Python tools: function for block decomposition

python/waLBerla/tools/config/__init__.py

+from .prm_files import toPrm, fromPrm
+from .setup import block_decomposition
+
+__all__ = ['toPrm', 'fromPrm', 'block_decomposition']

python/waLBerla/tools/config/setup.py

+def _factors(n):
+    while n > 1:
+        for i in range(2, n + 1):
+            if n % i == 0:
+                n //= i
+                yield i
+                break
+
+
+def block_decomposition(processes):
+    """Compute a 3D factorization of 'processes' in a 3 factors returned as tuple"""
+    result = [1, 1, 1]
+    for factor in _factors(processes):
+        min_idx = result.index(min(result))
+        result[min_idx] *= factor
+    assert result[0] * result[1] * result[2] == processes
+    return tuple(result)