Baisc knowlodges of parallel computing
Two familers of parallel machines
Shared-memory architecture
These parallel machines are build up on a set of processors which have access to a common memory. Usually the name of SMP machines is used for computers based on this architecture, where SMP stands for Symmetric Multi Processing.
Distributed-memory architecture
In these parallel machines each processor has its own private memory and information is interchanged between the processors through messages. The name of clusters is commonly used for this type of computing devices.
OpenMP
A new industry standard has been created with the aim to serve as a good basis for the development of parallel programs on shared-memory machines.
Open the directives of OpenMP and conditional compliation
!$OMP
!$
!$OMP: The OpenMP-compliant compiler knows that the following information in the line is an OpenMP directive.
!$: The corresponding line is said to be affected by a conditional compilation. When execution start, these two characters ! and $ will be replaced by two white spaces so that the compiler is taking into account the line
Parallel regions
!$OMP PARALLEL
!$OMP END PARALLEL
OpenMP constructs
!$OMP DO
do i = 1, 1000
...
enddo
!$OMP END DO
