Remove resume_from and default_chain_type

HISTORY.md

@@ -54,6 +54,11 @@ The separation of these functions was primarily implemented to avoid performing
 
 Previously `VarInfo` (or more correctly, the `Metadata` object within a `VarInfo`), had a flag called `"del"` for all variables. If it was set to `true` the variable was to be overwritten with a new value at the next evaluation. The new `InitContext` and related changes above make this flag unnecessary, and it has been removed.
 
+### Removal of `resume_from`
+
+The `resume_from=chn` keyword argument to `sample` has been removed; please use `initial_state=DynamicPPL.loadstate(chn)` instead.
+`loadstate` is exported from DynamicPPL.
+
 **Other changes**
 
 ### `setleafcontext(model, context)`

src/DynamicPPL.jl

@@ -130,6 +130,8 @@ export AbstractVarInfo,
     prefix,
     returned,
     to_submodel,
+    # Chain save/resume
+    loadstate,
     # Convenience macros
     @addlogprob!,
     value_iterator_from_chain,

src/sampler.jl

@@ -58,17 +58,15 @@ function AbstractMCMC.sample(
     model::Model,
     sampler::Sampler,
     N::Integer;
-    chain_type=default_chain_type(sampler),
-    resume_from=nothing,
     initial_params=init_strategy(sampler),
-    initial_state=loadstate(resume_from),
+    initial_state=nothing,
     kwargs...,
 )
     if hasproperty(kwargs, :initial_parameters)
         @warn "The `initial_parameters` keyword argument is not recognised; please use `initial_params` instead."
     end
     return AbstractMCMC.mcmcsample(
-        rng, model, sampler, N; chain_type, initial_params, initial_state, kwargs...
+        rng, model, sampler, N; initial_params, initial_state, kwargs...
     )
 end
 
@@ -79,26 +77,15 @@ function AbstractMCMC.sample(
     parallel::AbstractMCMC.AbstractMCMCEnsemble,
     N::Integer,
     nchains::Integer;
-    chain_type=default_chain_type(sampler),
     initial_params=fill(init_strategy(sampler), nchains),
-    resume_from=nothing,
-    initial_state=loadstate(resume_from),
+    initial_state=nothing,
     kwargs...,
 )
     if hasproperty(kwargs, :initial_parameters)
         @warn "The `initial_parameters` keyword argument is not recognised; please use `initial_params` instead."
     end
     return AbstractMCMC.mcmcsample(
-        rng,
-        model,
-        sampler,
-        parallel,
-        N,
-        nchains;
-        chain_type,
-        initial_params,
-        initial_state,
-        kwargs...,
+        rng, model, sampler, parallel, N, nchains; initial_params, initial_state, kwargs...
     )
 end
 
@@ -124,20 +111,12 @@ function AbstractMCMC.step(
 end
 
 """
-    loadstate(data)
+    loadstate(chain::AbstractChains)
 
-Load sampler state from `data`.
-
-By default, `data` is returned.
-"""
-loadstate(data) = data
-
-"""
-    default_chain_type(sampler)
-
-Default type of the chain of posterior samples from `sampler`.
+Load sampler state from an `AbstractChains` object. This function should be overloaded by a
+concrete Chains implementation.
 """
-default_chain_type(::Sampler) = Any
+function loadstate end
 
 """
     initialstep(rng, model, sampler, varinfo; kwargs...)

test/sampler.jl

@@ -12,7 +12,7 @@
         @test AbstractMCMC.step(Xoshiro(468), g(), spl) isa Any
     end
 
-    @testset "initial_state and resume_from kwargs" begin
+    @testset "initial_state" begin
         # Model is unused, but has to be a DynamicPPL.Model otherwise we won't hit our
         # overloaded method.
         @model f() = x ~ Normal()
@@ -52,26 +52,15 @@
             chn = sample(model, spl, N_iters; progress=false, chain_type=MCMCChains.Chains)
             initial_value = chn[:x][1]
             @test all(chn[:x] .== initial_value) # sanity check
-            # using `initial_state`
             chn2 = sample(
                 model,
                 spl,
                 N_iters;
                 progress=false,
-                initial_state=chn.info.samplerstate,
+                initial_state=DynamicPPL.loadstate(chn),
                 chain_type=MCMCChains.Chains,
             )
             @test all(chn2[:x] .== initial_value)
-            # using `resume_from`
-            chn3 = sample(
-                model,
-                spl,
-                N_iters;
-                progress=false,
-                resume_from=chn,
-                chain_type=MCMCChains.Chains,
-            )
-            @test all(chn3[:x] .== initial_value)
         end
 
         @testset "multiple-chain sampling" begin
@@ -86,30 +75,17 @@
             )
             initial_value = chn[:x][1, :]
             @test all(i -> chn[:x][i, :] == initial_value, 1:N_iters) # sanity check
-            # using `initial_state`
             chn2 = sample(
                 model,
                 spl,
                 MCMCThreads(),
                 N_iters,
                 N_chains;
                 progress=false,
-                initial_state=chn.info.samplerstate,
+                initial_state=DynamicPPL.loadstate(chn),
                 chain_type=MCMCChains.Chains,
             )
             @test all(i -> chn2[:x][i, :] == initial_value, 1:N_iters)
-            # using `resume_from`
-            chn3 = sample(
-                model,
-                spl,
-                MCMCThreads(),
-                N_iters,
-                N_chains;
-                progress=false,
-                resume_from=chn,
-                chain_type=MCMCChains.Chains,
-            )
-            @test all(i -> chn3[:x][i, :] == initial_value, 1:N_iters)
         end
     end