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==========================================
Real-time data processing with indexamajig
==========================================
Instead of reading from files, indexamajig can get its data over a ZeroMQ
socket. Use ``--zmq-input`` instead of ``--input`` or ``-i``. An error will
be generated if you use ``--zmq-input`` and ``--input`` or ``-i``
simultaneously.
Indexamajig can use either a SUB (subscriber) or a REQ (request) socket. The
SUB socket type can be used for receiving data from OnDA/OM via the same
mechanism that the OnDA/OM GUI uses. In this case, you will also need to
specify which message prefixes to subscribe to using ``--zmq-subscribe``::
indexamajig --zmq-input=tcp://127.0.0.1:5002 \
--zmq-subscribe=ondaframedata \
-o output.stream -g Eiger.geom ...
You can use ``--zmq-subscribe`` multiple times to subscribe to multiple message
prefixes.
Note that this mode of operation does not combine well with multi-threading
in indexamajig - all worker processes will receive the same data! For anything
more than "taking a peek" at the data, use the REQ socket instead by using
``--zmq-request`` instead of ``--zmq-subscribe``. The argument to this option
is the string which should be sent in the request message::
indexamajig --zmq-input=tcp://127.0.0.1:5002 \
--zmq-request=next \
-o output.stream -g Eiger.geom ...
Because they represent completely different modes of operation, the two options
``--zmq-request`` and ``--zmq-subscribe`` are mutually exclusive.
In both cases, the option ``--no-image-data`` will be honoured, if given. This
makes it possible to quickly check streaming data for "indexability". You will
be able to do almost all of the usual downstream analysis operations on the
resulting stream, except that attempting to merge it using partialator or
process_hkl will result in zeroes everywhere.
Data format
===========
In this version, CrystFEL makes the following assumptions about the data
received via ZeroMQ:
* The data is serialised using MessagePack
* The data consists of either a single MsgPack 'map' object, or an array of
maps.
If there are multiple map objects in the array, only the first one will be
used. The others will be ignored.
* The image data is given as a two-dimensional array (i.e. no 3D arrays with
'panel number' as one of the dimensions).
* The image data itself is given as a MsgPack 'map' object representing a
serialised NumPy array. That is, it should contain ``type``, ``data`` and
``shape`` keys.
* The data ``type`` field should contain either ``<i4`` (if the data is in
little-endian 32-bit signed integer format) or ``<f4`` for 32-bit (IEEE754
single precision) floating-point.
* The data ``shape`` field should be a 1D array of two values. The first
element is the slow-scan size, the second is that fast-scan size.
* The data array within the NumPy map should be in a binary object called
``data``.
Note that *all* of the above assumptions are 'open for negotiation' and will be
relaxed in future CrystFEL versions, as new online data formats arise. Anyone
interested in streaming CBF files over ZeroMQ?
You can specify which map objects to look at in the geometry file. The
following example will get the incident photon energy (in eV) and detector
distance (in mm) by looking up the ``beam_energy`` and ``detector_distance``
keys, respectively, in the MsgPack map object. It will then look up
``detector_data`` to find the image data itself. See the next section for an
explanation of ``peak_list``::
photon_energy = beam_energy eV
adu_per_photon = 1
clen = detector_distance mm
res = 5814.0
peak_list = peak_list
thepanel/data = detector_data
thepanel/min_fs = 0
thepanel/max_fs = 2067
thepanel/min_ss = 0
thepanel/max_ss = 2161
thepanel/corner_x = -1034
thepanel/corner_y = -1081
thepanel/fs = x
thepanel/ss = y
Peak lists
==========
You can use all of the usual peak search methods for streaming data.
In addition, you can use ``--peaks=msgpack`` to get the peak locations from
the MsgPack data. In this case, the ``peak_list`` directive in the geometry
file specifies the key for the peak information in the MsgPack map object.
The peak information itself is expected to be a map object with three keys:
``fs``, ``ss`` and ``intensity``. Each of these keys should correspond to an
array containing (respectively) the fast scan and slow scan coordinates of each
peak, and their intensities. Obviously, the three arrays must have equal sizes.
Note that there is no way, in this structure, to communicate which detector
panel contains a peak, in the case where different detector panels cover the
same pixel ranges (in this case, the pixel data would from multiple data
blocks). In practice, this means that the ``data`` directives for all panels
need to be the same when using ``--peaks=msgpack``.
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