Added documentation

Cantera/src/equil/vcs_internal.h

@@ -158,6 +158,40 @@ namespace VCSnonideal {
    */
   int  vcsUtil_mlequ(double *c, int idem, int n, double *b, int m);
 
+  //! Invert an n x n matrix and solve m rhs's
+  /*!
+   * Solve a square matrix with multiple right hand sides
+   *
+   * \f[
+   *     C X + B = 0;
+   * \f]
+   *
+   * This routine uses Gauss-Jordan elimination and is optimized for the solution
+   * of lots of rhs's. Full row and column pivoting is used here. It's been
+   * shown to be necessary in at least one case. 
+   * The matrix C is destroyed during the solve.
+   *
+   * @return  The solution x[] is returned in the matrix <I>B</I>.
+   *          Routine returns an integer representing success:
+   *     -   1 : Matrix is singluar
+   *     -   0 : solution is OK
+   *   
+   *  @param c  Matrix to be inverted. c is in fortran format, i.e., rows
+   *            are the inner loop. Row  numbers equal to idem.
+   *            c[i+j*idem] = c_i_j = Matrix to be inverted:
+   *                   -  i = row number
+   *                   -  j = column number
+   *
+   *  @param idem number of row dimensions in c
+   *  @param n  Number of rows and columns in c
+   *  @param b  Multiple RHS. Note, b is actually the negative of 
+   *            most formulations.  Row  numbers equal to idem.
+   *             b[i+j*idem] = b_i_j = vectors of rhs's:
+   *                   -  i = row number
+   *                   -  j = column number
+   *            (each column is a new rhs)
+   *  @param m  number of rhs's
+   */
   int vcsUtil_gaussj(double *c, int idem, int n, double *b, int m);
 
   //! Swap values in vector of doubles