/* mxmt.f -- translated by f2c (version 19980913).
   You must link the resulting object file with the libraries:
	-lf2c -lm   (in that order)
*/

#include "f2c.h"

/* Table of constant values */

static integer c__9 = 9;

/* $Procedure      MXMT ( Matrix times matrix transpose, 3x3 ) */
/* Subroutine */ int mxmt_(doublereal *m1, doublereal *m2, doublereal *mout)
{
    /* System generated locals */
    integer i__1, i__2, i__3, i__4, i__5, i__6, i__7;

    /* Builtin functions */
    integer s_rnge(char *, integer, char *, integer);

    /* Local variables */
    integer i__, j;
    extern /* Subroutine */ int moved_(doublereal *, integer *, doublereal *);
    doublereal prodm[9]	/* was [3][3] */;

/* $ Abstract */

/*      Multiply a 3x3 matrix and the transpose of another 3x3 matrix. */

/* $ Disclaimer */

/*     THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/*     CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/*     GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/*     ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/*     PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/*     TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/*     WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/*     PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/*     SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/*     SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */

/*     IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/*     BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/*     LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/*     INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/*     REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/*     REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */

/*     RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/*     THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/*     CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/*     ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */

/* $ Required_Reading */

/*      None. */

/* $ Keywords */

/*      MATRIX */

/* $ Declarations */
/* $ Brief_I/O */

/*      VARIABLE  I/O  DESCRIPTION */
/*      --------  ---  -------------------------------------------------- */
/*      M1         I   3x3 double precision matrix. */
/*      M2         I   3x3 double precision matrix. */
/*      MOUT       O   3x3 double precision matrix. MOUT is the */
/*                     M1 * M2**T. */

/* $ Detailed_Input */

/*      M1         is an arbitrary 3x3 double precision matrix. */

/*      M2         is an arbitrary 3x3 double precision matrix. */
/*                 Typically, M2 will be a rotation matrix since */
/*                 then its transpose is its inverse (but this is */
/*                 NOT a requirement). */

/* $ Detailed_Output */

/*      MOUT       is a 3x3 double precision matrix. MOUT is the */
/*                 product (M1) x (M2**T). MOUT can overwrite M1 or M2. */

/* $ Parameters */

/*      None. */

/* $ Particulars */

/*      The code reflects precisely the following mathematical expression */

/*      For each value of the subscripts I and J from 1 to 3: */

/*      MOUT(I,J) = Summation from K=1 to 3 of  ( M1(I,K) * M2(J,K) ) */

/*      Note that the reversal of the K and J subscripts in the right- */
/*      hand matrix M2 is what makes MOUT the product of the TRANSPOSE */
/*      of M2 and not simply of M2 itself.  Also, the intermediate */
/*      results of the operation above are buffered in a temporary matrix */
/*      which is later moved to the output matrix.  Thus, to save space */
/*      in the calling program, MOUT can be actually be M2 or M1 if */
/*      desired without interfering with the computations. */

/* $ Examples */

/*      Let M1 = |  0.0D0  1.0D0  0.0D0 | */
/*               |                      | */
/*               | -1.0D0  0.0D0  0.0D0 | */
/*               |                      | */
/*               |  0.0D0  0.0D0  1.0D0 | */


/*          M2 = |  0.0D0  1.0D0  0.0D0 | */
/*               |                      | */
/*               | -1.0D0  0.0D0  0.0D0 | */
/*               |                      | */
/*               |  0.0D0  0.0D0  1.0D0 | */

/*      then the call */

/*      CALL MXMT ( M1, M2, MOUT ) */

/*      produces the matrix */


/*        MOUT = | 1.0D0  0.0D0  0.0D0 | */
/*               |                     | */
/*               | 0.0D0  1.0D0  0.0D0 | */
/*               |                     | */
/*               | 0.0D0  0.0D0  1.0D0 | */


/* $ Restrictions */

/*      The user is responsible for checking the magnitudes of the */
/*      elements of M1 and M2 so that a floating point overflow does */
/*      not occur.  (In the typical use where M1 and M2 are rotation */
/*      matrices, this not a risk at all.) */

/* $ Exceptions */

/*     Error free. */

/* $ Files */

/*      None. */

/* $ Author_and_Institution */

/*      W.M. Owen       (JPL) */

/* $ Literature_References */

/*      None */

/* $ Version */

/* -    SPICELIB Version 1.0.1, 10-MAR-1992 (WLT) */

/*        Comment section for permuted index source lines was added */
/*        following the header. */

/* -    SPICELIB Version 1.0.0, 31-JAN-1990 (WMO) */

/* -& */
/* $ Index_Entries */

/*     matrix times matrix_transpose 3x3_case */

/* -& */

/*  Perform the matrix multiplication */

    for (i__ = 1; i__ <= 3; ++i__) {
	for (j = 1; j <= 3; ++j) {
	    prodm[(i__1 = i__ + j * 3 - 4) < 9 && 0 <= i__1 ? i__1 : s_rnge(
		    "prodm", i__1, "mxmt_", (ftnlen)168)] = m1[(i__2 = i__ - 
		    1) < 9 && 0 <= i__2 ? i__2 : s_rnge("m1", i__2, "mxmt_", (
		    ftnlen)168)] * m2[(i__3 = j - 1) < 9 && 0 <= i__3 ? i__3 :
		     s_rnge("m2", i__3, "mxmt_", (ftnlen)168)] + m1[(i__4 = 
		    i__ + 2) < 9 && 0 <= i__4 ? i__4 : s_rnge("m1", i__4, 
		    "mxmt_", (ftnlen)168)] * m2[(i__5 = j + 2) < 9 && 0 <= 
		    i__5 ? i__5 : s_rnge("m2", i__5, "mxmt_", (ftnlen)168)] + 
		    m1[(i__6 = i__ + 5) < 9 && 0 <= i__6 ? i__6 : s_rnge(
		    "m1", i__6, "mxmt_", (ftnlen)168)] * m2[(i__7 = j + 5) < 
		    9 && 0 <= i__7 ? i__7 : s_rnge("m2", i__7, "mxmt_", (
		    ftnlen)168)];
	}
    }

/*  Move the result into MOUT */

    moved_(prodm, &c__9, mout);

    return 0;
} /* mxmt_ */

