RecordingDevice


Name:
RecordingDevice - Common properties of all recording devices.
Description:
 

Recording devices are used to measure properties of or signals emitted
by network nodes, e.g., using a multimeter, voltmeter or a spike detector.

Recording devices can collect data in memory, display it on the terminal
output or write it to file in any combination. The output format can be
controlled by device parameters as discussed below.

Recording devices can be subdivided into two groups: collectors and samplers.
- Collectors collect events sent to them; the spike detector is the
archetypical example. Nodes are connected to collectors and the collector
then collects all spikes emitted by the nodes connected to it and records
them.
- Samplers actively interrogate their targets at given time intervals
(default: 1ms), and record the data they obtain. This means that the sampler
must be connected to the node (not the node to the sampler), and that the
node must support the particular type of sampling; see device specific
documentation for details.

Recording devices share the start, stop, and origin parameters global to
devices. Start and stop have the following meaning for stimulating devices
(origin is just a global offset):
- Collectors collect all events with timestamps T that fulfill
start < T <= stop.
Note that events with timestamp T == start are NOT recorded.
- Sampling devices sample at times t = nh with
start < t <= stop
(t-start) mod interval == 0

Parameters:
 
The following parameters are shared with all devices:
/start - Activation time, relative to origin.
/stop - Inactivation time, relative to origin.
/origin - Reference time for start and stop.

The following parameter is only relevant for sampling devices:
/interval - Sampling interval in ms (default: 1ms).

The following parameters control where output is sent/data collected:
/record_to - An array containing any combination of /file, /memory, /screen,
indicating whether to write to file, record in memory or write
to the console window. An empty array turns all recording of
individual events off, only an event count is kept. You can also
pass strings (file), (memory), (screen), mainly for compatibility
with Python.

The name of the output file is
data_path/data_prefix(label|model_name)-gid-vp.file_extension

See /label and /file_extension for how to change the name.
/data_prefix is changed in the root node. If you change any part
of the name, an open file will be closed and a new file opened.

To close the file, pass a /record_to array without /file, or pass
/to_file false. If you later turn recording to file on again, the
file will be overwritten, unless you have changed data_prefix,
label, or file_extension.

/to_file - If true, turn on recording to file. Similar to /record_to
[/file], but does not affect settings for recording to memory and
screen.
/to_screen - If true, turn on recording to screen. Similar to /record_to
[/screen], but does not affect settings for recording to memory
and file.
/to_memory - If true, turn on recording to memory Similar to /record_to
[/memory], but does not affect settings for recording to file and
screen.

/filenames - Array containing the filenames where data is recorded to. This
array has one entry per local thread and is only available if
/to_file is set to true, or if /record_to contains /to_file.

/label - String specifying an arbitrary label for the device. It is used
instead of model_name in the output file name.
/file_extension - String specifying the file name extension, without leading
dot. The default depends on the specific device.
/close_after_simulate - Close output stream before Simulate returns. If set to
false, any output streams will remain open when
Simulate returns. (Default: false).
/flush_after_simulate - Flush output stream before Simulate returns. If set to
false, any output streams will be in an undefined
state when Simulate returns. (Default: true).
/flush_records - Flush output stream whenever new data has been written to the
stream. This may impede performance (Default: false).
/close_on_reset - Close output file stream upon ResetNetwork. Upon the next
call to Simulate, the file is reopened, overwriting its
contents. If set to false, the file will remain open after
ResetNetwork, so you can record continuously. NB:
the file is always closed upon ResetKernel. (Default: true).
/use_gid_in_filename - Determines if the GID is used in the file name of the
recording device. Setting this to false can lead to conflicting file names.

The following parameters control how output is formatted:
/withtime - boolean value which specifies whether the network time should
be recorded (default: true).
/withgid - boolean value which specifies whether the global id of the
observed node(s) should be recorded (default: false).
/withweight - boolean value which specifies whether the weight of the event
should be recorded (default: false).
/time_in_steps - boolean value which specifies whether to print time in steps,
i.e., multiples of the resolution, rather than in ms. If
combined with /precise_times, each time is printed as a pair
of an integer step number and a double offset < 0.
/precise_times - boolean value which specifies whether offsets describing the
precise timing of a spike within a time step should be taken
into account when computing the spike time. This is only
useful when recording from neurons that can emit spikes
off-grid (see module precise). Times are given in
milliseconds. If /time_in_steps is true, times are given as
steps and negative offset.
/scientific - if set to true, doubles are written in scientific format,
otherwise in fixed format; affects file output only, not
screen output (default: false)
/precision - number of digits to use in output of doubles to file
(default: 3)
/binary - if set to true, data is written in binary mode to files
instead of ASCII. This setting affects file output only, not
screen output (default: false)
/fbuffer_size - the size of the buffer to use for writing to files. Setting
this value to 0 will reduce buffering to a system-dependent
minimum. Set /flush_after_simulate to true to ensure that all
pending data is written to file before Simulate returns. A
value of -1 shows that the system default is in use. This
value can only be changed before Simulate is called.

Data recorded in memory is available through the following parameter:
/n_events - Number of events collected or sampled. n_events can be set to
0, but no other value. Setting n_events to 0 will delete all
spikes recorded in memory. n_events will count events even
when not recording to memory.
/events - Dictionary with elements /senders (sender GID, only if
/withgid or /withpath are true), /times (spike times in ms or
steps, depending on /time_in_steps; only if /withtime is
true) and /offsets (only if /time_in_steps, /precise_times
and /withtime are true). All data stored in memory is erased
when /n_events is set to 0.

Remarks:
 
- Recording devices can only reliably record data generated during the
previous min_delay interval. This means that in order to ensure consistent
results, you should always set a stop time for a recording device that is at
least one min_delay before the end of the simulation time.
- By default, devices record to memory. If you want to record to file, it may
be a good idea to turn off recording to memory, to avoid that you computer's
memory fills up with gigabytes of data:
<< /to_file true /to_memory false >>.
- Events are not necessarily recorded in chronological order.
- The device will not open an existing file, since that would erase the
existing data in the file. If you want existing files to be overwritten
automatically, you must set /overwrite_files in the root node.

SeeAlso: Source:
/home/nest/work/nest-2.14.0/nestkernel/recording_device.h