reset threads in semidiscretize

I added the option to reset the threads from Polyester.jl in semidiscretize.
However, I did not document it in the docstring since we have not documented
that we use Polyester.jl threads in general - and the resetting is specific
to Polyester.jl. I was not sure whether we still would like to keep the option
to change the threading backend any time - although I do not see a good reason
why we should do so.

Project.toml

@@ -65,7 +65,7 @@ MuladdMacro = "0.2.2"
 Octavian = "0.3.5"
 OffsetArrays = "1.3"
 P4est = "0.4"
-Polyester = "0.3.4, 0.5, 0.6, 0.7"
+Polyester = "0.7.5"
 PrecompileTools = "1.1"
 RecipesBase = "1.1"
 Reexport = "1.0"

src/Trixi.jl

@@ -51,7 +51,7 @@ using LoopVectorization: LoopVectorization, @turbo, indices
 using StaticArrayInterface: static_length # used by LoopVectorization
 using MuladdMacro: @muladd
 using Octavian: Octavian, matmul!
-using Polyester: @batch # You know, the cheapest threads you can find...
+using Polyester: Polyester, @batch # You know, the cheapest threads you can find...
 using OffsetArrays: OffsetArray, OffsetVector
 using P4est
 using Setfield: @set

src/semidiscretization/semidiscretization.jl

@@ -70,7 +70,15 @@ end
 Wrap the semidiscretization `semi` as an ODE problem in the time interval `tspan`
 that can be passed to `solve` from the [SciML ecosystem](https://diffeq.sciml.ai/latest/).
 """
-function semidiscretize(semi::AbstractSemidiscretization, tspan)
+function semidiscretize(semi::AbstractSemidiscretization, tspan;
+                        reset_threads = true)
+    # Optionally reset Polyester.jl threads. See
+    # https://github.com/trixi-framework/Trixi.jl/issues/1583
+    # https://github.com/JuliaSIMD/Polyester.jl/issues/30
+    if reset_threads
+        Polyester.reset_threads!()
+    end
+
     u0_ode = compute_coefficients(first(tspan), semi)
     # TODO: MPI, do we want to synchronize loading and print debug statements, e.g. using
     #       mpi_isparallel() && MPI.Barrier(mpi_comm())
@@ -88,7 +96,15 @@ that can be passed to `solve` from the [SciML ecosystem](https://diffeq.sciml.ai
 The initial condition etc. is taken from the `restart_file`.
 """
 function semidiscretize(semi::AbstractSemidiscretization, tspan,
-                        restart_file::AbstractString)
+                        restart_file::AbstractString;
+                        reset_threads = true)
+    # Optionally reset Polyester.jl threads. See
+    # https://github.com/trixi-framework/Trixi.jl/issues/1583
+    # https://github.com/JuliaSIMD/Polyester.jl/issues/30
+    if reset_threads
+        Polyester.reset_threads!()
+    end
+
     u0_ode = load_restart_file(semi, restart_file)
     # TODO: MPI, do we want to synchronize loading and print debug statements, e.g. using
     #       mpi_isparallel() && MPI.Barrier(mpi_comm())

src/semidiscretization/semidiscretization_hyperbolic_parabolic.jl

@@ -274,7 +274,15 @@ The parabolic right-hand side is the first function of the split ODE problem and
 will be used by default by the implicit part of IMEX methods from the
 SciML ecosystem.
 """
-function semidiscretize(semi::SemidiscretizationHyperbolicParabolic, tspan)
+function semidiscretize(semi::SemidiscretizationHyperbolicParabolic, tspan;
+                        reset_threads = true)
+    # Optionally reset Polyester.jl threads. See
+    # https://github.com/trixi-framework/Trixi.jl/issues/1583
+    # https://github.com/JuliaSIMD/Polyester.jl/issues/30
+    if reset_threads
+        Polyester.reset_threads!()
+    end
+
     u0_ode = compute_coefficients(first(tspan), semi)
     # TODO: MPI, do we want to synchronize loading and print debug statements, e.g. using
     #       mpi_isparallel() && MPI.Barrier(mpi_comm())