LArSoft

The first step is the redefinition of the content of recob::Track.
The design and implementation of it is staged:

1. the new data structures are plugged into LArSoft with an interface as backward-compatible as possible, to minimise the impact on current code
2. the code is transitioned into the new interface; utilities are provided for writing the new objects in a compliant way and for basic navigation
3. a complete navigation interface is provided

The delivery time of first stage is constrained by MicroBooNE production, whose official deadline is end of January 2017.

The material for stage 1 (see note 4) has been delivered in branches feature/cerati_TrackTrajectory (including lardataobj and others).

This is scheduled for merge into LArSoft v06_23_00 (which was basically delayed to merge it).

The new recob::Track class interface is as backward-compatible as possible to the old one.
Some data members are been left in there until there is agreement on how to life without them (issue #15453).

Interface change¶

Some data members underwent an interface change. These were the only cases where a change was unavoidable.

• DirectionAtPoint(), LocationAtPoint(), Vertex(), End(), VertexDirection(), EndDirection() return a TVector3 instead than a TVector3 const&
• CovarianceAtPoint(), VertexCovariance() and EndCovariance() return a TMatrixD instead of a TMatrixD const&

Typically this is a problem when storing the return into a reference variable, e.g.

TVector const& vertex = track.Vertex();

decltype(auto) vertex = track.Vertex();

Deprecated methods¶

A few methods have been formally deprecated. This means that every time you use one of them in your code, the compiler will give you a warning.
You can and should fix your code to avoid that. Please also report cases where LArSoft still uses them, in case we missed (m)any.

• Extent(std::vector<double>&, std::vector<double>&) const: use Extent() instead; it returns a pair of recob::Track::Point_t. If your use requires std::vector<double>, please contact us so that the downstream interface can be extended to support Point_t as well.
• NumberFitMomentum(): the new protocol requires the presence of as many momenta as there are points in a track trajectory, or none at all. Therefore, use NumberTrajectoryPoints() to know how many of both there are in the track. Another use in the code was to determine whether there was momentum information available in the track or not. In that case, the usual check if (track.NumberFitMomentum() > 0) should be replaced by if (track.HasMomentum()).

• TrajectoryAtPoint(size_t, TVector3&, TVector3&): the new method TrajectoryPoint(size_t) (no more At in the name!) returns a TrajectoryPoint_t object with copies of the direction and momentum. Note that this is different from before, where the returned vector was a direction rather than a momentum. Also, the results are not TVector3 any more, but rather Point_t and Vector_t.
• Direction(double*, double*) has gone through a treatment similar to Extent(TVector3&, TVector3&) (see above); the return type of the replacement, Direction(), is a pair of Vector_t.
• GlobalToLocalRotationAtPoint(size_t, TMatrixD&), LocalToGlobalRotationAtPoint(size_t, TMatrixD&) should be replaced by GlobalToLocalRotationAtPoint(size_t) and LocalToGlobalRotationAtPoint(size_t) respectively, which return a rotation matrix (Rotation_t) that can be used directly on Point_t and Vector_t objects.

These members have not formally deprecated yet, and the compiler will not issue any warning when used.

An example of dealing with the Extent() change and tips for upgrading TVector3 to GenVector vectors (used by the new recob::Track interface) can be found in the From ROOT vectors (TVector3) to ROOT GenVector wiki page.

as part of a discussion with Erica, Gianluca and Giuseppe, decided that to proceed on this will provide an interface for writing tracks and one for reading tracks that hides connections between tracks in other products.
Giuseppe will take care of the writing interface, Gianluca will take care of the reading interface.