LHCbMath:

LHCbMath, Positive

• "improve" a bit the shape of "default" Positive polynomial (make it a bit more intuitive)
• extend the test to cover this case

this MR for 2018-patches and master branches

Kernel/LHCbMath/src/Bernstein1D.cpp

@@ -258,9 +258,9 @@ bool Gaudi::Math::Positive::updateBernstein ()
   //
   // get the parameters of "global" parabola
   //
-  const double a0     = m_sphere.x2 ( 0 ) ;
-  const double a1_    = m_sphere.x2 ( 1 ) ;
-  const double a2     = m_sphere.x2 ( 2 ) ;
+  const double a0     =     m_sphere.x2 ( 0 ) ;
+  const double a1_    = 2 * m_sphere.x2 ( 1 ) ; // NB: note factor 2 here! 
+  const double a2     =     m_sphere.x2 ( 2 ) ;
   //
   const double a1_min = - std::sqrt ( a0 * a2 ) ; //
   const double a1     = a1_min + a1_ ;            // positivity constraint