void inverse(struct var_struct * s, struct var_struct * A)
{
int i,j;
double ration;
struct var_struct temp,tempA;
makesure(A->height==A->width,8);
temp.p = 0; tempA.p = 0;
makesize(&temp, A->height, A->height);
setunit(&temp);
copy_var(A, &tempA);
makesure(1,0);
for (i=0;i<temp.height;i++) {
if (tempA.p[i][i]==0) {
for (j=i+1;j<temp.height;j++) {
if (tempA.p[j][i]!=0) {
swaprow(&tempA,i,j);
swaprow(&temp,i,j);
break;
}
}
}
if(fabs(tempA.p[i][i])<MINIMUM) {
del(&temp);
del(&tempA);
calcerr=13;
return;
}
//保证对角线元素不为零
ration=1/tempA.p[i][i];
multrow(&tempA,i,ration);
multrow(&temp,i,ration);
for (j=i+1;j<temp.height;j++) {
ration=-tempA.p[j][i];
plusrow(&tempA,i,j,ration);
plusrow(&temp,i,j,ration);
}
}
//现已变成对角线元素为1的上三角阵
for (i=0;i<temp.height;i++) {
for (j=0;j<i;j++) {
ration=-tempA.p[j][i];
plusrow(&tempA,i,j,ration);
plusrow(&temp,i,j,ration);
}
}
copy_var(&temp,s);
del(&temp);
del(&tempA);
}
il_mat il_mat_invert(il_mat a)
{
il_mat res = il_mat_identity();
// for every column ..
for (int col = 0; col < 4; ++col) {
float diagonalfield = a.data[col*4+col];
// if we have a weird matrix with zero on the diagonal ..
float eps = 0.0001;
if (fabs(diagonalfield) < eps) {
// SIIIGH.
// Okay, let's go hunting for a row with a better diagonal to use
// keep in mind, row swapping is also a linear operation!
for (int row = 0; row < 4; ++row) if (row != col) if (fabs(a.data[row*4+col]) >= eps) {
swaprow(&a, row, col);
swaprow(&res,row, col);
}
diagonalfield = a.data[col*4+col]; // recompute
// if it still fails, we probably have a denatured matrix and are proper f****d.
assert(fabs(diagonalfield) >= eps);
}
// for every row ..
for (int row = 0; row < 4; ++row) {
// if it's not on the diagonal ..
if (row != col) {
float field = a.data[row*4+col];
// bring this field to 0 by subtracting the row that's on the diagonal for this column
addrow(&a, /* src */ col, /* dst */ row, /* factor */ -field/diagonalfield);
// do the same to identity
addrow(&res,/* src */ col, /* dst */ row, /* factor */ -field/diagonalfield);
}
}
// and finally, bring the diagonal to 1
mulrow(&a, col, 1/diagonalfield);
mulrow(&res,col, 1/diagonalfield);
}
// Success! Because a is now id, res is now a^-1. Math is fun!
return res;
}
double envalue(struct var_struct * s)
{
int i,j,flag;
double result,ration;
struct var_struct temp;
if(calcerr) return 0;
if(s->height!=s->width) {
calcerr=8;
return 0;
}
temp.p = 0;
copy_var(s, &temp);
if(calcerr) return 0;
result=1;
for (i=0;i<temp.height;i++) {
if (temp.p[i][i]==0) {
flag=0;
for (j=i+1;j<temp.height;j++) {
if (temp.p[j][i]!=0) {
swaprow(&temp,i,j);
result*=-1;
flag=1;
break;
}
}
}
if (fabs(temp.p[i][i])<MINIMUM) {
del(&temp);
return 0;
}
//保证对角线元素不为零
for (j=i+1;j<temp.height;j++) {
ration=-temp.p[j][i]/temp.p[i][i];
plusrow(&temp,i,j,ration);
}
result*=temp.p[i][i];
}
del(&temp);
return result;
}
