message passing interface a brief introduction

Experts in numerical software andHigh Performance Computing

Message Passing Interfacea brief introduction

University of Birmingham

30th January 2017

Ning Li - Senior Technical Consultant

Sally Bridgwater – HPC Application Analyst

2High Performance Computing Consulting | Numerical Algorithms | Software Engineering Services | www.nag.com


Best domain decomposition is dependent on algorithm.


3rd party partitioning software often required


A subset of processes responsible for each model

Atmospheric Model

Hydrology

Model

Ocean

Model

Land Surface Model


From: source rankLetter # 1234 (tag)

To: destination rank

The message has:

A type - integer, real, etc.

A count

A location – memory address

Both source and destination

ranks need to provide these

Please send count number data of this type, located at memory address a on the source rank, to the destination rank and write to memory address b there.


MPI_Recv()

MPI_Send()

Process 0

MPI_Recv()

MPI_Send()

Process 1

Tim

e


MPI_Barrier

Tim

eT


Root

10010110

0

10010110

2

10010110

1

10010110

Size-1

10010110


Proc 0

01101

Proc 1

10101

Proc 2

11001

Proc 3

01011

Proc 4

11101

01101 10101 11001 01011 11101


Basic datatype

col_type: a derived datatype that is strided

row_type: a derived datatype that is contiguous


Rank=0

Coord=(0,0)

Rank=1

Coord=(0,1)

Rank=2

Coord=(0,2)

Rank=3

Coord=(1,0)

Rank=4

Coord=(1,1)

Rank=5

Coord=(1,2)


Experts in High Performance Computing, Algorithms and Numerical Software Engineering

www.nag.com | blog.nag.com | @NAGtalk

message passing interface a brief introduction

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