insures that MPI is heavily tested and that sufficient resources are invested into the MPI implementation.

Pvm versus mpi

While many of the folks involved in PVM participated in the MPI effort, MPI is not simply a follow-on to PVM. PVM was developed in a university/research lab environment and evolved over time as new features were needed. For example, the group capability was not designed into PVM at a fundamental level. Some of the underlying assumptions of PVM were based “on a network of workstations connected via Ethernet” model and didn’t export well to scalable computers. One should not diminish the positive contributions of PVM, however. PVM was the first widely avail- able portable message-passing environment. PVM pioneered the idea of heterogeneous distributed computing with built-in format conversion. In some ways, MPI is more robust than PVM, and in other ways, MPI is simpler than PVM. MPI doesn’t specify the system management details as in PVM; MPI doesn’t specify how a virtual machine is to be created, operated, and used.

Mpi features

MPI has a number of useful features beyond the basic send and receive capabilities. These include:

  • : A communicator is a subset of the active processes that can be treated as a group for collective operations such as broadcast, reduction, barriers, sending, or receiving. Within each communicator, a process has a rank that ranges from zero to the size of the group. A process may be a member of more than one communicator and have a different rank within each communicator. There is a default communicator that refers to all the MPI processes that is called MPI_COMM_WORLD .
  • : A communicator can have a topology associated with it. This arranges the processes that belong to a communicator into some layout. The most common layout is a Cartesian decomposition. For example, 12 processes may be arranged into a 3×4 grid. Sounds a little like HPF, no? Once these topologies are defined, they can be queried to find the neighboring processes in the topology. In addition to the Cartesian (grid) topology, MPI also supports a graph-based topology.
  • : MPI supports multiple styles of communication, including blocking and non- blocking. Users can also choose to use explicit buffers for sending or allow MPI to manage the buffers. The nonblocking capabilities allow the overlap of communication and computation. MPI can support a model in which there is no available memory space for buffers and the data must be copied directly from the address space of the sending process to the memory space of the receiving process. MPI also supports a single call to perform a send and receive that is quite useful when processes need to exchange data.
  • : Some of the calls in MPI automate collective operations in a single call. For example, the broadcast operation sends values from the master to the slaves and receives the values on the slaves in the same operation. The net result is that the values are updated on all processes. Similarly, there is a single call to sum a value across all of the processes to a single value. By bundling all this functionality into a single call, systems that have support for collective operations in hardware can make best use of this hardware. Also, when MPI is operating on a shared-memory environment, the broadcast can be simplified as all the slaves simply make a local copy of a shared variable.

Questions & Answers

A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
Aislinn Reply
cm
tijani
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John Reply
what is physics
Siyaka Reply
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Jude Reply
Can you compute that for me. Ty
Jude
what is the dimension formula of energy?
David Reply
what is viscosity?
David
what is inorganic
emma Reply
what is chemistry
Youesf Reply
what is inorganic
emma
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
please, I'm a physics student and I need help in physics
Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
Krampah Reply
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
Sahid Reply
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
Samuel Reply
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Joseph Reply
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
Ryan
what's motion
Maurice Reply
what are the types of wave
Maurice
answer
Magreth
progressive wave
Magreth
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Muhammad Reply
fine, how about you?
Mohammed
hi
Mujahid
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
yasuo Reply
Who can show me the full solution in this problem?
Reofrir Reply
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Source:  OpenStax, High performance computing. OpenStax CNX. Aug 25, 2010 Download for free at http://cnx.org/content/col11136/1.5
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