Matrix *Matrix_inverse(Matrix *mat){
double det=Matrix_determinant(mat);
if(mat->rows != mat->cols || det == 0.0){
return Matrix_create(mat->rows, mat->cols);
}
Matrix *temp = Matrix_clone(mat);
int n = temp->rows;
int m = temp->cols;
int i,j;
double tempdet,val;
Matrix *Cofactor = Matrix_create(n, m);
for(j = 0; j < m; j++){
for(i = 0; i < n; i++){
Matrix *Mintemp = Matrix_minor(temp,i, j);
tempdet = Matrix_determinant(Mintemp);
Matrix_set(Cofactor,i,j,tempdet);
}
}
Cofactor = Matrix_transpose(Cofactor);
for(i = 0; i < n; i++){
for(j = 0; j < m; j++){
val=Matrix_get(Cofactor,i,j) * pow(-1.0,(i+j)) /det;
if(isnan(val)) val=0;
Matrix_set(Cofactor,i,j, val);
//Cofactor.setValue(i, j, (Cofactor.getValue(i, j) * Math.pow(-1D, i + j + 2)) / det);
}
}
return Cofactor;
}
static void testDeterminant() {
float determinant;
determinant = Matrix_determinant(Matrix_identity());
TestCase_assert(fabs(determinant - 1.0f) < EPSILON, "Expected 1.0 but got %f", determinant);
determinant = Matrix_determinant(Matrix_init(0.0f, 0.0f, 2.0f, 2.0f,
2.0f, 0.0f, 0.0f, 3.0f,
0.0f, 2.0f, 0.0f, 1.0f,
0.0f, 0.0f, 0.0f, 1.0f));
TestCase_assert(fabs(determinant - 8.0f) < EPSILON, "Expected 8.0 but got %f", determinant);
}
void Matrix_invert(Matrix * matrix) {
float determinant;
Matrix result;
int index, indexTransposed;
int sign;
determinant = Matrix_determinant(*matrix);
for (index = 0; index < 16; index++) {
sign = 1 - (((index % 4) + (index / 4)) % 2) * 2;
indexTransposed = (index % 4) * 4 + index / 4;
result.m[indexTransposed] = Matrix_subdeterminant(*matrix, index) * sign / determinant;
}
*matrix = result;
}
