How best to reuse factors (CalcFactor)

[Affie]

With reference to this issue: #467 (comment)

Is this the best way (wrap it in another CalcFactor):

cfZij = CalcFactor( cfo.factor.Zij.mechanics, cfo.metadata, 0, length(cfo._legacyMeas), cfo._legacyMeas, cfo._legacyParams)

https://github.com/JuliaRobotics/RoME.jl/blob/f41342dd89c47c1a5e6699990889a7ff609f20e6/src/factors/flux/MixtureFluxPose2Pose2.jl#L150

I think saving the CalcFactor object will be more efficient?
We can look at it as part of the CCW FMD CalcFactor cleanup.

We should also add it to documentation in Caeser

[Affie]

What about this pattern:

function (cf::CalcFactor{<:Pose2Pose2})(X, p, q)
  return Pose2Pose2(X, p, q)
end

function (cf::CalcFactor{<:ScatterAlignPose2})(X, p, q)
   return Pose2Pose2(X, p, q)
end


@inline function Pose2Pose2(X, p, q)
  q̂ = allocate(q) 
  M = getManifold(Pose2)
  ϵ0 = getPointIdentity(M)
  exp!(M, q̂, ϵ0, X)
  Manifolds.compose!(M, q̂, p, q̂)   
  Xc = vee(M, q, log!(M, q̂, q, q̂))
  return Xc
end

[dehann]

Oh that's cool, haven't seen that before!

[Affie]

I don't know if it's a good idea though. I edited the code block to remove () I left from copy-paste.
It's a little weird to have the same name as the constructor that isn't a constructor.

[Affie]

Maybe just:

@inline function calcPose2Pose2(X, p, q) ...

[dehann]

oh right, it's just the constructor handle. Do we need this for the AD stuff?