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## Summary¶

Load an event workspace by chunks and compress

## Properties¶

Name

Direction

Type

Default

Description

Filename

Input

string

Mandatory

The name of the Event NeXus file to read, including its full or relative path. The file name is typically of the form INST_####_event.nxs (N.B. case sensitive if running on Linux). Allowed extensions: [‘.nxs.h5’, ‘.nxs’, ‘_event.nxs’]

OutputWorkspace

Output

Workspace

Mandatory

The name of the output EventWorkspace or WorkspaceGroup in which to load the EventNexus file.

MaxChunkSize

Input

number

Optional

Get chunking strategy for chunks with this number of Gbytes. File will not be loaded if this option is set.

CompressTOFTolerance

Input

number

0.01

FilterByTofMin

Input

number

Optional

Optional: To exclude events that do not fall within a range of times-of-flight. This is the minimum accepted value in microseconds. Keep blank to load all events.

FilterByTofMax

Input

number

Optional

Optional: To exclude events that do not fall within a range of times-of-flight. This is the maximum accepted value in microseconds. Keep blank to load all events.

FilterByTimeStart

Input

number

Optional

Optional: To only include events after the provided start time, in seconds (relative to the start of the run).

FilterByTimeStop

Input

number

Optional

Optional: To only include events before the provided stop time, in seconds (relative to the start of the run).

NXentryName

Input

string

Optional: Name of the NXentry to load if it’s not the default.

Input

boolean

False

Load the monitors from the file (optional, default False).

Input

string

If multiple repesentations exist, which one to load. Default is to load the one that is present. Allowed values: [‘’, ‘Events’, ‘Histogram’]

FilterMonByTofMin

Input

number

Optional

Optional: To exclude events from monitors that do not fall within a range of times-of-flight. This is the minimum accepted value in microseconds.

FilterMonByTofMax

Input

number

Optional

Optional: To exclude events from monitors that do not fall within a range of times-of-flight. This is the maximum accepted value in microseconds.

FilterMonByTimeStart

Input

number

Optional

Optional: To only include events from monitors after the provided start time, in seconds (relative to the start of the run).

FilterMonByTimeStop

Input

number

Optional

Optional: To only include events from monitors before the provided stop time, in seconds (relative to the start of the run).

Input

number

95

## Description¶

This is a workflow algorithm that loads an event nexus file in chunks and compresses the resulting chunks before summing them. It uses the algorithms:

## Usage¶

The files needed for this example are not present in our standard usage data download due to their size. They can however be downloaded using these links: PG3_9830_event.nxs.

PG3_9830_event = LoadEventAndCompress(Filename='PG3_9830_event.nxs',
MaxChunkSize=1.)


Example - Usage with MPI

Create a python driver script called test_mpi.py

from mantid.simpleapi import *
import mantid
if AlgorithmFactory.exists('GatherWorkspaces'):
HAVE_MPI = True
from mpi4py import MPI
mpiRank = MPI.COMM_WORLD.Get_rank()
mpiSize = MPI.COMM_WORLD.Get_size()
else:
HAVE_MPI = False
mpiRank = 0 # simplify if clauses
mpiSize = 1 # simplify if clauses

print("Rank =  {} Number of Events =  {}".format(mpiRank, wksp.getNumberEvents()))
if mpiRank == 0:
reduce = AlignAndFocusPowder(InputWorkspace=wksp, CalFileName='PG3_calibrate_d2538_2014_05_13.cal', Params='0.5,0.01,2')


And run it using the following commands

$module load mpi/openmpi-x86_64$ export LD_PRELOAD=/usr/lib64/openmpi/lib/libmpi.so
$mpirun -np 8 python test_mpi.py  to run without mpi is simply $ python test_mpi.py


(you may also need to check out Access Mantid in Python and Notebook)

Categories: AlgorithmIndex | Workflow\DataHandling