use stable implementation of QedQcd::toMz()

The new implementation is stable in the sense that it can be called
multiple times and the result stays the same.  Furthermore, it is
thread-safe.

src/lowe.cpp

@@ -342,41 +342,10 @@ double QedQcd::extractPoleMb(double alphasMb)
   return mbPole;
 }
 
-// Calculates the pole mass from the running mass, which should be defined at
-// mb
-void QedQcd::calcPoleMb()
-{
-  const double alphasMZ = displayAlpha(ALPHAS);
-  const double alphaMZ = displayAlpha(ALPHA);
-  const double saveMu = get_scale();
-
-  runGauge(get_scale(), displayMass(mBottom));
-  const double poleMb = extractPoleMb(displayAlpha(ALPHAS));
-  setPoleMb(poleMb);
-
-  // Reset to erase numerical integration errors.
-  setAlpha(ALPHAS, alphasMZ);
-  setAlpha(ALPHA, alphaMZ);
-  set_scale(saveMu);
-}
-
 // Takes QedQcd object created at MZ and spits it out at MZ
 void QedQcd::toMz()
 {
-  const double mt = input(MT_pole), as = a(ALPHAS - 1);
-  setMass(mTop, getRunMtFromMz(mt, as, displayPoleMZ()));
-  calcPoleMb();
-
-  const double tol = 1.0e-5;
-  const double alphasMZ = displayAlpha(ALPHAS);
-  const double alphaMZ = displayAlpha(ALPHA);
-  const double mz = displayPoleMZ();
-
-  runGauge(mz, 1.0);
-  run(1.0, mz, tol);
-  // Reset alphas to erase numerical integration errors.
-  setAlpha(ALPHAS, alphasMZ);
-  setAlpha(ALPHA, alphaMZ);
+   to(displayPoleMZ());
 }
 
 /**

src/lowe.h

@@ -104,9 +104,6 @@ class QedQcd: public flexiblesusy::Beta_function
 
   /// calculates pole bottom mass given alpha_s(Mb)^{MSbar} from running b mass
   double extractPoleMb(double asMb);
-  /// Calculates the pole mass from the running mass, which should be defined
-  /// at mb
-  void calcPoleMb();
 
 public:
   QedQcd();

test/test_QedQcd.cpp

@@ -29,5 +29,5 @@ BOOST_AUTO_TEST_CASE( test_QedQcd_toMz )
    q1.toMz();
    q2.toMz();
 
-   BOOST_CHECK(ToDoubleVector(q1.get()) == q2.display());
+   BOOST_CHECK_LT((q1.get() - ToEigenArray(q2.display())).abs().maxCoeff(), 2e-3);
 }