How to speed up eis_prep using a DLM#

A key part of eis_prep is to remove cosmic rays, a step that requires median filtering of the data. The IDL routine that performs this step (fmedian.pro) is quite slow, but there is the option to speed it up by calling out to a C routine. To do this requires setting up a dynamically-loadable module (DLM).

If you are using a shared Solarsoft distribution, please ask your Solarsoft administrator to perform the described steps. If you have your own copy of Solarsoft (e.g., on a laptop), then you can perform the steps yourself. For a shared distribution the administrator should repeat the steps for each of the different computer architectures that access Solarsoft (e.g., Mac, Linux).

Environment variables#

First, go into IDL and do:

IDL> help,!VERSION,/str

in particular, note down the entries for the tags 'OS' and 'ARCH' (for a Mac these entries may be 'darwin' and 'x86_64').

In your .cshrc (or equivalent) file, set the following environment variables:

setenv SSW_COMPILE_TYPE <<OS>>
setenv SSW_BINARY_TYPE $SSW_COMPILE_TYPE.<<ARCH>>
setenv SSW_DLM_TOP $SSW/site/dlm
setenv IDL_DLM_PATH "<IDL_DEFAULT>:$SSW_DLM_TOP/$SSW_BINARY_TYPE"

where you should replace the values of <<OS>> and <<ARCH>> with the values you found from IDL.

Make sure that you source the .cshrc file before proceeding:

> source .cshrc

Create executable#

First create the directory in which the executable will go:

> mkdir -f $SSW_DLM_TOP/$SSW_BINARY_TYPE

Then go into the dlm directory in SSW:

> cd $SSW/gen/dlm

and type

> make rounds

Test#

Now go into IDL and do:

IDL> help,fmedian(fltarr(10,10),3,3)

You should see the message "% Loaded DLM: FMEDIAN" (note the DLM). If yes, then you now have the fmedian DLM working and you should find that eis_prep runs more quickly!