CreateMDWorkspace v1¶

Summary¶

Creates an empty MDEventWorkspace with a given number of dimensions.

Properties¶

Name	Direction	Type	Default	Description
Dimensions	Input	number	1	Number of dimensions that the workspace will have.
EventType	Input	string	MDLeanEvent	Which underlying data type will event take. Allowed values: [‘MDEvent’, ‘MDLeanEvent’]
Extents	Input	dbl list		A comma separated list of min, max for each dimension, specifying the extents of each dimension.
Names	Input	str list		A comma separated list of the name of each dimension.
Units	Input	str list		A comma separated list of the units of each dimension.
Frames	Input	str list		A comma separated list of the frames of each dimension. The frames can be General Frame: Any frame which is not a Q-based frame. QLab: Wave-vector converted into the lab frame. QSample: Wave-vector converted into the frame of the sample. HKL: Wave-vector converted into the crystal’s HKL indices. Note if nothing is specified then the General Frame is being selected. Also note that if you select a frame then this might override your unit selection if it is not compatible with the frame.
SplitInto	Input	int list	5	A comma separated list of into how many sub-grid elements each dimension should split; or just one to split into the same number for all dimensions. Default 5.
SplitThreshold	Input	number	1000	How many events in a box before it should be split. Default 1000.
MaxRecursionDepth	Input	number	5	How many levels of box splitting recursion are allowed. The smallest box will have each side length Default 5.
MinRecursionDepth	Input	number	0	Optional. If specified, then all the boxes will be split to this minimum recursion depth. 0 = no splitting, 1 = one level of splitting, etc. Be careful using this since it can quickly create a huge number of boxes = (SplitInto ^ (MinRercursionDepth * NumDimensions)).
OutputWorkspace	Output	Workspace	Mandatory	Name of the output MDEventWorkspace.
Filename	Input	string		Optional: to use a file as the back end, give the path to the file to save. Allowed extensions: [‘.nxs’]
Memory	Input	number	-1	If Filename is specified to use a file back end: The amount of memory (in MB) to allocate to the in-memory cache. If not specified, a default of 40% of free physical memory is used.

Description¶

This algorithm creates an empty MDEventWorkspace from scratch. The workspace can have any number of dimensions (up to ~20). Each dimension must have its name, units, extents specified as comma-spearated string.

The SplitInto parameter determines how splitting of dense boxes will be performed. For example, if SplitInto=5 and the number of dimensions is 3, then each box will get split into 5x5x5 sub-boxes.

The SplitThreshold parameter determines how many events to keep in a box before splitting it into sub-boxes. This value can significantly affect performance/memory use! Too many events per box will mean unnecessary iteration and a slowdown in general. Too few events per box will waste memory with the overhead of boxes.

You can create a file-backed MDEventWorkspace by specifying the Filename and Memory parameters.

Usage¶

Example

mdws = CreateMDWorkspace(Dimensions=3, Extents='-10,10,-10,10,-10,10', Names='A,B,C', Units='U,U,U')

print("mdws is a " + mdws.id())
print("with {0} dimensions:".format(mdws.getNumDims()))
for i in range (mdws.getNumDims()):
    print(mdws.getDimension(i).name)

Output:

mdws is a MDEventWorkspace<MDLeanEvent,3>
with 3 dimensions:
A
B
C

Categories: AlgorithmIndex | MDAlgorithms\Creation

Source¶

C++ source: CreateMDWorkspace.cpp (last modified: 2019-07-17)

C++ header: CreateMDWorkspace.h (last modified: 2018-10-05)