add modifications

Shreyas-Ekanathan · Apr 16, 2024 · 3d2c40d · 3d2c40d
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Showing 3 changed files with 13 additions and 5 deletions.
diff --git a/src/algorithms.jl b/src/algorithms.jl
@@ -1211,6 +1211,8 @@ pages={113753}
 """
 struct ERKN7 <: OrdinaryDiffEqAdaptivePartitionedAlgorithm end
 
+struct RKN4 <: OrdinaryDiffEqAlgorithm end
+
 ################################################################################
 
 # Adams Bashforth and Adams moulton methods

diff --git a/src/perform_step/rkn_perform_step.jl b/src/perform_step/rkn_perform_step.jl
@@ -12,7 +12,7 @@ const NystromCCDefaultInitialization = Union{Nystrom4ConstantCache, FineRKN4Cons
     DPRKN4ConstantCache, DPRKN5ConstantCache,
     DPRKN6FMConstantCache, DPRKN8ConstantCache,
     DPRKN12ConstantCache, ERKN4ConstantCache,
-    ERKN5ConstantCache, ERKN7ConstantCache}
+    ERKN5ConstantCache, ERKN7ConstantCache, RKN4ConstantCache}
 
 function initialize!(integrator, cache::NystromCCDefaultInitialization)
     integrator.kshortsize = 2
@@ -1824,7 +1824,7 @@ function initialize!(integrator, cache::RKN4Cache)
     @unpack fsalfirst, k = cache
     duprev, uprev = integrator.uprev.x
     integrator.fsalfirst = fsalfirst
-    integrator.fsallast = cache.k₃
+    integrator.fsallast = k
     integrator.kshortsize = 2
     resize!(integrator.k, integrator.kshortsize)
     integrator.k[1] = integrator.fsalfirst
@@ -1868,15 +1868,18 @@ end
     integrator.u = ArrayPartition((du, u))
     integrator.fsallast = ArrayPartition((f.f1(du, u, p, t + dt), f.f2(du, u, p, t + dt)))
     integrator.stats.nf += 3
-    integrator.stats.nf2 += 1
+    integrator.stats.nf2 += 1    
     integrator.k[1] = integrator.fsalfirst
     integrator.k[2] = integrator.fsallast
 end
 
 @muladd function perform_step!(integrator, cache::RKN4Cache, repeat_step = false)
     @unpack t, dt, f, p = integrator
     duprev, uprev = integrator.uprev.x
-
+
+    @unpack tmp, fsalfirst, k₂, k₃, k = cache
+    kdu, ku = integrator.cache.tmp.x[1], integrator.cache.tmp.x[2]
+
     #define dt values
     halfdt = dt/2
     dtsq = dt^2
@@ -1903,6 +1906,9 @@ end
     u = uprev + sixthdtsq* (1*k₁ + 2*k₂ + 0*k₃) + dt * duprev
     du = duprev + sixthdt * (1*k₁ + 4*k₂ + 1*k₃)
 
+    f.f1(k.x[1], du, u, p, t + dt)
+    f.f2(k.x[2], du, u, p, t + dt)
+
     integrator.stats.nf += 3
     integrator.stats.nf2 += 1
 end
diff --git a/test/algconvergence/partitioned_methods_tests.jl b/test/algconvergence/partitioned_methods_tests.jl
@@ -110,7 +110,7 @@ sim = test_convergence(dts, prob, KahanLi8(), dense_errors = true)
 @test sim.𝒪est[:L2]≈4 rtol=1e-1
 
 sol = solve(prob, Nystrom4(), dt = 1 / 1000)
-RKN
+
 # Nyström method
 dts = 1 .// 2 .^ (9:-1:6)
 sim = test_convergence(dts, prob, OrdinaryDiffEq.RKN4(), dense_errors = true)