| 79 |
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#ifdef INVMAT |
| 80 |
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/* |
| 81 |
|
* invmat - computes the inverse of mat into inverse. Returns 1 |
| 82 |
< |
* if there exists an inverse, 0 otherwise. It uses Gause Elimination |
| 83 |
< |
* method. |
| 82 |
> |
* if there exists an inverse, 0 otherwise. It uses Gaussian Elimination |
| 83 |
> |
* method with partial pivoting. |
| 84 |
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*/ |
| 85 |
|
|
| 86 |
|
invmat(inverse,mat) |
| 87 |
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double mat[4][4],inverse[4][4]; |
| 88 |
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{ |
| 89 |
|
#define SWAP(a,b,t) (t=a,a=b,b=t) |
| 90 |
+ |
#define ABS(x) (x>=0?x:-(x)) |
| 91 |
|
|
| 92 |
|
register int i,j,k; |
| 93 |
|
register double temp; |
| 94 |
|
|
| 94 |
– |
setident4(inverse); |
| 95 |
|
copymat4(m4tmp, mat); |
| 96 |
+ |
setident(inverse); |
| 97 |
|
|
| 98 |
|
for(i = 0; i < 4; i++) { |
| 99 |
< |
if(m4tmp[i][i] == 0) { /* Pivot is zero */ |
| 100 |
< |
/* Look for a raw with pivot != 0 and swap raws */ |
| 101 |
< |
for(j = i + 1; j < 4; j++) |
| 102 |
< |
if(m4tmp[j][i] != 0) { |
| 103 |
< |
for( k = 0; k < 4; k++) { |
| 104 |
< |
SWAP(m4tmp[i][k],m4tmp[j][k],temp); |
| 105 |
< |
SWAP(inverse[i][k],inverse[j][k],temp); |
| 106 |
< |
} |
| 107 |
< |
break; |
| 108 |
< |
} |
| 109 |
< |
if(j == 4) /* No replacing raw -> no inverse */ |
| 110 |
< |
return(0); |
| 111 |
< |
} |
| 99 |
> |
/* Look for row with largest pivot and swap rows */ |
| 100 |
> |
temp = 0; j = -1; |
| 101 |
> |
for(k = i; k < 4; k++) |
| 102 |
> |
if(ABS(m4tmp[k][i]) > temp) { |
| 103 |
> |
temp = ABS(m4tmp[k][i]); |
| 104 |
> |
j = k; |
| 105 |
> |
} |
| 106 |
> |
if(j == -1) /* No replacing row -> no inverse */ |
| 107 |
> |
return(0); |
| 108 |
> |
if (j != i) |
| 109 |
> |
for(k = 0; k < 4; k++) { |
| 110 |
> |
SWAP(m4tmp[i][k],m4tmp[j][k],temp); |
| 111 |
> |
SWAP(inverse[i][k],inverse[j][k],temp); |
| 112 |
> |
} |
| 113 |
|
|
| 114 |
|
temp = m4tmp[i][i]; |
| 115 |
|
for(k = 0; k < 4; k++) { |
| 127 |
|
} |
| 128 |
|
} |
| 129 |
|
return(1); |
| 130 |
+ |
|
| 131 |
+ |
#undef ABS |
| 132 |
+ |
#undef SWAP |
| 133 |
|
} |
| 134 |
|
#endif |
