[mlpack] GSoC 2018: Particle Swarm Optimization

[Chintan Soni]

Hello Marcus,

Just submitted an initial PR about half an hour ago.
There were some minor styling errors which were fixed quite easily,
but while looking for the index of the best particle using
arma::index_min(), the code works correctly on my machine, but the
Jenkins build fails.
The error message is:

/pso/pso_impl.hpp:99:30: error: ‘index_min’ is not a member of ‘arma’
   arma::uword bestParticle = arma::index_min(particleBestFitnesses);

I double checked if there were any similar errors on my machine and
there were none. Is there something I'm missing out?

Thanks in advance for the help.

Regards,
Chintan