- Prior to 48cb54d1, Ceres' fmin/fmax() for Jets followed the convention
of std::min/max(), and always returned the first argument on equality,
irrespective of whether this argument was natively a scalar or a Jet.
- After 48cb54d1, Ceres' fmin/fmax() instead returned the second
argument on equality, again irrespective of whether this argument was
natively a scalar or a Jet.
- Now on equality we average the arguments as Jets, which ensures that
a consistent answer is produced irrespective of the ordering or type
(Jet or scalar) of the input arguments. This also ensures that we
preserve a non-zero derivative where it exists, excluding the edge
case of two Jet inputs with equal but oppositely signed infinitesimal
components.
- We retain the behaviour introduced in 48cb54d1 whereby NaNs are
treated as missing values, following the convention of
std::fmin/fmax().
- Raised as issue #816.
Change-Id: I01217c0e32c1be83be440e4515b57c79dd290923
Alex Stewart
f11c256265