Infrastructure

Problems accessing data, or data seems to have disappeared

Two things to check:

1. Have you been given access to view the data?
2. Has the data been removed due to the data retention policy?

For the first, new users to an experiment need to ask the experiment POC to add them to the experiment. After this is done, you must log out and log back in for the change to take affect.

For the second, when analysis code that used to work stops working, check to see if the xtc is visible. For example, if you are analyzing run 68 of xpptut13, take a look in the xtc directory for that experiment, i.e:

ls /reg/d/psdm/xpp/xpptut13/xtc

If the directory is visible but run 68 is not there, it maybe that the data was removed due to the Data Retention Policy. The data is still available on disk and can be restored using the Web Portal of Experiments.

If the xtc directory is not visible, make sure you are running on a node that can see the data (i.e, you are on a psana node, rather than a psdev or pslogin node). If it is still not visible, email pcds-help@slac.stanford.edu.

How do I use the LCLS batch farm?

Follow the instructions here: Submitting Batch Jobs

How do I keep programs running if a ssh connection fails

See if you can use the LSF batch nodes for your work. If not, three unix programs to help with this are tmux, nohup and screen. None of these programs will preserve a graphical program, or a X11 connection, so run your programs in terminal mode.

tmux

For example, with tmux, if one does

ssh psexport
ssh psana
# suppose we have landed on psanacs040 and that there is a matlab license here
tmux
matlab --nosplash --nodesktop 

If you lose the connection to psanacs040, you can go back to that node and reattach:

ssh psexport
ssh psanacs040
tmux attach

You need to remember the node you ran tmux on. If you are running matlab, you can run the matlab license script with the --show-users parameter to see where you are running it:

/reg/common/package/scripts/matlic  --show-users

nohup

You could run a batch process with nohup (no hangup) as follows

    nohup myprogram

For example, suppose we want to run a Python script that prints to the screen and save its output (the below syntax is for the bash shell):

nohup python myscript.py > myoutput 2>&1 &

Here we are capturing the output of the program in myoutput, along with anything it writes to stderr (the 2>&1), then putting it in the background. The job will persist after you logout. You can take a look at the output in the file myoutput the next day. As with tmux you will need to remember the node you launched nohup on.

Why did my batch job failed? I'm getting 'command not found'

Before running your script, make sure you can run something, for instance do

  bsub -q psnehq pwd

(substitute the appropriate queue for psnehq). If you created a script and are running

  bsub -q psnehq myscript

Then it maybe that the current directory is not in your path, run

  bsub -q psnehq ./myscript

Check that myscript is executable by yourself, check that you have the correct #! line to start the script.

Psana

Topics specific to Psana

Where is my epics variable?

Make sure it is a epics variable - it may be a control monitor variable. An easy way to see what is in the file is to use psana modules that dump data.  For instance:

  psana -m psana_examples.DumpEpics exp=cxitut13:run=0022

will show what epics variables are defined. Likewise

  psana -m psana_examples.DumpControl exp=xpptut13:run=0179

will almost always show what control variables are defined. It defaults to use the standard Source "ProcInfo()" for control data. It is possible (though very unlikely) for control data to come from a different source. One can use the EventKeys module to see all Source's present, and then specify the source for  DumpControl through a config file.

How do I access data inside a Psana class?

Look for an example in the psana_examples package that dumps this class. There should be both a C++ and Python module that dumps data for the class.

How do I find out the experiment number (expNum) or experiment?

Psana stores both the experiment and expNum in the environment object - Env that Modules are passed, or that one obtains from the DataSource in interactive Psana. See Interactive Analysis document and the C++ reference for Psana::Env

Why isn't there anything in the Psana Event?

This may be due to a problem in the DAQ software that was used during the experiment. The DAQ software may have incorrectly been setting the L3 trim flag. This flag is supposed to be set for events that should not processed (perhaps they did not meet a scientific criteria involving beam energy). When the flag is set, there should be very little in the xtc datagram - save perhaps epics updates. Psana (as of release ana-0.10.2 from October 2013) will by default not deliver these events to the user. The bug is that the flag was set when there was valid data. To force psana to look inside datagram's where L3T was set, use the option l3t-accept-only. To use this option from the command line do:

psana -o psana.l3t-accept-only=0 ...

Or you can add the option to your psana configuration file (if you are using one):

[psana]
l3t-accept-only=0

It seems that for as much as 5% of the time, CsPad DataV2 is not in the Event

The only distinction between CsPad DataV1 and DataV2 is the sparsification of particular sections as given in the configuration object. That is DataV2 may be sparser. The actual hardware is kicking out DataV1 but the DAQ event builder is making a DataV2 when it can. Sometimes the DAQ sends the original DataV1 instead of the DataV2. This can be due to limited resources, in particular competition with resources required for compressing cspad in the xtc files. If you do not find a DataV2 in the Event, look for a DataV2

Hdf5

Topics specific to hdf5

Why is there both CsPad DataV2 and CsPad DataV1 in the translation?

