Degrees of
Parallelism
The
number of parallel execution servers associated with a single operation is
known as the degree of parallelism(DOP).
We
can apply parallelism only when the problem broken into discrete pieces to be
solved simultaneously.
Types of parallelism
1.
Data Level Parallelism
It is parallelization across
multiple processors in parallel computing environments.
For eg., if we want to sum of
array elements in sequential execution, the time taken by the process is n*Ta .
If we want to execute the same job as a data parallel job on 4 processors the
time taken would reduce to (n/4)*Ta+merging overhead time units.
2.
Task Level Parallelism
It covers the execution of
computer programs across multiple processors on same or multiple machines. For eg., task parallelism would be an
application creating thread for doing parallel processing where each thread is
responsible for performing a different operation.
3.
Instruction Level Parallelism
It is a measure of how many of
the instructions in a computer program can be executed simultaneously.
For eg., a=b+c, d=e+f, x=a+b
Out of these three instructions,
two instructions executed individually. The third one depends on the result of
first and second operations.
4.
Bit Level Parallelism
It is a form of parallel
computing based on increasing processor word size. Increasing the word size
reduces the number of instructions the processor must execute in order to
perform an operation on variables whose sizes are greater than the length of
the word.
