From 51573da3a4407288b900e8764e20de4fc09018d3 Mon Sep 17 00:00:00 2001
From: Chen-Pang He <jdh8@ms63.hinet.net>
Date: Sun, 21 Jul 2013 01:00:36 +0800
Subject: Warn about power of a matrix with non-semisimple 0 eigenvalue.

---
 unsupported/Eigen/MatrixFunctions | 4 ++++
 1 file changed, 4 insertions(+)

(limited to 'unsupported/Eigen/MatrixFunctions')

diff --git a/unsupported/Eigen/MatrixFunctions b/unsupported/Eigen/MatrixFunctions
index 41dfab390..ff466a519 100644
--- a/unsupported/Eigen/MatrixFunctions
+++ b/unsupported/Eigen/MatrixFunctions
@@ -262,6 +262,10 @@ where \f$ T_1 \f$ is invertible. Then \f$ T^p \f$ is given by
       0     & 0
     \end{array}. \right] \f]
 
+\warning Fractional power of a matrix with a non-semisimple zero
+eigenvalue is not well-defined. We introduce an assertion failure
+against inaccurate result, e.g. \include MatrixPower_failure.cpp
+
 Details of the algorithm can be found in: Nicholas J. Higham and
 Lijing Lin, "A Schur-Pad&eacute; algorithm for fractional powers of a
 matrix," <em>SIAM J. %Matrix Anal. Applic.</em>,
-- 
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