mamba.jl: proof of per-chain tune reset

gistfile1.txt

After applying
``` diff
diff --git a/src/model/mcmc.jl b/src/model/mcmc.jl
index 8dc127c..30e3e61 100644
--- a/src/model/mcmc.jl
+++ b/src/model/mcmc.jl
@@ -61,9 +61,12 @@ end
 function mcmc_worker!(args::Vector)
   m, state, window, burnin, thin, meter = args

+  @show pointer_from_objref(m)
   m.iter = first(window) - 1
   relist!(m, state.value)
   settune!(m, state.tune)
+  @show pointer_from_objref(m.samplers[1].tune)
+  @show m.samplers[1].tune

   pnames = names(m, true)
   sim = Chains(last(window), length(pnames), start=burnin + thin, thin=thin,
diff --git a/src/samplers/sampler.jl b/src/samplers/sampler.jl
index 4032b7b..70aa579 100644
--- a/src/samplers/sampler.jl
+++ b/src/samplers/sampler.jl
@@ -37,6 +37,7 @@ function SamplerVariate{T<:SamplerTune, U<:Real}(x::AbstractVector{U},
                                                  s::Sampler{T},
                                                  pargs...; kargs...)
   if any(map(f -> !isdefined(s.tune, f), fieldnames(s.tune)))
+    info("resetting sampler ", typeof(s))
     v = SamplerVariate{T}(x, pargs...; kargs...)
     s.tune = v.tune
   else
```

running the seeds example 
``` julia
> julia -q doc/examples/seeds.jl             ~/.julia/v0.4/Mamba
MCMC Simulation of 12500 Iterations x 2 Chains...

pointer_from_objref(m) = Ptr{Void} @0x00007f7bf434a690
pointer_from_objref(m.samplers[1].tune) = Ptr{Void} @0x00007f7bf5ec7170
m.samplers[1].tune = Mamba.AMMTune(#undef,true,2.812953e-318,1,#undef,#undef,6.92576150559095e-310,#undef,#undef)
INFO: resetting sampler Mamba.Sampler{Mamba.AMMTune}
INFO: resetting sampler Mamba.Sampler{Mamba.AMWGTune}
INFO: resetting sampler Mamba.Sampler{Mamba.AMWGTune}
Chain 1:   0% [1:56:07 of 1:56:13 remaining]
Chain 1:  10% [0:01:22 of 0:01:31 remaining]
...

pointer_from_objref(m) = Ptr{Void} @0x00007f7bf434a690
pointer_from_objref(m.samplers[1].tune) = Ptr{Void} @0x00007f7bf5eb3b70
m.samplers[1].tune = Mamba.AMMTune(#undef,true,2.812953e-318,1,#undef,#undef,6.92576150559095e-310,#undef,#undef)
INFO: resetting sampler Mamba.Sampler{Mamba.AMMTune}
INFO: resetting sampler Mamba.Sampler{Mamba.AMWGTune}
INFO: resetting sampler Mamba.Sampler{Mamba.AMWGTune}
Chain 2:   0% [0:00:33 of 0:00:33 remaining]
Chain 2:  10% [0:00:31 of 0:00:35 remaining]
...

> julia -q -p2 doc/examples/seeds.jl         ~/.julia/v0.4/Mamba
MCMC Simulation of 12500 Iterations x 2 Chains...

        From worker 3:  pointer_from_objref(m) = Ptr{Void} @0x00007fc3e80d2b90
        From worker 2:  pointer_from_objref(m) = Ptr{Void} @0x00007f8e7eda0010
        From worker 3:  pointer_from_objref(m.samplers[1].tune) = Ptr{Void} @0x00007fc3ea7fd0a0
        From worker 3:  m.samplers[1].tune = Mamba.AMMTune(#undef,true,2.812953e-318,2,#undef,#undef,6.92780252952843e-310,#undef,#undef)
        From worker 2:  pointer_from_objref(m.samplers[1].tune) = Ptr{Void} @0x00007f8e819fe5e0
        From worker 2:  m.samplers[1].tune = Mamba.AMMTune(#undef,true,2.812953e-318,2,#undef,#undef,6.92780252952843e-310,#undef,#undef)
INFO: resetting sampler Mamba.Sampler{Mamba.AMMTune}
INFO: resetting sampler Mamba.Sampler{Mamba.AMMTune}
INFO: resetting sampler Mamba.Sampler{Mamba.AMWGTune}
INFO: resetting sampler Mamba.Sampler{Mamba.AMWGTune}
INFO: resetting sampler Mamba.Sampler{Mamba.AMWGTune}
INFO: resetting sampler Mamba.Sampler{Mamba.AMWGTune}
        From worker 3:  Chain 2:   0% [2:01:49 of 2:01:55 remaining]
        From worker 2:  Chain 1:   0% [2:02:33 of 2:02:39 remaining]
        From worker 3:  Chain 2:  10% [0:01:23 of 0:01:32 remaining]
        From worker 2:  Chain 1:  10% [0:01:22 of 0:01:31 remaining]
```

As one can see, each sampler gets reseted once per chain.