Barzilei Borwein gradient descent: set correct state if gradient is zero after init
Barzilei Borwein gradient descent: set correct state if gradient is zero after init

MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3