include math_eigen.h, remove it from .gitignore

doc/src/pg_dev_utils.rst

@@ -428,11 +428,11 @@ Eigensolver functions
 
 The ``MathEigen`` sub-namespace of the ``LAMMPS_NS`` namespace contains
 functions and classes for eigensolvers. Currently only the
-:cpp:func:`jacobi3 function <MathEigen::jacobi3(double const *const *mat, double *eval, double **evec)>`
-is used in various places in LAMMPS.  That function is built on top
-of a group of more generic eigensolvers that are maintained in the
-``math_eigen_impl.h`` header file.  This header contains the implementation
-of three template classes:
+:cpp:func:`jacobi3 function <MathEigen::jacobi3>` is used in various
+places in LAMMPS.  That function is built on top of a group of more
+generic eigensolvers that are maintained in the ``math_eigen_impl.h``
+header file.  This header contains the implementation of three template
+classes:
 
 #. "Jacobi" calculates all of the eigenvalues and eigenvectors
    of a dense, symmetric, real matrix.

src/.gitignore

@@ -33,7 +33,6 @@
 /pair_kim.h
 
 /superpose3d.h
-/math_eigen.h
 
 /kokkos.cpp
 /kokkos.h

src/math_eigen.h

@@ -0,0 +1,40 @@
+/* -*- c++ -*- ----------------------------------------------------------
+   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
+   http://lammps.sandia.gov, Sandia National Laboratories
+   Steve Plimpton, sjplimp@sandia.gov
+
+   Copyright (2003) Sandia Corporation.  Under the terms of Contract
+   DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
+   certain rights in this software.  This software is distributed under
+   the GNU General Public License.  (Some of the code in this file is also
+   available using a more premissive license.  See below for details.)
+
+   See the README file in the top-level LAMMPS directory.
+------------------------------------------------------------------------- */
+/* ----------------------------------------------------------------------
+   Contributing authors: Yuya Kurebayashi (Tohoku University, Lanczos algorithm)
+                         Andrew Jewett (Scripps Research, Jacobi algorithm)
+------------------------------------------------------------------------- */
+
+#ifndef LMP_MATH_EIGEN_H
+#define LMP_MATH_EIGEN_H
+
+namespace MathEigen {
+
+/** A specialized function which finds the eigenvalues and eigenvectors
+ *  of a 3x3 matrix (in double ** format).
+ *
+ * \param  mat   the 3x3 matrix you wish to diagonalize
+ * \param  eval  store the eigenvalues here
+ * \param  evec  store the eigenvectors here...
+ * \return       0 if eigenvalue calculation converged, 1 if it failed */
+
+int jacobi3(double const* const* mat, double *eval, double **evec);
+
+/** \overload */
+
+int jacobi3(double const mat[3][3], double *eval, double evec[3][3]);
+
+}
+
+#endif //#ifndef LMP_MATH_EIGEN_H