Add 2D field plotter and parameter reduction operators

1. Add a 2D field plotter operator (hysop/operator/plotters.py)
2. Add a parameter reduction operator, currently supports min, max and sum (hysop/operator/reductions.py)

hysop_examples/examples/shear_layer/shear_layer.py

@@ -25,11 +25,11 @@ def compute(args):
     from hysop.constants import Implementation, AdvectionCriteria
 
     from hysop.operators import DirectionalAdvection, Advection, \
-        PoissonCurl, AdaptiveTimeStep,        \
+        PoissonCurl, AdaptiveTimeStep, FieldPlotter2D, \
         MinMaxFieldStatistics, StrangSplitting
 
     from hysop.methods import SpaceDiscretization, Remesh, TimeIntegrator, \
-        ComputeGranularity, Interpolation
+        ComputeGranularity, Interpolation, Backend
 
     from hysop.symbolic import space_symbols
 
@@ -164,6 +164,21 @@ def compute(args):
     adapt_dt.push_advection_criteria(lcfl=args.lcfl, Finf=min_max_W.Finf,
                                      criteria=AdvectionCriteria.W_INF)
 
+    # Field plotter
+    if args.plot_vorticity:
+        def fig_title(simulation):
+            return f'Fields at t={simulation.time:2.2e}, iteration={simulation.current_iteration}, dt={simulation.time_step:2.2e}s'
+
+        plot_fields = FieldPlotter2D(name='plot',
+               figsize=(16,6), shape=(1,3), add_colorbars=True, symmetric_cbar=True,
+               fields=(velo[0], velo[1], vorti), variables=npts, fig_title=fig_title,
+               update_frequency=args.plot_freq, save_frequency=args.plot_freq,
+               force_backend=Backend.OPENCL if impl is Implementation.OPENCL else None,
+               **extra_op_kwds)
+    else:
+        plot_fields = None
+
+
     # Create the problem we want to solve and insert our
     # directional splitting subgraph and the standard operators.
     # The method dictionnary passed to this graph will be dispatched
@@ -177,9 +192,14 @@ def compute(args):
         }
     )
     problem = Problem(method=method)
-    problem.insert(poisson, advec, min_max_U, min_max_W, adapt_dt)
+    problem.insert(poisson, advec, min_max_U, min_max_W, adapt_dt, plot_fields)
     problem.build(args)
 
+    if plot_fields is not None:
+        plot_fields.axes[0,0].set_title('Velocity Ux')
+        plot_fields.axes[0,1].set_title('Velocity Uy')
+        plot_fields.axes[0,2].set_title('Vorticity ω')
+
     # If a visu_rank was provided, and show_graph was set,
     # display the graph on the given process rank.
     if args.display_graph:
@@ -280,7 +300,7 @@ if __name__ == '__main__':
                                       help=('Plot the vorticity component during simulation. ' +
                                             'Simulation will stop at each time of interest and ' +
                                             'the plot will be updated every specified freq iterations.'))
-            graphical_io.add_argument('-pf', '--plot-freq', type=int, default=10,
+            graphical_io.add_argument('-pf', '--plot-freq', type=int, default=100,
                                       dest='plot_freq',
                                       help=('Plot frequency in terms of iterations.'
                                             + ' Use 0 to disable frequency based plotting.'))