From 94cbda2d4dcd96eb51e5f076a7c9dedd2b38fb91 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20H=C3=A4hnke?=
 <11663234+DanBenHa@users.noreply.github.com>
Date: Wed, 2 Dec 2020 19:38:35 +0100
Subject: [PATCH] Fixed #286 mass absolute nan (#288)

* test mass_absolute for nan caused by float imprecision

* Min-clip values at 0 in _mass_absolute

Fixes #286
---
 stumpy/core.py     |  4 +++-
 tests/test_core.py | 60 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 63 insertions(+), 1 deletion(-)

diff --git a/stumpy/core.py b/stumpy/core.py
index dba5e8781..96bb7d3ae 100644
--- a/stumpy/core.py
+++ b/stumpy/core.py
@@ -861,7 +861,9 @@ def _mass_absolute(Q_squared, T_squared, QT):
     `See Mueen's Absolute Algorithm for Similarity Search \
     <https://www.cs.unm.edu/~mueen/MASS_absolute.m>`__
     """
-    return np.sqrt(Q_squared + T_squared - 2 * QT)
+    D = Q_squared + T_squared - 2 * QT
+    D[D < 0] = 0.0
+    return np.sqrt(D)
 
 
 def mass_absolute(Q, T):
diff --git a/tests/test_core.py b/tests/test_core.py
index 482ad79df..3361beba3 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -430,6 +430,66 @@ def test_mass_absolute_T_inf(Q, T):
     npt.assert_almost_equal(ref, comp)
 
 
+def test_mass_absolute_sqrt_input_negative():
+    Q = np.array(
+        [
+            -13.09,
+            -14.1,
+            -15.08,
+            -16.31,
+            -17.13,
+            -17.5,
+            -18.07,
+            -18.07,
+            -17.48,
+            -16.24,
+            -14.88,
+            -13.56,
+            -12.65,
+            -11.93,
+            -11.48,
+            -11.06,
+            -10.83,
+            -10.67,
+            -10.59,
+            -10.81,
+            -10.92,
+            -11.15,
+            -11.37,
+            -11.53,
+            -11.19,
+            -11.08,
+            -10.48,
+            -10.14,
+            -9.92,
+            -9.99,
+            -10.11,
+            -9.92,
+            -9.7,
+            -9.47,
+            -9.06,
+            -9.01,
+            -8.79,
+            -8.67,
+            -8.33,
+            -8.0,
+            -8.26,
+            -8.0,
+            -7.54,
+            -7.32,
+            -7.13,
+            -7.24,
+            -7.43,
+            -7.93,
+            -8.8,
+            -9.71,
+        ]
+    )
+    ref = 0
+    comp = core.mass_absolute(Q, Q)
+    npt.assert_almost_equal(ref, comp)
+
+
 def test_apply_exclusion_zone():
     T = np.array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9], dtype=float)
     ref = np.empty(T.shape)