CreateMDWorkspace v1

../_images/CreateMDWorkspace-v1_dlg.png

CreateMDWorkspace dialog.

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 l = (extents) / (SplitInto^{MaxRecursionDepth}). 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).getName()

Output:

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

Categories: Algorithms | MDAlgorithms\Creation