National Radio
Astronomy Observatory

8.1.1 Environment Variables

There are a number of environment variables that the ASAP tools (and thus the SDtasks) use to control their operation. They are located in .asaprc and are described in the ASAP User Guide. Within CASA, they are contained in the Python dictionary sd.rcParams and are accessible through its keys and values. For SDtask users, the most important parameter is verbose, which controls the display of detailed messages from the tools. By default,

produced by lots of messages. Also, the scantable.storage parameter controls whether scantable operations are done in memory or on disk. The default is

which is the best choice if there is enough memory compared with a size of data to be loaded. On the other hand,

forces the task to store datasets on disk, which might be necessary when they are large. See § 8.3.1 for more details on the ASAP environment variables.

Important Note:
User must use sd.rcParams[scantable.storage’]=’disk’ with care when you call any tool level functions since some functions may overwrite original data even if you set sd.rcParams[’insitu’]=False, which tells the system not to overwrite original data (in contrast, setting sd.rcParams[’insitu’] to True forces to overwrite original data). Relevant methods, which may overwrite original data in the above case, are as follows:

• sd.average_time
• sd.merge
• four operations (+, -, *, /) of sd.scantable instance with scalar or array
• sd.scantable.add
• sd.scantable.clip
• sd.scantable.flag
• sd.scantable.flag_nans
• sd.scantable.flag_row
• sd.scantable.scale
• sd.scantable.recalc_azel
• any setter functions of sd.scantable class (both set_xxx and _setxxx functions)

If you only use SDtasks, you don’t need to worry about that since SDtasks are designed to keep original data unchanged.

More information about CASA may be found at the CASA web page

Copyright © 2010 Associated Universities Inc., Washington, D.C.

This code is available under the terms of the GNU General Public Lincense