int fac4(int n,int m){
if(n==m) return n;
else{
int mid=(m-n)/2;
int x=fac4(n,mid+n);
int y=fac4(mid+n+1,m);
return x*y;
}
}
inline mat4 inverse(mat4 const& m)
{
float coef00 = m[2][2] * m[3][3] - m[3][2] * m[2][3];
float coef02 = m[1][2] * m[3][3] - m[3][2] * m[1][3];
float coef03 = m[1][2] * m[2][3] - m[2][2] * m[1][3];
float coef04 = m[2][1] * m[3][3] - m[3][1] * m[2][3];
float coef06 = m[1][1] * m[3][3] - m[3][1] * m[1][3];
float coef07 = m[1][1] * m[2][3] - m[2][1] * m[1][3];
float coef08 = m[2][1] * m[3][2] - m[3][1] * m[2][2];
float coef10 = m[1][1] * m[3][2] - m[3][1] * m[1][2];
float coef11 = m[1][1] * m[2][2] - m[2][1] * m[1][2];
float coef12 = m[2][0] * m[3][3] - m[3][0] * m[2][3];
float coef14 = m[1][0] * m[3][3] - m[3][0] * m[1][3];
float coef15 = m[1][0] * m[2][3] - m[2][0] * m[1][3];
float coef16 = m[2][0] * m[3][2] - m[3][0] * m[2][2];
float coef18 = m[1][0] * m[3][2] - m[3][0] * m[1][2];
float coef19 = m[1][0] * m[2][2] - m[2][0] * m[1][2];
float coef20 = m[2][0] * m[3][1] - m[3][0] * m[2][1];
float coef22 = m[1][0] * m[3][1] - m[3][0] * m[1][1];
float coef23 = m[1][0] * m[2][1] - m[2][0] * m[1][1];
vec4 fac0(coef00, coef00, coef02, coef03);
vec4 fac1(coef04, coef04, coef06, coef07);
vec4 fac2(coef08, coef08, coef10, coef11);
vec4 fac3(coef12, coef12, coef14, coef15);
vec4 fac4(coef16, coef16, coef18, coef19);
vec4 fac5(coef20, coef20, coef22, coef23);
vec4 v0(m[1][0], m[0][0], m[0][0], m[0][0]);
vec4 v1(m[1][1], m[0][1], m[0][1], m[0][1]);
vec4 v2(m[1][2], m[0][2], m[0][2], m[0][2]);
vec4 v3(m[1][3], m[0][3], m[0][3], m[0][3]);
vec4 inv0(v1 * fac0 - v2 * fac1 + v3 * fac2);
vec4 inv1(v0 * fac0 - v2 * fac3 + v3 * fac4);
vec4 inv2(v0 * fac1 - v1 * fac3 + v3 * fac5);
vec4 inv3(v0 * fac2 - v1 * fac4 + v2 * fac5);
vec4 signA(+1, -1, +1, -1);
vec4 signB(-1, +1, -1, +1);
mat4 inv(inv0 * signA, inv1 * signB, inv2 * signA, inv3 * signB);
vec4 row0(inv[0][0], inv[1][0], inv[2][0], inv[3][0]);
vec4 dot0(m[0] * row0);
float dot1 = (dot0.x + dot0.y) + (dot0.z + dot0.w);
float one_over_det = 1.f / dot1;
return inv * one_over_det;
}
