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This script lives in /reg/g/psdmin /sdf/group/lcls/ds/ana/tutorials/examplePythonpsana1_examples/mpiReduce.py and demonstrates how to add arrays distributed across cores (e.g. area detector images) in a parallel MPI job.
Note that this example uses the capitalized "Reduce" method (not "reduce"). This means it works very efficiently with numpy arrays, but is slightly more cumbersome to use.
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Run this
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with
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"mpirun
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-n
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2
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python
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mpiReduce.py":
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from psana import * import numpy as np ds = DataSource('exp=xpptut15:run=54:smd') det = Detector('cspad',ds.env()) from mpi4py import MPI comm = MPI.COMM_WORLD rank = comm.Get_rank() size = comm.Get_size() img = None for nevent,evt in enumerate(ds.events()): if nevent%size!=rank: continue # different ranks look at different events if 'image'img is None: img = det.image(evt).astype(np.double) else: print (f'*{rank}',rank) img += det.image(evt) if nevent>=6: break imgsum = np.empty_like(img) comm.Reduce(img,imgsum) # sum the image across all ranks print ('Rank',: {rank},' sum:', {img.sum()}') if rank==0: print ('Total sum:',imgsum.sum()) MPI.Finalize() |
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