The only distinction between CsPad DataV1 and DataV2 is the sparsification of particular sections as given in the configuration object. That is DataV2 may be sparser. The actual hardware is kicking out DataV1 but the DAQ event builder is making a DataV2 when it can. Sometimes the DAQ sends the original DataV1 instead of the DataV2. This can be due to limited resources, in particular competition with resources required for compressing cspad in the xtc files.

How do I write hdf5 files from C++ or Python

Python:

From Python we recommend h5py. For interactive Python, an example is found at Using h5py to Save Data.
For Python you can also use pytables. This is installed in the analysis release. Do

import tables

In your Python code.

C++

If developing a Psana module to process xtc, consider splitting your module into a C++ module which puts ndarrays in the event store, and a Python module which retrieves them and writes the hdf5 file using h5py.
You can also work with the C interface to hdf5.  hdf5 is installed as a package in the analysis release. From your C++ code, do

#include "hdf5/hdf5.h"

A tip for learning hdf5 is to run example programs from an 'app' subdirectory of your package. For example, if you create an analysis release and a package for yourself, create an app subdirectory to that package and put an example file there:

~/myrelease/mypackage/app/hdf5_example.c

Now run 'scons' from the ~/myrelease directory, and then run hdf5_example.

Psana Modules - Using the Translator:

The Psana ddl based Translator can be used to write ndarrays, strings and a few simple types that C++ modules register. These will be organized in the same groups that we use to translate xtc to hdf5. Datasets with event times will be written as well. To use this, create a psana config file that turns off the translation of all xtc types but allows translation of ndarrays and strings. An example cfg file is here: psana_translate_noxtc.cfg You would just change the modules and files parameters for psana and the output_file parameter to Translator.H5Output. Load modules before the translator that put ndarrays into the event store. The Translator will pick them up and write them to the hdf5 file

TimeTool

Here we cover topics specific to the offline TimeTool module. The TimeTool results can be obtained in one of two ways depending on the experimental setup. The first is through EPICs PV's that are calculated during data acquisition. The second is during offline analysis using the psana module TimeTool.Analyze. Documentation on the psana TimeTool modules can be found in the psana - Module Catalog.

SXR case study: reference/signal in different runs

Below we go over a script for generated offline TimeTool data for an sxr experiment. For this experiment, run 144 was done with the beam blocked, and run 150 with the beam on. The laser is always on in both runs.

This requires some configuration of the TimeTool. We run the TimeTool.Analyze module on run 144 - telling it that the beam is always off. Analayze builds up a reference. We further configure Analyze to save the reference. We also save a averaged background image for our own interactive plotting later.

We then run TimeTool.Analyze on run 150. We save the resulting timetool values to an hdf5 file using the psana xtc to hdf5 translator, see The XTC-to-HDF5 Translator for details.

Finally, to check the work, we process run 150 in index mode, see psana - Python Script Analysis Manual for details on indexing mode (random access) to psana events. We load the time tool values from the h5 file and plot them against the opal, after subtracting our background image.

Here are instructions for setting up to run on this sxr experiment. Users of other experiments will not be able to run on this data and will want to modify the scripts for their own experiments. These instructions will reference the following two files. First, the main driver script in the release directory can be found Here (filename ttanalyze.py).

Second, library code for a package in the release can be found Here (filename ttlib.py).

To get setup, after setting up the analysis software environment, do

newrel ana-current myrel
cd myrel
sit_setup
addpkg TimeTool 
newpkg mypkg
mkdir mypkg/src

now copy ttanalyze.py above to myrel/ttanalyze.py
now copy ttlib.py to myrel/mypkg/src/ttlib.py

scons
chmod u+x ttanalyze.py

Now run 
./ttanalyze.py     

this should produce the files

ttref_sxrd5814_r0144.txt       # reference that TimeTool.Analayze produced
ttref_sxrd5814_r0144.npy       # our own background reference for plotting
tt_sxrd5814_r0150.h5           # the h5 file with the timetool results for r150

This script builds a background from the first 300 events in run 144,
and processes the first 500 events in run 150.

A recursive listing of the h5 file should show, among other groups:

h5ls -r tt_sxrd5814_r0150.h5 

/Configure:0000/Run:0000/CalibCycle:0000/ndarray_float64_1/noSrc__TTANA:FLTPOS/data Dataset {500/Inf}
/Configure:0000/Run:0000/CalibCycle:0000/ndarray_float64_1/noSrc__TTANA:FLTPOS/time Dataset {500/Inf}

The data dataset is the TimeTool values for FLTPOS. 
The time dataset stores the event id's for the data - the seconds, nanoseconds and fiducials.

After running the script once, the second time the script is run, it will produce
interactive plots.