double  mx3d_adjoint();
void mx3d_transform(double p[3], double a[3][3], double q[3]);
void mx3d_mul(double a[3][3], double b[3][3], double c[3][3]);
/*  |a b|
 *  |c d|
 */
#define DET2(a,b, c,d) ((a)*(d) - (b)*(c))