Merge pull request #137 from dstansby/bg-overwrite

Prevent bg being modified in place

Author: dstansby

doc/source/changes.rst

@@ -1,6 +1,12 @@
 Changelog
 =========
 
+0.4.2
+-----
+
+- Fix a bug where :class`pfsspy.tracing.FotranTracer` would overwrite the
+  magnetic field values in an :class:`~pfsspy.Output` each time it was used.
+
 0.4.1
 -----
 

pfsspy/__init__.py

@@ -362,7 +362,9 @@ def bg(self):
             bpg[i, :, :] /= (Sbp[:-1, :-1] + Sbp[1:, :-1] +
                              Sbp[1:, 1:] + Sbp[:-1, 1:])
         bsg *= -1
-        return np.stack((bpg, bsg, brg), axis=-1)
+        out = np.stack((bpg, bsg, brg), axis=-1)
+        out.flags.writeable = False
+        return out
 
     def _common_b(self):
         """

pfsspy/tracing.py

@@ -78,7 +78,7 @@ def trace(self, seeds, output):
         self.validate_seeds_shape(seeds)
 
         # The indexing order on the last index is (phi, s, r)
-        vectors = output.bg
+        vectors = output.bg.copy()
 
         # Correct s direction for coordinate system distortion
         sqrtsg = output.grid._sqrtsg_correction