更改了bellhop.py文件中，nbeams的数目。

更改了czcore.py文件中，会聚区计算时进行并行运算。

pyat/bellhop.py

@@ -96,7 +96,7 @@ def call_Bellhop(freq, sd, rd, bathm, ssp, sed, base):
     bdy = Bndry(top, bottom)
     # Beam params
     run_type = 'C'  # incoherently sum beams, see AT docs for more info
-    nbeams = 0
+    nbeams = 3000
     alpha = np.linspace(-45, 45, 2)  # min and max launch angle -20 degrees to 20 degrees
     box = Box(Zmax, max(bathm.r))  # bound the region you let the beams go, depth in meters and range in km
     deltas = 0  # length step of ray trace, 0 means automatically choose