If you are running into issues with memory consumption or slow response
of the IDV, there are several things you can do.
The amount of memory used by the IDV will depend on the size of
the datasets you use and the types of displays. Datasets
rendered as 2D depictions (plan views - contours or color shaded
displays) use much less memory than 3D displays (isosurfaces,
cross sections). Large datasets (images, dense grids) will
use much more memory.
There are several features in the IDV that allow you to more efficiently
view large datasets:
Temporal/Spatial Subset of Data
Some data sources allow you to subset the data temporally and spatially.
You can set these properties for all fields in a dataset through the
Properties menu of the data source (double click on the
Data Source in the Field Selector) or you can set
these for individual field using the tabs in the lower right corner
of the Field Selector. For more information, see
the Data Source Properties
section of the IDV User's Guide.
Memory allocation
By default, the IDV startup script (runIDV) allocates 512 megabytes of
maximum memory for Java. This is usually the optimum amount for a Windows
system with 1 gigabyte of physical memory (RAM). Windows takes up half of
that anyway and once Windows has to start swapping, performance severely
degrades. On a Linux system, you can probably get away with 700m for
1 Gb of memory as it does a much better job of swapping. All this also
depends on what else you are running on the machine and how much memory
those applications use.
If your system has more than 1 Gb of memory, increasing the amount
available to the IDV can improve performance for displaying large
datasets. You can change the runIDV script to increase the amount
of memory. In that script, change the -Xmx512m to some higher number
(e.g. -Xmx1024m). The number is the number of bytes, the trailing m is
a multiplier (m=mega). Do not use the maximum amount of memory on your
machine as some is needed for the operating system itself. If the system
has to use swap memory, performance will degrade as well. For a system
with 2 Gb of physical memory, you can probably allocate 1.5 Gb to the IDV.
If you have less than 1 Gb of RAM, you should start the IDV with about
1/2 of the total memory (e.g., if your system has only 512 megabytes of
RAM, you should use -Xmx256m).
Data Caching
By default, the IDV caches the data used for a display in memory.
If a field is used more than once for several displays, caching
the data prevents an additional reading from of the data from
disk or a remote server. If you are only displaying/using a
field (i.e. not using it for multiple displays or calculations),
you can keep the IDV from caching it in memory. You can
turn off data caching by unchecking the Cache data in memory
checkbox on the Data & Formats tab of
the user preferences (accessible from the Edit->Preferences menu).
Maximum grid/image size
You can also set the maximum size of a grid or image that will be displayed.
This will allow you to download a large image or grid, but it will be
re-sampled before displaying if it is larger than the maximum size you
have asked for. You can set the maximum image/grid size under
the Data & Formats tab of
the user preferences (accessible from the Edit->Preferences menu).
Fast Rendering
By default, the IDV will try to adjust the data renderings to account
for projection seams. This is computationally intensive in some cases
and slows down the display of data. When you set your preference to
"Use Fast Rendering" (under the General tab of the user
preferences (Edit->Preferences menu)), the IDV will not try
to account for the projection seams. If you are displaying data in
its native projection, this will result in faster rendering of the
data depiction. However, if you have several displays of data, each
from a different data source and on a different projection, you may see
anomalies in the displays (spurious lines, portions of images). At that
point, you can turn off fast rendering for a particular display using the
Edit->Properties menu of the Display Control for that display,
or set your system preference back to not use fast rendering.
