Charm overview

1
Charm overview

• L. V. Kale

2
Parallel Programming tasks

• Decomposition (what to do in parallel)
• Mapping
• Scheduling (sequencing)
• Machine dependent expression

3
Spectrum of parallel Languages
Leve l
MPI
Specialization
4
Charm

• Data Driven Objects
• Asynchronous method invocation
• Object Arrays
• Object Groups
• global object with a representative on each PE
• Prioritized scheduling

5
Data Driven Execution
Scheduler
Scheduler
Message Q
Message Q
6
Chares (Data driven Objects)

• Regular C classes,
• with some methods designated as remotely
  invokable (called entry methods)
• entry methods have only one parameter of type
  message
• Creation
• CProxy_CckNew(msg)
• Creates an instance of C on some pe
• CProxy_CckNew(msg, pe)

7
Messages

• A user-defined C class
• inherits from a system-defined class
• messages can be communicated to others as
  parameters
• Has regular data fields
• Declaration normal C,
• inherit from a system defined class
• Creation (just usual C)
• MsgType m new MsgType

8
Remote method invocation

• Proxy Classes
• For each chare class, the system generates a
  proxy class. (C CProxy_C)
• Each chare has a global ID (ChareID)
• thishandle (analogous to this)
• You can send thishandle in messages
• Given a handle h, you can create a proxy
• CProxy_C p(h) // or q new CProxy_C(h)
• p.method(msg) // or q-gtmethod(msg)

9
Object Groups

• A group of objects (chares)
• with exactly one representative on each processor
• A single Id for the group as a whole
• invoke methods in a branch (asynchronously), all
  branches (broadcast), or in the local branch
• creation
• groupId CProxy_CckNew(msg)
• remote invocation
• CProxy_C p(groupId)
• p.methodName(msg) // p.methodName(msg, peNum)
• p.LocalBranch-gtf(.)

10
CkChareID mainhandle mainmain(CkArgMsg m)
int i, low 0 for (i0 ilt100 i)
new CProxy_piPart() responders 100 count
0 mainhandle thishandle // readonly
initialization void mainresults(DataMsg
msg) count msg-gtcount if (0
--responders) CkPrintf("pi f \n",
4.0count/100000) CkExit()
11
piPartpiPart() // declarations..
srand48((long) this) mySamples 100000/100
for (i 0 ilt mySamples i) x
drand48() y drand48() if ((xx yy)
lt 1.0) localCount DataMsg result
new DataMsg result-gtcount localCount
CProxy_main mainproxy(mainhandle)
mainproxy.results(result) delete this