Programming%20in%20AMPI

1
Programming in AMPI

• Laxmikant Kale
• CS320
• Spring 2003
• Kale_at_cs.uiuc.edu
• http//charm.cs.uiuc.edu
• Parallel Programming Laboratory
• Department of Computer Science
• University of Illinois at Urbana Champaign

2
Virtualization Object-based Parallelization
User is only concerned with interaction between
objects (VPs)
User View
3
Object Arrays

• A collection of data-driven objects
• With a single global name for the collection
• Each member addressed by an index
• sparse 1D, 2D, 3D, tree, string, ...
• Mapping of element objects to procS handled by
  the system

Users view
A0
A1
A2
A3
A..
4
Object Arrays

• A collection of data-driven objects
• With a single global name for the collection
• Each member addressed by an index
• sparse 1D, 2D, 3D, tree, string, ...
• Mapping of element objects to procS handled by
  the system

Users view
A0
A1
A2
A3
A..
System view
A3
A0
5
Object Arrays

• A collection of data-driven objects
• With a single global name for the collection
• Each member addressed by an index
• sparse 1D, 2D, 3D, tree, string, ...
• Mapping of element objects to procS handled by
  the system

Users view
A0
A1
A2
A3
A..
System view
A3
A0
6
Adaptive MPI

• A migration path for legacy MPI codes
• AMPI MPI Virtualization
• Uses Charm object arrays and migratable threads
• Minimal modifications to convert existing MPI
  programs
• Automated via AMPizer
• Based on Polaris Compiler Framework
• Bindings for
• C, C, and Fortran90

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AMPI
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AMPI
Implemented as virtual processors (user-level
migratable threads)
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Writing AMPI programs

• Same as MPI programming, except
• Do not use global variables.
• Why?
• How to
• Move all global variables into a module in f90
• Called globals, for example
• Class or struct in C/C
• Dynamically allocate one instance of globals
• Make any reference to a (former) global variable
  x as
• globalsx (or globals-gtx in C)

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Handling global variables in AMPI

• More refined methods for getting rid of global
  variables
• Esp. when converting existing MPI programs
• Classes of global variables
• Really local (are live only inside subroutines)
• Read-only
• Truly global, but short lived
• Move to functions, and pass as parameters
• Others move to one or more dynamically allocated
  modules

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Load Balancing

• Call load balancer periodically