| 59 |
|
p3a[1] += m4[3][1]; |
| 60 |
|
p3a[2] += m4[3][2]; |
| 61 |
|
} |
| 62 |
– |
|
| 63 |
– |
|
| 64 |
– |
/* |
| 65 |
– |
* invmat - computes the inverse of mat into inverse. Returns 1 |
| 66 |
– |
* if there exists an inverse, 0 otherwise. It uses Gaussian Elimination |
| 67 |
– |
* method with partial pivoting. |
| 68 |
– |
*/ |
| 69 |
– |
|
| 70 |
– |
invmat(inverse,mat) |
| 71 |
– |
MAT4 mat, inverse; |
| 72 |
– |
{ |
| 73 |
– |
#define SWAP(a,b,t) (t=a,a=b,b=t) |
| 74 |
– |
#define ABS(x) (x>=0?x:-(x)) |
| 75 |
– |
|
| 76 |
– |
register int i,j,k; |
| 77 |
– |
register double temp; |
| 78 |
– |
|
| 79 |
– |
copymat4(m4tmp, mat); |
| 80 |
– |
setident4(inverse); |
| 81 |
– |
|
| 82 |
– |
for(i = 0; i < 4; i++) { |
| 83 |
– |
/* Look for row with largest pivot and swap rows */ |
| 84 |
– |
temp = 0; j = -1; |
| 85 |
– |
for(k = i; k < 4; k++) |
| 86 |
– |
if(ABS(m4tmp[k][i]) > temp) { |
| 87 |
– |
temp = ABS(m4tmp[k][i]); |
| 88 |
– |
j = k; |
| 89 |
– |
} |
| 90 |
– |
if(j == -1) /* No replacing row -> no inverse */ |
| 91 |
– |
return(0); |
| 92 |
– |
if (j != i) |
| 93 |
– |
for(k = 0; k < 4; k++) { |
| 94 |
– |
SWAP(m4tmp[i][k],m4tmp[j][k],temp); |
| 95 |
– |
SWAP(inverse[i][k],inverse[j][k],temp); |
| 96 |
– |
} |
| 97 |
– |
|
| 98 |
– |
temp = m4tmp[i][i]; |
| 99 |
– |
for(k = 0; k < 4; k++) { |
| 100 |
– |
m4tmp[i][k] /= temp; |
| 101 |
– |
inverse[i][k] /= temp; |
| 102 |
– |
} |
| 103 |
– |
for(j = 0; j < 4; j++) { |
| 104 |
– |
if(j != i) { |
| 105 |
– |
temp = m4tmp[j][i]; |
| 106 |
– |
for(k = 0; k < 4; k++) { |
| 107 |
– |
m4tmp[j][k] -= m4tmp[i][k]*temp; |
| 108 |
– |
inverse[j][k] -= inverse[i][k]*temp; |
| 109 |
– |
} |
| 110 |
– |
} |
| 111 |
– |
} |
| 112 |
– |
} |
| 113 |
– |
return(1); |
| 114 |
– |
|
| 115 |
– |
#undef ABS |
| 116 |
– |
#undef SWAP |
| 117 |
– |
} |
