Initial release

engine/plugins/solvers/euler.lua

@@ -0,0 +1,21 @@
+-- euler.lua: First-order Euler ODE solver
+-- Single evaluation, simplest possible solver.
+-- xt_next = xt - vt * (t_curr - t_prev)
+
+solver = {
+    name        = "euler",
+    display     = "Euler (ODE)",
+    description = "First-order Euler step (default)",
+    nfe         = 1,
+    order       = 1,
+    needs_model = false,
+    stateful    = false,
+    stochastic  = false,
+}
+
+function step(xt, vt, t_curr, t_prev, n)
+    local dt = t_curr - t_prev
+    for i = 0, n - 1 do
+        xt[i] = xt[i] - vt[i] * dt
+    end
+end