|
hyPACK-2013 : Parallel Prog. Using Threaded I/O & MPI I/O |
|
Simple programs using MPI 2 I/O library calls and threaded I/O programs are executed on Message Passing
Cluster or Multi-Core Processor Systems that support MPI library.
|
|
|
|
Example 1.1
|
Write a simple MPI I/O program performing sequential I/O to multiple files
|
|
Example 1.2
|
Write a Pthread I/O program performing each thread writing to separate file
( Assignment )
|
|
Example 1.3
|
Write an MPI program performing MPI I/O to separate files (Using MPI 2.0)
|
|
Example 1.4
|
Write an MPI program performing MPI I/O to single file (Using MPI 2.0)
|
|
Example 1.5
|
Write an Pthread I/O program reading the file with different number of threads.
( Assignment )
|
|
Example 1.6
|
Write a MPI I/O program to read the file with different number of processes. (Using MPI 2.0)
|
|
Description of Threaded & MPI 2.0 I/O Programs on Multi-Core Processors |
Objective
Description
This is a very simple program to get the feel of how threads perform sequential I/O.
For simplicity,we use MPI Basic library calls.
we assume the each process has set of n integers of the array with total length depends
upon on how many processes there are. Each process has block of integers in each process's memory and
each process writes to an appropriate location of global array.
The program begins with each process initializing its portion of the array. All process except first
process writes data. The first process writes its data and reads all the data form other process
and first process write the data to file.
Input
Output
|
Example 1.2 :
Write a Pthread I/O program performing each thread writing to separate file
|
Objective
Description
In this example, thread parallelism is introduced. Each thread writes to separate file thus, enabling parallel
data transfer.. For simplicity,
we assume the each thread has set of n integers of the array with total length depends
upon on how many threads there are. Each thread has block of integers in each thread's memory and
each thread writes to separate file. Each thread opens file, writes to it, and closes it. Written files
are separated by appending each thread id to the name of its output file. Here, the I/O
operations can take place in parallel but set of files are in use instead of a single file.
The flow of writing data files have advantages and dis-advantages which merely depends upon
nature of application. The application requirements such as (a). need of one file in which all the
files may have to be joined together in specific order, (b). All the threads may concurrently read these
files, and (c). Keep track of number of files as a group for moving them, or copying them or sending
them across a network.
Input
Output
|
Example 1.3 :
Write an MPI program performing MPI I/O (Writing) to separate files (Using MPI 2.0)
( Download source code :
mpi-io-multiple-files.c )
|
Objective
Description
This example show how familiar I/O operations look in MPI 2.0.
MPI 2.0 I/O Library calls is used in this example. Each process writes to separate files in parallel
using MPI 2.0 library calls. thus, enabling parallel
data transfer.. For simplicity,
we assume the each process has set of n integers of the array with total length depends
upon on how many process p there are. Each process has block of integers in each process
memory and
each process writes to separate file. Each process opens file, writes to it, and closes it.
Written files
are separated by appending each process's rank to the name of its output file. Here, the I/O
operations can take place in parallel but set of files are in use instead of a single file.
The declaration of FILE, open, close, write is done using
MPI functions.
The flow of writing data files have advantages and dis-advantages which merely depends upon
nature of application. The application requirements such as (a). need of one file in which all the
files may have to be joined together in specific order, (b). All the threads may concurrently read these
files, and (c). Keep track of number of files as a group for moving them, or copying them or sending
them across a network. The MPI program is easy to understand and from performance point of view,
the quantification of MPI I/O overheads is required.
MPI_COMM_SELF library call is used and it indicates that only one process is involved
while opening the file.
Input
Output
|
Example 1.4 :
Write an MPI program performing MPI I/O to single file (Using MPI 2.0).
( Download source code :
mpi-io-write-single-file.c )
|
Objective
Description
MPI process share a single file instead of the writing to separate files, thus avoiding the
having multiple files as discussed on example 1.3. This shows performance advantages of parallelism adopted using MPI.
The new library calls of MPI are used to sharing a a file among processes. Here,
MPI_COMM_WORLD library call is used instead of
MPI_COMM_SELF library call. This indicates that all the processes are opening a
single file together and it is a collective operations on the communicator, on all
participating process.
Input
The input file holding the square matrix (Number of Rows, Columns of the matrix)
Output
|
Example 1.5 :
Write an Pthread I/O program reading the file with different number of threads
|
Objective
Description
This example demonstrates how to read a file involving all the threads.
All the participating threads globally share the input data file and all the threads concurrently
read a portion of the data file.
We assume the each thread read set of n/p integers of the array in which the input data
file size is of n is globally accessible by all p threads. We assume that
n is divisible by p
Each thread writes the output data which consists of block of integers Here, the I/O
operations can take place in parallel but set of files written by each thread.
Input
Output
|
Example 1.6 :
Write a MPI I/O program to read a file with different no. of processes (Using MPI 2.0)
( Download source code :
mpi-io-multiple-files.c )
|
Objective
Description
This example program demonstrates reading of a file involving all the MPI process. The
program is independent of the number of processes that run it.
The new MPI library call
MPI_File_get_size library call is used to know about the size of the file which is stored
in bytes. MPI defines a type
MPI_Offset , that is large enough to contain a file size. Each process writes the contents
of reading file.
Input
Each Process Output file.
|
| |
|
|
