add jld2 checkpointing for version controll

src/IO/JLD2.jl

@@ -0,0 +1,54 @@
+"""
+    checkpointing_jld2(dst, stokes, thermal, η, particles, phases, time)
+
+Save necessary data in `dst` as and jld2 file to restart the model from the state at `time`.
+If run in parallel, the file will be named after the corresponidng rank e.g.`checkpoint_rank_0.jld2`
+and thus can be loaded by the processor while restarting the simulation.
+If you want to restart your simulation from the checkpoint you can use load() and specify the MPI rank
+by providing a dollar sign and the rank number.
+
+   # Example
+    ```julia
+    checkpointing_jld2(
+        "path/to/dst",
+        stokes,
+        thermal,
+        η,
+        particles,
+        pPhases,
+        t,
+    )
+
+    restart = load("path/to/dst/checkpoint_rank_(igg.me).jld2")"
+    stokes = restart["stokes"]
+    thermal = restart["thermal"]
+    η = restart["η"]
+    particles = restart["particles"]
+    pPhases = restart["phases"]
+    t = restart["time"]
+    ```
+"""
+function checkpointing_jld2(dst, stokes, thermal, η, particles, phases, time; igg=igg::IGG)
+    !isdir(dst) && mkpath(dst) # create folder in case it does not exist
+    fname = joinpath(dst, "checkpoint_rank_$(igg.me).jld2")
+    return jldsave(
+        fname;
+        stokes=_tocpu(stokes),
+        thermal=_tocpu(thermal),
+        η=_tocpu(η),
+        particles=_tocpu(particles),
+        phases=_tocpu(phases),
+        time,
+    )
+end
+
+function struct2cpu(a::T) where T<:Union{StokesArrays, SymmetricTensor, ThermalArrays, Velocity, Residual}
+    nfields = fieldcount(T)
+    cpu_fields = ntuple(Val(nfields)) do i
+        struct2cpu(getfield(a, i))
+    end
+    return T(cpu_fields...)
+end
+
+@inline struct2cpu(A::Array) = A
+@inline struct2cpu(A::AbstractArray) = Array(A)