towards complete breakup implementation for GPU (most methods in TestSDMBreakup work on CUDA now) (#980)

Co-authored-by: Sylwester Arabas <[email protected]>

Author: abulenok

PySDM/attributes/physics/multiplicities.py

@@ -2,9 +2,14 @@
 super-particle multiplicity (aka weighting factor) - the number of real-world particles
  represented in the simulation with a given super particle
 """
+import numpy as np
+
 from PySDM.attributes.impl.base_attribute import BaseAttribute
 
 
 class Multiplicities(BaseAttribute):
+    TYPE = np.int64
+    MAX_VALUE = np.iinfo(TYPE).max
+
     def __init__(self, builder):
-        super().__init__(builder, name="n", dtype=int)
+        super().__init__(builder, name="n", dtype=Multiplicities.TYPE)

PySDM/backends/impl_numba/methods/collisions_methods.py

@@ -543,9 +543,9 @@ def collision_coalescence_breakup(
         is_first_in_pair,
         warn_overflows,
         volume,
+        max_multiplicity,
     ):
         # pylint: disable=too-many-locals
-        max_multiplicity = np.iinfo(multiplicity.data.dtype).max // 2e5
         self.__collision_coalescence_breakup_body(
             multiplicity=multiplicity.data,
             idx=idx.data,