Fix RuinaFunction::evaluate()

dune/tectonic/nicefunction.hh

@@ -58,7 +58,7 @@ class RuinaFunction : public NiceFunction {
   void virtual evaluate(double const &x, double &y) const {
     double const arg = std::max(eta * x / h, rho);
     double const r = arg * (a * (std::log(arg) - 1) + mu + compound_state);
-    y = 1 / eta * normalStress * r + a * rho + mu + compound_state;
+    y = 1 / eta * normalStress * (r + a * rho + mu + compound_state);
     y *= coefficient;
     y *= h;
   }