From 366c030942141c0148b82ea21a6f84aa0abe5c36 Mon Sep 17 00:00:00 2001
From: Magnus Ulimoen <flymagnus@gmail.com>
Date: Mon, 4 May 2020 17:59:49 +0200
Subject: [PATCH] restrict c_max when using h2 operators

---
 multigrid/src/main.rs | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/multigrid/src/main.rs b/multigrid/src/main.rs
index b5f01aa..80cff29 100644
--- a/multigrid/src/main.rs
+++ b/multigrid/src/main.rs
@@ -132,7 +132,16 @@ impl System {
 
     /// Suggested maximum dt for this problem
     fn max_dt(&self) -> Float {
-        let c_max = 1.0;
+        let c_max = if self.operators.iter().any(|op| {
+            op.as_ref().either(
+                |op| op.is_h2xi() || op.is_h2eta(),
+                |op| op.is_h2xi() || op.is_h2eta(),
+            )
+        }) {
+            0.5
+        } else {
+            1.0
+        };
         let mut max_dt: Float = Float::INFINITY;
 
         for (field, metrics) in self.fnow.iter().zip(self.metrics.iter()) {