Performance issues

[darrnshn]

• Malloc
  • mcmc::ChainArray::lastState (unnecessary copy on return) [ez fix]
  • mcmc::bouncyBounds (allocates a lot of matrices and vectors)
  • mcmc::ChainArray::append (copies the sample each time) [can we move the sample?]
  • mcmc::ChainArray::flushToDisk (copies last state and pushes to the back) [surely, we could implement as a deque that "clears" everything]
  • mcmc::Sampler::propose (copies proposal; converts to vector) [let requesters take views]
• Switch to spdlog
  • el::base::Writer::initialize
  • el::base::RegisteredLoggers::get
  • pthread mutex lock (logger needs to lock for server, but not necessarily for agent?)
• string copies/allocation/deallocation
  • Socket::send [send should have emplacement overloads,
    should take address by ref,
    but data by both ref and rvalue ref, initialize protocol objects from the internal socket buffer]
  • Socket::recv [recv should only ever allocate a buffer once (for the data),
    recv should return Message which is a view of the buffers,
    msg is only valid after recv,
    msg unserialisation should take views,
    to store stuff, copy from the view on demand]
  • onResult (clocks and message destructor) [emplacement send]
• Heartbeat clocks [can we avoid updating the HB every single time we recv a msg?]