1a5eb4965SSatish Balay #ifdef PETSC_RCS_HEADER 2*3a40ed3dSBarry Smith static char vcid[] = "$Id: dgedi.c,v 1.6 1997/07/09 20:55:07 balay Exp bsmith $"; 36d84be18SBarry Smith #endif 46d84be18SBarry Smith 56d84be18SBarry Smith /* 66d84be18SBarry Smith This file creating by running f2c 76d84be18SBarry Smith linpack. this version dated 08/14/78 86d84be18SBarry Smith cleve moler, university of new mexico, argonne national lab. 96d84be18SBarry Smith 106d84be18SBarry Smith Computes the inverse of a matrix given its factors and pivots 116d84be18SBarry Smith calculated by Linpack_DGEFA(). 122bb67c89SBarry Smith */ 132bb67c89SBarry Smith 146d84be18SBarry Smith #include "petsc.h" 152bb67c89SBarry Smith 165615d1e5SSatish Balay #undef __FUNC__ 175615d1e5SSatish Balay #define __FUNC__ "Linpack_DGEDI" 186d84be18SBarry Smith int Linpack_DGEDI(Scalar *a,int n,int *ipvt,Scalar *work) 192bb67c89SBarry Smith { 2039d66777SBarry Smith int i__2,kb, kp1, nm1,i, j, k, l, ll,kn,knp1,jn; 216d84be18SBarry Smith Scalar t, *aa,*ax,*ay,tmp; 222bb67c89SBarry Smith 23*3a40ed3dSBarry Smith PetscFunctionBegin; 246d84be18SBarry Smith --work; 256d84be18SBarry Smith --ipvt; 2639d66777SBarry Smith a -= n + 1; 272bb67c89SBarry Smith 282bb67c89SBarry Smith /* compute inverse(u) */ 292bb67c89SBarry Smith 306d84be18SBarry Smith for (k = 1; k <= n; ++k) { 3139d66777SBarry Smith kn = k*n; 3239d66777SBarry Smith knp1 = kn + k; 3339d66777SBarry Smith a[knp1] = 1.0 / a[knp1]; 3439d66777SBarry Smith t = -a[knp1]; 352bb67c89SBarry Smith i__2 = k - 1; 3639d66777SBarry Smith aa = &a[1 + kn]; 376d84be18SBarry Smith for ( ll=0; ll<i__2; ll++ ) aa[ll] *= t; 382bb67c89SBarry Smith kp1 = k + 1; 396d84be18SBarry Smith if (n < kp1) continue; 406d84be18SBarry Smith ax = aa; 416d84be18SBarry Smith for (j = kp1; j <= n; ++j) { 4239d66777SBarry Smith jn = j*n; 4339d66777SBarry Smith t = a[k + jn]; 4439d66777SBarry Smith a[k + jn] = 0.; 4539d66777SBarry Smith ay = &a[1 + jn]; 466d84be18SBarry Smith for ( ll=0; ll<k; ll++ ) { 476d84be18SBarry Smith ay[ll] += t*ax[ll]; 482bb67c89SBarry Smith } 492bb67c89SBarry Smith } 502bb67c89SBarry Smith } 512bb67c89SBarry Smith 522bb67c89SBarry Smith /* form inverse(u)*inverse(l) */ 532bb67c89SBarry Smith 546d84be18SBarry Smith nm1 = n - 1; 552bb67c89SBarry Smith if (nm1 < 1) { 56*3a40ed3dSBarry Smith PetscFunctionReturn(0); 572bb67c89SBarry Smith } 586d84be18SBarry Smith for (kb = 1; kb <= nm1; ++kb) { 596d84be18SBarry Smith k = n - kb; 6039d66777SBarry Smith kn = k*n; 612bb67c89SBarry Smith kp1 = k + 1; 6239d66777SBarry Smith aa = a + kn; 636d84be18SBarry Smith for (i = kp1; i <= n; ++i) { 646d84be18SBarry Smith work[i] = aa[i]; 656d84be18SBarry Smith aa[i] = 0.; 662bb67c89SBarry Smith } 676d84be18SBarry Smith for (j = kp1; j <= n; ++j) { 682bb67c89SBarry Smith t = work[j]; 696d84be18SBarry Smith ax = &a[j * n + 1]; 7039d66777SBarry Smith ay = &a[kn + 1]; 716d84be18SBarry Smith for ( ll=0; ll<n; ll++ ) { 726d84be18SBarry Smith ay[ll] += t*ax[ll]; 736d84be18SBarry Smith } 742bb67c89SBarry Smith } 752bb67c89SBarry Smith l = ipvt[k]; 762bb67c89SBarry Smith if (l != k) { 7739d66777SBarry Smith ax = &a[kn + 1]; 786d84be18SBarry Smith ay = &a[l * n + 1]; 796d84be18SBarry Smith for ( ll=0; ll<n; ll++ ) { 806d84be18SBarry Smith tmp = ax[ll]; 816d84be18SBarry Smith ax[ll] = ay[ll]; 826d84be18SBarry Smith ay[ll] = tmp; 832bb67c89SBarry Smith } 842bb67c89SBarry Smith } 856d84be18SBarry Smith } 86*3a40ed3dSBarry Smith PetscFunctionReturn(0); 876d84be18SBarry Smith } 882bb67c89SBarry Smith 89