+[NOR]
+Metropolis update.
+
+[R]
+Usual heatbath update
+phi'_x = sqrt(ln( 1/(1-r) )) * ( cos(theta) + i sin(theta) ) / sqrt(M) + V_x / M ,
+with r chosen randomly in [0,1] and theta chosen randomly in [0,2M_PI].
+
+[R+]
+R + overrelaxation.
+
+[1MR]
+Same as R, but with r = 1 - r_old instead of choosing r randomly in [0,1].
+
+[1MR+]
+1MR + overrelaxation.