Pattern Analysis and Machine Intelligence (TPAMI), 33(9):1806-1819,
2011.
-It works with negative edge lengths and stops computing new path when
-it can not find one of negative total length, instead of fixing the
-total number of paths to a constant K.
+This implementation is not the reference implementation used for the
+experiments presented in this article.
* INSTALLATION
-This software should compile with any C++ compiler. Just execute
+This software should compile with any C++ compiler. Under a unix-like
+environment, just execute
make
./mtp_example
./mtp tracker.dat
-It will load the tracker.dat saved by the previous command, run the
-detection, save the detected trajectories in result.trj, and the
+It will load the file tracker.dat saved by the previous command, run
+the detection, save the detected trajectories in result.trj, and the
underlying graph with occupied edges in graph.dot.
-You can produce a pdf from the latter with the dot command from
-graphviz:
+If you do have the graphviz set of tools installed, you can produce a
+pdf from the latter with the dot command:
dot < graph.dot -T pdf -o graph.pdf
The two main classes are MTPGraph and MTPTracker.
-The MTPGraph class stores a directed acyclic graph (DAG), with a
-length for each edge -- which can be negative -- and can compute the
-family of paths in this graph that globally minimizes the sum of edge
-lengths.
+The MTPGraph class contains a directed acyclic graph (DAG), with a
+length for each edge -- which can be negative -- and has methods to
+compute the family of paths in this graph that globally minimizes the
+sum of edge lengths.
-This means that it will iteratively add paths as long as it can find
-some with negative length. If there are no such path, it will compute
-no path at all. Note that the procedure is similar to that of KSP, in
-the sense that the family it computes eventually is globally optimal,
-even if the computation is iterative.
+If there are no path of negative length, this optimal family will be
+empty, since the minimum total length you can achieve is zero. Note
+that the procedure is similar to that of KSP, in the sense that the
+family it computes eventually is globally optimal, even if the
+computation is iterative.
-The MTPTracker class allows
+The MTPTracker is defined by
- (1) to define a spatial topology composed of
+ (1) a spatial topology composed of
- a number of locations
- the exits (a Boolean flag for each location and time step)
- (2) to define a number of time steps
+ (2) a number of time steps
- (3) to set for every location and time a detection score, which
- should stand for log(P(Y = 1 | X)/P(Y = 0 | X)) where Y is for
- the location occupancy and X the available observations.
+ (3) a detection score for every location and time, which stands for
+ log(P(Y = 1 | X)/P(Y = 0 | X)) where Y is the said location
+ occupancy and X the available observations.
-From this setting, it computes the best set of disjoint trajectories
-consistent with the topology, which maximizes the overall detection
-score (i.e. the sum of the detection scores of the nodes visited by
-the trajectories)
+From this setting, MTPTracker has methods to compute the best set of
+disjoint trajectories consistent with the topology, which maximizes
+the overall detection score (i.e. the sum of the detection scores of
+the nodes visited by the trajectories). If no trajectory of total
+positive detection score exists, this optimal set of trajectories will
+be empty.
The MTPTracker is a wrapper around the MTPGraph class.
-From the defined the spatial topology and number of time steps, it
-builds a graph with one source, one sink, and two nodes per location
-and time. This structure ensures that the trajectories computed by the
+From the defined spatial topology and number of time steps, it builds
+a graph with one source, one sink, and two nodes per location and
+time. This structure ensures that the trajectories computed by the
MTPTracker will be node-disjoint, since the trajectories computed by
the MTPGraph are edge-disjoint.
The edges from the source or to the sink, or between these pairs of
nodes, are of length zero, and the edges between the two nodes of such
-a pair have lengths equal to the opposite of the corresponding
-detection scores.
+a pair have negative lengths, equal to the opposite of the
+corresponding detection scores.
The file mtp_example.cc gives a very simple usage example of the
MTPTracker class by setting the tracker parameters dynamically, and
The tracker data file for MTPTracker::read has the following format,
where L is the number of locations and T is the number of time steps:
----------------------------- snip snip -------------------------------
-int:L int:T
+ ---------------------------- snip snip -------------------------------
+ int:L int:T
-bool:allowed_motion_from_1_to_1 ... bool:allowed_motion_from_1_to_L
-...
-bool:allowed_motion_from_L_to_1 ... bool:allowed_motion_from_L_to_L
+ bool:allowed_motion_from_1_to_1 ... bool:allowed_motion_from_1_to_L
+ ...
+ bool:allowed_motion_from_L_to_1 ... bool:allowed_motion_from_L_to_L
-bool:entrance_1_1 ... bool:entrance_1_L
-...
-bool:entrance_T_1 ... bool:entrance_T_L
+ bool:entrance_1_1 ... bool:entrance_1_L
+ ...
+ bool:entrance_T_1 ... bool:entrance_T_L
-bool:exit_1_1 ... bool:exit_1_L
-...
-bool:exit_T_1 ... bool:exit_T_L
+ bool:exit_1_1 ... bool:exit_1_L
+ ...
+ bool:exit_T_1 ... bool:exit_T_L
-float:detection_score_1_1 ... float:detection_score_1_L
-...
-float:detection_score_T_1 ... float:detection_score_T_L
----------------------------- snip snip -------------------------------
+ float:detection_score_1_1 ... float:detection_score_1_L
+ ...
+ float:detection_score_T_1 ... float:detection_score_T_L
+ ---------------------------- snip snip -------------------------------
The method MTPTracker::write_trajectories writes first the number of
trajectories, followed by one line per trajectory with the following
structure
----------------------------- snip snip -------------------------------
-int:traj_number int:entrance_time int:duration float:score int:location_1 ... int:location_duration
----------------------------- snip snip -------------------------------
+ ---------------------------- snip snip -------------------------------
+ int:traj_number int:entrance_time int:duration float:score int:location_1 ... int:location_duration
+ ---------------------------- snip snip -------------------------------
--
François Fleuret
projects / mtp.git / blobdiff