From 251e218bb2d780964e001d8c0eeee993f9bc9dd1 Mon Sep 17 00:00:00 2001
From: Anton Khirnov <anton@khirnov.net>
Date: Sun, 1 Dec 2019 17:13:11 +0100
Subject: horizon: add apparent horizon equations

---
 utils.py | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

(limited to 'utils.py')

diff --git a/utils.py b/utils.py
index 7440919..f0ba2f4 100644
--- a/utils.py
+++ b/utils.py
@@ -19,6 +19,24 @@ def matrix_invert(mat):
     inv = np.linalg.inv(mat)
     return inv.transpose((1, 2, 0)).reshape(oldshape)
 
+def matrix_det(mat):
+    """
+    Pointwise matrix determinant.
+
+    Given an array that stores many square matrices (e.g. the values of the
+    metric tensor at spacetime points), compute the array of corresponding
+    determinants.
+
+    :param array_like mat: N-D array with N>2 and each mat[i0, ..., :, :] a
+                           square matrix.
+    :return: Array of determinants.
+    """
+    oldshape = mat.shape
+    newshape = oldshape[:2] + (np.product(mat.shape[2:]),)
+
+    mat = mat.reshape(newshape).transpose((2, 0, 1))
+    return np.linalg.det(mat).reshape(oldshape[2:])
+
 def array_reflect(data, parity = 1.0, axis = -1):
     """
     Reflect an N-D array with respect to the specified axis. E.g. input
-- 
cgit v1.2.3