Parallelism

SMP stands for Shared Memory Parallelism.

This version is based on shared memory architecture of computers.

For this kind of computer, all processors can access to a common memory space. Each process can access to all memory allocated by the program.

Figure 1.

Depending on the operating system, this version will be able to use up to 8, 12 or 16 processors with a reasonable efficiency. The efficiency can be considered as an acceptable one if it is greater than 50% (that is to say, the speedup is greater than half the number of processors).

SPMD stands for “Single Program Multiple Data”.

Radioss Starter divides the model into several domains (equal to number of processors asked for).

Up to Radioss Version 4

The data is next sent to each process in Radioss Engine; this is the “Parallel Initialization”. The first process reads the complete RESTART file, sending the data to each other process.

Some additional memory is needed on first process for this operation in this version.

From Radioss Version 5.1:

Radioss Starter writes as many RESTART files as the number of processes which will be used for the run. Each RESTART file is built from only the data that will be needed by the relative process, and is read directly by this process when running Radioss Engine. Additional memory is no longer needed for the “Parallel Initialization”.

Then each program executes on each domain. The management of computation at the frontiers of the domains remains and the necessity to communicate some information between the processes is implemented through the use of the MPI 'Message Passing Interface'.

This SPMD version is free from the computer architecture. It can run on distributed memory machines, shared memory machines, workstations cluster or high performance computation cluster.

With this version it is possible to use more processors than with the SMP version, with a better efficiency. It becomes possible to use more than 128 cores with a good speedup.

Figure 2.