Daniel Sigg, May 2001
The LIGO Data Access Tool (Lidax) is a graphical user interface to retrieve data from the Laser Interferometer Gravitational-wave Observatory. Start Lidax by typing:
lidaxThis will bring up the following window:
The source area lets the user select the data server, the name of the data set, the channels of interest and the measurement time. If more than one server is selected, the data streams are merged as they are read. After selecting one or multiple data servers the user is presented with a list of available data set names in the UDN (Universal Data set Name) selection box. Selecting a UDN enables the channel selection window and the time selection window which should present a list of channels and measurement intervals, respectively.
Server Selection
Lidax currently supports the following data servers and data sources:
UDN Selection
A few examples of valid data set names (see Understanding UDNs for more details):
Channel Selection
The wildcard selection accepts * (star), ? (question mark) and [] (square brackets) and it supports the same matching as the unix command line (see fnmatch).
Time Selection
The client area lets the user select the data destination, the name of the data set, the channels of interest and the frame format. If more than one destination is selected, the data stream is split as it is written. After selecting one or multiple data sinks the user is presented with a list of available destinations in the UDN selection box. At this point it is also possible to specify a destination channel selection which has to be a subset of the combined list of source channels. Being able to set a channel list separately for each client makes it possible to split a frame stream into multiple data subsets concurrently. The user should also select an output frame format.
Client Selection
The output selection is limited to:
UDN Selection
Selecting a data set name is essentially the same as for a server. For more details about UDNs see the next section.
Channel Selection
This is identical to the source channel selection.
Format Selection
The frame file format is defined by the length of each frame in seconds, the number of frames per file and the compression method.
A data retrieveal or converting process may take a long time and being
able to monitor the progress can be convenient. A user has the choice between
several different reporting options:
The settings of the Lidax program can saved to file in the LIGO lightweight data format (XML). Saved settings can be restored from file as well.
This option is useful if the data is directly fed into one ore multiple DMT monitor processes. To make it work at least on of the destinations must be a shared memory partition. Monitors are typically started before the data retrieval process begins and the name of the shared memory partition is passed as a command line argument (denoted by "$part").
When the run button is pressed, the program forks in the background and starts the data retrieval and conversion process. It is not necessary to keep the terminal open.
A detailed description of UDNs can be found in T010062.
The following environmental variables can be set:
Examples:
setenv LIGOSMPART LHO_Online
setenv LIGOSMPARTS offline_1:offline_2
setenv NDSSERVER red.ligo-wa.caltech.edu,london.ligo-la.caltech.edu
setenv UDNFILE $HOME/file1.udn:$HOME/file2.udn
Example $HOME/file1.udn:
# E2 data on fortress
dir:///export/raid3/E2/00-11-08_19:59:35.@
dir:///export/raid2/E2/00-11-09_09:17:47.@
dir:///export/raid2/E2/00-11-12_17:10:19.@
dir:///export/raid2/E2/00-11-14_00:25:08.@
To accelerate disk access and make it more convenient for repeated tasks one can generate a UDN list and an associated channel list. These two lists can then be read by LiDaX/DTT without accessing the files first. For example:
udnls "/samraw/S3/L0/LHO/H-R-75*/*.gwf" > mylist.udnwill create a UDN list in mylist.udn and a channel list in mylist.chn. Pointing DTT to the frames directly would take a very very long time to load. The UDN file will look like this (where the c-option is used to denote how many files are continuously added to the series):
finfo -ce "/samraw/S3/L0/LHO/H-R-7555/H-R-755500000-16.gwf" > mylist.chn
file:///samraw/S3/L0/LHO/H-R-7511/H-R-751117376-16.gwf -c 36The channel file will look like this:
file:///samraw/S3/L0/LHO/H-R-7511/H-R-751119776-16.gwf -c 122
file:///samraw/S3/L0/LHO/H-R-7511/H-R-751122560-16.gwf -c 189
file:///samraw/S3/L0/LHO/H-R-7511/H-R-751198368-16.gwf -c 62
file:///samraw/S3/L0/LHO/H-R-7512/H-R-751203392-16.gwf -c 19
file:///samraw/S3/L0/LHO/H-R-7512/H-R-751210592-16.gwf -c 63
...
H1:SUS-MC1_URPOS_GAIN 16If you these are raw frames, DTT will spend most time building up the channel selection lists. You can further accelerate this by only listing the channels that are actually use. In most circumstances you can get rid of the slow channels. So,
H1:IOO-MC_F 16384
H2:LSC-ASPD1_TempMon 16
H1:SUS-SM_SPDMon 16
H2:SUS-RM_ULCOIL_INMON 16
H1:IOO-MC_I 16384
H1:SUS-SM_ASCPIT_GAIN 16
finfo -ce "/samraw/S3/L0/LHO/H-R-7555/H-R-755500000-16.gwf" | awk '$2>16' > mylist.chnmay be a faster option in most cases.
The Lidax program has the following usage format:
usage: lidax [-p] [-o 'dir' [-f 'format']]
lidax -h
lidax -H 'env'
-p : don't fork (useful for pipe)
-o 'dir' : output is written into specified directory
-f 'format' : output frame format
-h : this help
-H 'env' : help for an environment variable