Add residual_order_condition

Author: YingboMa

Project.toml

@@ -12,6 +12,7 @@ Logging = "56ddb016-857b-54e1-b83d-db4d58db5568"
 NLsolve = "2774e3e8-f4cf-5e23-947b-6d7e65073b56"
 RecipesBase = "3cdcf5f2-1ef4-517c-9805-6587b60abb01"
 RecursiveArrayTools = "731186ca-8d62-57ce-b412-fbd966d074cd"
+RootedTrees = "47965b36-3f3e-11e9-0dcf-4570dfd42a8c"
 Statistics = "10745b16-79ce-11e8-11f9-7d13ad32a3b2"
 
 [compat]
@@ -22,6 +23,7 @@ DiffEqProblemLibrary = "4.5"
 NLsolve = "4.2"
 RecipesBase = "0.7, 0.8, 1.0"
 RecursiveArrayTools = "2"
+RootedTrees = "1"
 julia = "1"
 
 [extras]

src/DiffEqDevTools.jl

@@ -40,7 +40,7 @@ export test_convergence, analyticless_test_convergence, appxtrue!, appxtrue
 export get_sample_errors
 
 #Plot Functions
-export stability_region
+export stability_region, residual_order_condition
 
 #Tableaus
 export deduce_Butcher_tableau

src/tableau_info.jl

@@ -1,4 +1,4 @@
-using NLsolve, LinearAlgebra
+using NLsolve, LinearAlgebra, RootedTrees
 """
 `Base.length(tab::ODERKTableau)`
 
@@ -29,3 +29,16 @@ function stability_region(tab::ODERKTableau; initial_guess=-3.0)
   sol = nlsolve(residual!, [initial_guess])
   sol.zero[1]
 end
+
+function RootedTrees.residual_order_condition(tab::ODERKTableau, order::Int, reducer=nothing, mapper=x->x^2)
+  if reducer === nothing
+    resid = map(RootedTreeIterator(order)) do t
+      residual_order_condition(t, tab.A, tab.α, tab.c)
+    end
+  else
+    resid = mapreduce(reducer, RootedTreeIterator(order)) do t
+      mapper(residual_order_condition(t, tab.A, tab.α, tab.c))
+    end
+  end
+  return resid
+end