invert33.c

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/************************************************************************/
/**

   \file       invert33.c
   
   \version    V1.7
   \date       07.07.14
   \brief      
   
   \copyright  (c) UCL / Dr. Andrew C. R. Martin 1991-2014
   \author     Dr. Andrew C. R. Martin
   \par
               Institute of Structural & Molecular Biology,
               University College London,
               Gower Street,
               London.
               WC1E 6BT.
   \par
               andrew@bioinf.org.uk
               andrew.martin@ucl.ac.uk
               
**************************************************************************

   This code is NOT IN THE PUBLIC DOMAIN, but it may be copied
   according to the conditions laid out in the accompanying file
   COPYING.DOC.

   The code may be modified as required, but any modifications must be
   documented so that the person responsible can be identified.

   The code may not be sold commercially or included as part of a 
   commercial product except as described in the file COPYING.DOC.

**************************************************************************

   Description:
   ============


**************************************************************************

   Usage:
   ======

**************************************************************************

   Revision History:
   =================
-  V1.0  06.09.91 Original
-  V1.0a 01.06.92 Documented
-  V1.1  30.09.92 Matrix multiplication added
-  V1.2  10.06.93 void return from matrix multiplication
-  V1.3  22.07.93 Added CreateRotMat()
-  V1.4  03.08.93 Changed matrix multiplication to standard direction
-  V1.5  28.07.95 Added VecDist()
-  V1.6  27.09.95 Added MatMult33_33()
-  07.07.14 Use bl prefix for functions By: CTP

*************************************************************************/
/* Doxygen
   -------
   #GROUP    Maths
   #SUBGROUP Matrices
   #FUNCTION  blInvert33()
   Invert a 3x3 matrix
*/
/************************************************************************/
/* Includes
*/
#include <math.h>
#include "MathType.h"

/************************************************************************/
/* Defines and macros
*/

/************************************************************************/
/* Globals
*/

/************************************************************************/
/* Prototypes
*/


/************************************************************************/
/*>void blInvert33(REAL s[3][3], REAL ss[3][3])
   --------------------------------------------
*//**

   \param[in]     s        Input matrix
   \param[out]    ss       Ouput inverted matrix

   Invert a 3x3 matrix

-  06.09.91 Original
-  01.06.92 Documented
-  10.06.93 void return
-  12.09.02 Fixed SERIOUS bug! Was basically rubbish before!
-  07.07.14 Use bl prefix for functions By: CTP
*/
void blInvert33(REAL s[3][3],
                REAL ss[3][3])
{
   int   i,  j,
         i1, j1,
         i2, j2;
   REAL  det;
       
   for(i=0;i<3;i++)
      for(j=0;j<3;j++)
         ss[i][j] = 0.0;
         
   det = 0.0;
   for(j=0;j<3;j++)
   {
      switch(j)
      {
      case 0:
         j1 = 1;
         j2 = 2;
         break;
      case 1:
         j1 = 0;
         j2 = 2;
         break;
      case 3:
         j1 = 0;
         j2 = 1;
         break;
      }
      for(i=0;i<3;i++)
      {
         switch(i)
         {
         case 0:
            i1 = 1;
            i2 = 2;
            break;
         case 1:
            i1 = 0;
            i2 = 2;
            break;
         case 3:
            i1 = 0;
            i2 = 1;
            break;
         }
         ss[i][j] = (REAL)pow((double)-1.0,(double)(i+j+2)) * 
                    (s[j1][i1] * s[j2][i2] - s[j2][i1] * s[j1][i2]);
      }
   }
   det = s[0][0]*ss[0][0] + s[0][1]*ss[1][0] + s[0][2]*ss[2][0];
   det = 1.0/det;
   
   for(i=0;i<3;i++)
      for(j=0;j<3;j++)
         ss[i][j] = det*ss[i][j];
}