docs: add postprocessing advice for mixed mode sparse Jacobians (#817)

Author: gdalle

DifferentiationInterface/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Feat
+
+- Backend switching for Mooncake ([#768])
+
 ## [0.7.1]
 
 ### Feat
@@ -51,4 +55,5 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 [#795]: https://github.com/JuliaDiff/DifferentiationInterface.jl/pull/795
 [#790]: https://github.com/JuliaDiff/DifferentiationInterface.jl/pull/790
 [#788]: https://github.com/JuliaDiff/DifferentiationInterface.jl/pull/788
-[#782]: https://github.com/JuliaDiff/DifferentiationInterface.jl/pull/782
+[#782]: https://github.com/JuliaDiff/DifferentiationInterface.jl/pull/782
+[#768]: https://github.com/JuliaDiff/DifferentiationInterface.jl/pull/768

DifferentiationInterface/docs/src/explanation/advanced.md

@@ -86,7 +86,16 @@ AutoSparse(
 )
 ```
 
-At the moment, mixed mode tends to work best when the [`GreedyColoringAlgorithm`](@extref SparseMatrixColorings.GreedyColoringAlgorithm) is provided with a [`RandomOrder`](@extref SparseMatrixColorings.RandomOrder) instead of the usual [`NaturalOrder`](@extref SparseMatrixColorings.NaturalOrder).
+At the moment, mixed mode tends to work best (output fewer colors) when the [`GreedyColoringAlgorithm`](@extref SparseMatrixColorings.GreedyColoringAlgorithm) is provided with a [`RandomOrder`](@extref SparseMatrixColorings.RandomOrder) instead of the usual [`NaturalOrder`](@extref SparseMatrixColorings.NaturalOrder), and when "post-processing" is activated after coloring.
+For full reproducibility, you should use a random number generator from [StableRNGs.jl](https://github.com/JuliaRandom/StableRNGs.jl).
+Thus, the right setup looks like:
+
+```julia
+using StableRNGs
+
+seed = 3
+coloring_algorithm = GreedyColoringAlgorithm(RandomOrder(StableRNG(seed), seed); postprocessing=true)
+```
 
 ## Batch mode