Tools
This page provides a brief description of several useful tool programs that are distributed
in the MFEM's miniapps/tools directory.
General Tools
Display Basis
The display-basis miniapp, found under miniapps/tools, visualizes various
types of finite element basis functions on a single mesh element in 1D, 2D,
and 3D.
The element type, basis type and order can be changed interactively. The mesh element is either the reference element, or a simple transformation of it.
Low-Order Refined Transfer
The lor-transfer miniapp, found under miniapps/tools demonstrates the
capability to generate a low-order refined mesh from a high-order mesh, and to
transfer solutions between these meshes.
Grid functions can be transferred between the coarse, high-order mesh and the low-order refined mesh using either $L^2$ projection or pointwise evaluation. These transfer operators can be designed to discretely conserve mass and to recover the original high-order solution when transferring a low-order grid function that was obtained by restricting a high-order grid function to the low-order refined space. The $L^2$ projection can also be weighted by a coefficient, in which case the transfer conserves the weighted mass — for example, transferring velocity while conserving density-weighted momentum.
DataCollection Tools
Convert DC
This tool, named convert-dc in the miniapps/tools subdirectory,
demonstrates how to convert between MFEM's different concrete
DataCollection options.
Currently supported data collection type options:
| Nickname | Full Class Name |
|---|---|
| visit | VisItDataCollection (default) |
| sidre or sidre_hdf5 | SidreDataCollection |
| json | ConduitDataCollection w/ protocol json |
| conduit_json | ConduitDataCollection w/ protocol conduit_json |
| conduit_bin | ConduitDataCollection w/ protocol conduit_bin |
| hdf5 | ConduitDataCollection w/ protocol hdf5 |
Load DC
The load-dc miniapp, found in the miniapps/tools subdirectory, loads and
visualizes (in GLVis) previously saved data using DataCollection sub-classes,
see e.g. Example 5/5p.
Currently, only the VisItDataCollection class is supported.
Compare DC
The compare-dc miniapp, found in the miniapps/tools subdirectory, loads two
sets of previously saved data using DataCollection sub-classes and computes the
$L^2$ norm of their difference. When a tolerance is provided with the -tol
option, the symmetric relative difference is compared against it and an error
is reported if the tolerance is exceeded.
Currently, only the VisItDataCollection class is supported.
Get Values
The get-values miniapp, found in miniapps/tools, loads previously saved
data using DataCollection sub-classes and outputs field values at a set of
points. Currently, only the VisItDataCollection class is supported.
# Number of fields
3
# Legend
# "Index" "Location":2 "pressure":1 "velocity":2
2 1 2
# Number of points
6
0 0.0 0.8 0.717336 -0.716172 -0.696674
1 0.2 0.8 0.876045 -0.875874 -0.852278
2 0.4 0.8 1.06999 -1.07106 -1.03923
3 0.6 0.8 1.30719 -1.30931 -1.26903
4 0.8 0.8 1.59678 -1.59601 -1.54949
5 1.0 0.8 1.94995 -1.94853 -1.89371
Point locations can be specified on the command line using -p or within a
data file whose name can be given with option -pf. The data file format is:
number_of_points space_dimension
x_0 y_0 ...
x_1 y_1 ...
etc.
By default all available fields are evaluated. The list of fields can be
reduced by specifying the desired field names with -fn. The -fn option
takes a space separated list of field names surrounded by quotes. Field
names containing spaces, such as "Field 1" and "Field 2", can be entered as:
get-values -fn "Field\ 1 Field\ 2"
By default the data is written to standard out. This can be overwritten
with the -o [filename] option.
The output format contains comments as well as sizing information to aid in subsequent processing. The bulk of the data consists of one line per point with a 0-based integer index followed by the point coordinates and then the field data. A legend, appearing before the bulk data, shows the order of the fields along with the number of values per field (for vector data).