multithreading not working properly
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- Dominant language
- C++
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Description
I run SPECT and PET reconstruction using MPI and openMP with the following problems:
openMP: seems to be much slower when I use more threads both with PET and SPECT data
MPI: if I set "Enable distributed caching:=1" I get the following:
INFO: Computing sensitivity
INFO: Sending segment 0, view 0 to slave 1
INFO: Sending segment 0, view 20 to slave 2
INFO: Sending segment 0, view 40 to slave 3
WARNING: ProjDataFromStream::set_viewgram: error after seekp
ERROR: Slave 2: Storing viewgrams failed!
INFO: Sending segment 0, view 60 to slave 4
WARNING: ProjDataFromStream::set_viewgram: error after seekp
INFO: Sending segment 0, view 80 to slave 5
ERROR: Slave 3: Storing viewgrams failed!
if it is set to zero I achieve around a factor 4 acceleration with 10 threads. If I use more I do not get further acceleration (This also for SPECT and PET).
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Research direction
No source files, tests, or entry points are named. Start by reproducing both the OpenMP scaling behavior and the MPI failure with distributed caching enabled, using the reported reconstruction settings and log messages; done means the failures and scaling limit are diagnosed and corrected with verification for PET and SPECT.
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Assessment
- Tech stack
- cpp
- Domain
- distributed-systems, hpc, performance
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 25/100