1 2 /* 3 This file creating by running f2c 4 linpack. this version dated 08/14/78 5 cleve moler, university of new mexico, argonne national lab. 6 7 Computes the inverse of a matrix given its factors and pivots 8 calculated by PetscLINPACKgefa(). Performed in-place for an n by n 9 dense matrix. 10 11 Used by the sparse factorization routines in 12 src/mat/impls/baij/seq 13 14 */ 15 16 #include <petscsys.h> 17 18 PETSC_INTERN PetscErrorCode PetscLINPACKgedi(MatScalar *a,PetscInt n,PetscInt *ipvt,MatScalar *work) 19 { 20 PetscInt i__2,kb,kp1,nm1,i,j,k,l,ll,kn,knp1,jn1; 21 MatScalar *aa,*ax,*ay,tmp; 22 MatScalar t; 23 24 PetscFunctionBegin; 25 --work; 26 --ipvt; 27 a -= n + 1; 28 29 /* compute inverse(u) */ 30 31 for (k = 1; k <= n; ++k) { 32 kn = k*n; 33 knp1 = kn + k; 34 a[knp1] = 1.0 / a[knp1]; 35 t = -a[knp1]; 36 i__2 = k - 1; 37 aa = &a[1 + kn]; 38 for (ll=0; ll<i__2; ll++) aa[ll] *= t; 39 kp1 = k + 1; 40 if (n < kp1) continue; 41 ax = aa; 42 for (j = kp1; j <= n; ++j) { 43 jn1 = j*n; 44 t = a[k + jn1]; 45 a[k + jn1] = 0.; 46 ay = &a[1 + jn1]; 47 for (ll=0; ll<k; ll++) ay[ll] += t*ax[ll]; 48 } 49 } 50 51 /* form inverse(u)*inverse(l) */ 52 53 nm1 = n - 1; 54 if (nm1 < 1) { 55 PetscFunctionReturn(0); 56 } 57 for (kb = 1; kb <= nm1; ++kb) { 58 k = n - kb; 59 kn = k*n; 60 kp1 = k + 1; 61 aa = a + kn; 62 for (i = kp1; i <= n; ++i) { 63 work[i] = aa[i]; 64 aa[i] = 0.; 65 } 66 for (j = kp1; j <= n; ++j) { 67 t = work[j]; 68 ax = &a[j * n + 1]; 69 ay = &a[kn + 1]; 70 for (ll=0; ll<n; ll++) ay[ll] += t*ax[ll]; 71 } 72 l = ipvt[k]; 73 if (l != k) { 74 ax = &a[kn + 1]; 75 ay = &a[l * n + 1]; 76 for (ll=0; ll<n; ll++) { 77 tmp = ax[ll]; 78 ax[ll] = ay[ll]; 79 ay[ll] = tmp; 80 } 81 } 82 } 83 PetscFunctionReturn(0); 84 } 85 86