added docs for SLSDETNAME

docs/CMakeLists.txt

@@ -42,6 +42,7 @@ set(SPHINX_SOURCE_FILES
   src/pyexamples.rst
   src/pyPatternGenerator.rst
   src/servers.rst
+  src/multidet.rst
   src/receiver_api.rst
   src/result.rst
   src/type_traits.rst

docs/src/index.rst

@@ -28,6 +28,12 @@ Welcome to slsDetectorPackage's documentation!
     receiver_api
     examples
 
+.. toctree::
+    :caption: how to
+    :maxdepth: 2
+
+    multidet
+
 .. toctree::
     :caption: Python API
     :maxdepth: 2

docs/src/multidet.rst

@@ -0,0 +1,181 @@
+Using multiple detectors
+==========================
+
+The slsDetectorPackage supports using several detectors on the same computer.
+This can either be two users, that needs to use the same computer without interfering
+with each other, or the same user that wants to use multiple detectors at the same time.
+The detectors in turn can consist of multiple modules.
+
+In order to do this we have two tools to our disposal:
+
+#. Detector index 
+#. The SLSDETNAME environment variable
+
+They can be used together or separately depending on the use case.
+
+Detector index
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+When configuring a detector you can specify a detector index. The default is 0. 
+
+**Command line**
+
+.. code-block:: bash
+
+    # Configure detector with index 0
+    $ sls_detector_put hostname my-det
+    
+    # Set number of frames for detector 0 to 19
+    $ sls_detector_put frames 10
+
+
+    # Configure detector with index 1 (notice the 1- before hostname)
+    $ sls_detector_put 1-hostname my-det2
+    
+
+    # Further configuration
+    ...
+
+    # Set number of frames for detector 1 to 19
+    $ sls_detector_put 1-frames 19
+
+    # Note that if we call sls_detector_get without specifying the index,
+    # it will return the configuration of detector 0
+    $ sls_detector_get frames
+    10
+
+**Python**
+
+The main difference between the command line and the Python API is that you set the index
+when you create the detector object and you don't have to repeat it for every call.
+
+The C++ API works int the same way. 
+
+.. code-block:: python
+
+    from slsdet import Detector
+    
+    # Configure detector with index 0
+    d = Detector()
+
+    # If the detector has already been configured and has a shared memory
+    # segment, you can omit setting the hostname again
+    d.hostname = 'my-det'
+
+    #Further configuration
+    ...
+
+    # Configure a second detector with index 1
+    d2 = Detector(1)
+    d2.hostname = 'my-det2'
+   
+    d.frames = 10
+    d2.frames = 19
+ 
+
+$SLSDETNAME
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+To avoid interfering with other users on shared PCs it is best to always set the SLSDETNAME environmental variable.
+Imagining a fictive user: Anna, we can set SLSDETNAME from the shell before configuring the detector:
+
+**Command line**
+
+.. code-block:: bash
+
+    # Set the SLSDETNAME variable
+    $ export SLSDETNAME=Anna
+
+    # You can check that it is set
+    $ echo $SLSDETNAME
+    Anna
+
+    # Now configures a detector with index 0 and prefixed with the name Anna
+    # /dev/shm/slsDetectorPackage_detector_0_Anna
+    $ sls_detector_put hostname my-det
+
+
+.. tip ::
+
+    Set SLSDETNAME in your .bashrc in order to not forget it when opening a new terminal.
+
+
+**Python**
+
+With python the best way is to set the SLSDETNAME from the command line before starting the python interpreter.
+
+Bash:
+
+.. code-block:: bash
+
+    $ export SLSDETNAME=Anna
+
+Python:
+
+.. code-block:: python
+
+    from slsdet import Detector
+    
+    # Now configures a detector with index 0 and prefixed with the name Anna
+    # /dev/shm/slsDetectorPackage_detector_0_Anna
+    d = Detector()
+    d.hostname = 'my-det'
+
+You can also set SLSDETNAME from within the Python interpreter, but you have to be aware that it will only
+affect the current process and not the whole shell session.
+
+.. code-block:: python
+
+    import os
+    os.environ['SLSDETNAME'] = 'Anna'
+
+    # You can check that it is set
+    print(os.environ['SLSDETNAME'])  # Output: Anna
+
+    #Now SLSDETNAME is set to Anna but as soon as you exit the python interpreter
+    # it will not be set anymore
+
+.. note ::
+
+    Python has two ways of reading environment variables: `**os.environ**` as shown above which throws a
+    KeyError if the variable is not set and `os.getenv('SLSDETNAME')` which returns None if the variable is not set.
+
+    For more details see the official python documentation on: https://docs.python.org/3/library/os.html#os.environ
+
+
+Checking for other detectors
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+If using shared accounts on a shared computer (which you anyway should not do), it is good practice to check
+if there are other detectors configured by other users before configuring your own detector.
+
+You can do this by listing the files in the shared memory directory `/dev/shm/` that start with `sls`. In this
+example we can see that two single module detectors are configured one with index 0 and one with index 1.
+SLSDETNAME is set to `Anna` so it makes sense to assume that she is the user that configured these detectors.
+
+
+.. code-block :: bash
+
+    # List the files in /dev/shm that starts with sls
+    $ ls /dev/shm/sls*
+    /dev/shm/slsDetectorPackage_detector_0_Anna
+    /dev/shm/slsDetectorPackage_detector_0_module_0_Anna
+    /dev/shm/slsDetectorPackage_detector_1_Anna
+    /dev/shm/slsDetectorPackage_detector_1_module_0_Anna
+
+
+Other considerations
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The shared memory is not the only way to interfere with other users. You also need to make sure that you are not
+using the same:
+
+* rx_tcpport
+* udp_dstport
+* rx_zmqport
+* zmqport
+
+.. attention ::
+
+    The computer that you are using need to have enough resources to run multiple detectors at the same time.
+    This includes CPU and network bandwidth. Please coordinate with the other users!