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Hotspots of computing move over the time. Causing load imbalance.
Wrapping around if not enough PEs
Forum founded in 1993, released Standard 1.0 in 1994, 1.1 in 1995, 2 in 1997 by vote.
Our dept head Marc Snir is a major contributor to the standard!
Status containing error info for (potentially) multiple requests.
C++ binding is not mentioned till 2.0.
C++ binding is not mentioned till 2.0.
Number of chares:
Independent of number of processors
Typically larger than number of processors
Seeking optimal division of labor between system and programmer:
Decomposition done by programmer, everything else like mapping and scheduling is automated
Implemented as virtual processors (user-level migratable threads)
27, 64, 125, 216, 512
Two points in comparison:
1.Performance is slightly worse:
  1) we are running on top of MPI
  2) remember more advantages AMPI are not used here.
2. Number of processors flexibility
Some overhead of offset by the caching effect, etc.
Version includes your communication network and OS
Charmc-options like -g
Example of two threads sharing one counter.
A sets it to 2, B increments it, A reads the incorrect count.
Isomalloc: special memory allocation mode, give allocated memory the same virtual address on all processors.   problem: address space limitation on 32-bit machines. 4GB – OS, conventional heap allocation, = virtual address ~1GB
  divided over 20PE -> 50MB per PE
Example of two threads sharing one counter.
A sets it to 2, B increments it, A reads the incorrect count.
Isomalloc: special memory allocation mode, give allocated memory the same virtual address on all processors.   problem: address space limitation on 32-bit machines. 4GB – OS, conventional heap allocation, = virtual address ~1GB
  divided over 20PE -> 50MB per PE
Example of two threads sharing one counter.
A sets it to 2, B increments it, A reads the incorrect count.
Isomalloc: special memory allocation mode, give allocated memory the same virtual address on all processors.   problem: address space limitation on 32-bit machines. 4GB – OS, conventional heap allocation, = virtual address ~1GB
  divided over 20PE -> 50MB per PE
Avoid large stack data allocation because stack size in AMPI is fixed and doesn’t grow at run time.
Can be specified with command line option.
Can use stack space by removing pointer and ALLOCATE, but limited stacksize
Avoid large stack data allocation because stack size in AMPI is fixed and doesn’t grow at run time.
Can be specified with command line option.
Informs the load balancing system that you are ready to be migrated, if needed. If the system decides to migrate you, the pup function passed to TCharm Register will first be called with a sizing pupper, then a packing, deleting pupper. Your stack and pupped data will then be sent to the destination machine, where your pup function will be called with an unpacking pupper. TCharm Migrate will then return. Can only be
called from in the parallel context.
Isomalloc: special memory allocation mode, give allocated memory the same virtual address on all processors.   problem: address space limitation on 32-bit machines. 4GB – OS, conventional heap allocation, = virtual address ~1GB
  divided over 200PE -> 50MB per PE
Isomalloc: special memory allocation mode, give allocated memory the same virtual address on all processors.   problem: address space limitation on 32-bit machines. 4GB – OS, conventional heap allocation, = virtual address ~1GB
  divided over 200PE -> 50MB per PE
Isomalloc: special memory allocation mode, give allocated memory the same virtual address on all processors.   problem: address space limitation on 32-bit machines. 4GB – OS, conventional heap allocation, = virtual address ~1GB
  divided over 200PE -> 50MB per PE
Powerful idea used in Charm++, now applied to AMPI too.
First this idea of non-blocking collectives was implemented in IBM MPI, but as AMPI is based on threads and capable of migration, it has more flexibility to take advantage of the overlapping feature.
Mention specially designed 2d fft.
but is that possible?
Powerful idea used in Charm++, now applied to AMPI too.
First this idea of non-blocking collectives was implemented in IBM MPI, but as AMPI is based on threads and capable of migration, it has more flexibility to take advantage of the overlapping feature.
DON’T SAY the amount of reduced is equal to the amount of overlapped