From 9886993d1d279f91866cf66099ede1efd57311e4 Mon Sep 17 00:00:00 2001
From: Matthew Smith <mjsmith6@illinois.edu>
Date: Fri, 15 Oct 2021 12:40:04 -0500
Subject: [PATCH] add comment explaining why abs() is outside of the sum
---
grudge/reductions.py | 2 ++
1 file changed, 2 insertions(+)
diff --git a/grudge/reductions.py b/grudge/reductions.py
index 6ec71c1d..5e8b4da7 100644
--- a/grudge/reductions.py
+++ b/grudge/reductions.py
@@ -80,6 +80,8 @@ def _norm(dcoll: DiscretizationCollection, vec, p, dd):
return np.fabs(vec)
if p == 2:
from grudge.op import _apply_mass_operator
+ # Quantities being summed are real up to rounding error, so abs() can go on
+ # the outside
return abs(
nodal_sum(
dcoll,
--
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