[Noise] Get rid of logVmin

dune/tectonic/frictionpotential.hh

@@ -37,7 +37,7 @@ class FrictionPotential : public FrictionPotentialWrapper {
     if (V <= Vmin)
       return 0.0;
 
-    return fd.a * (std::log(V) - logVmin);
+    return fd.a * (std::log(V / fd.V0) + logrest);
   }
 
   double differential(double V) const {
@@ -61,17 +61,15 @@ class FrictionPotential : public FrictionPotentialWrapper {
   }
 
   void updateLogState(double logState) {
-    double const tmp =
-        (fd.mu0 + fd.b * (logState + std::log(fd.V0 / fd.L))) / fd.a;
-    logVmin = std::log(fd.V0) - tmp;
-    Vmin = fd.V0 / std::exp(tmp);
+    logrest = (fd.mu0 + fd.b * (logState + std::log(fd.V0 / fd.L))) / fd.a;
+    Vmin = fd.V0 / std::exp(logrest);
   }
 
 private:
   FrictionData const fd;
   double const weight;
   double const normalStress;
-  double logVmin;
+  double logrest;
   double Vmin;
 };