1be1d678aSKris Buschelman 26d84be18SBarry Smith /* 36d84be18SBarry Smith This file creating by running f2c 46d84be18SBarry Smith linpack. this version dated 08/14/78 56d84be18SBarry Smith cleve moler, university of new mexico, argonne national lab. 66d84be18SBarry Smith 76d84be18SBarry Smith Computes the inverse of a matrix given its factors and pivots 8*96b95a6bSBarry Smith calculated by PetscLINPACKgefa(). Performed in-place for an n by n 99d8b60e5SBarry Smith dense matrix. 109d8b60e5SBarry Smith 119d8b60e5SBarry Smith Used by the sparse factorization routines in 12dd882469SBarry Smith src/mat/impls/baij/seq 1371c5468dSBarry Smith 142bb67c89SBarry Smith */ 152bb67c89SBarry Smith 16c6db04a5SJed Brown #include <petscsys.h> 172bb67c89SBarry Smith 184a2ae208SSatish Balay #undef __FUNCT__ 19*96b95a6bSBarry Smith #define __FUNCT__ "PetscLINPACKgedi" 20*96b95a6bSBarry Smith PetscErrorCode PetscLINPACKgedi(MatScalar *a,PetscInt n,PetscInt *ipvt,MatScalar *work) 212bb67c89SBarry Smith { 22690b6cddSBarry Smith PetscInt i__2,kb,kp1,nm1,i,j,k,l,ll,kn,knp1,jn1; 233f1db9ecSBarry Smith MatScalar *aa,*ax,*ay,tmp; 243f1db9ecSBarry Smith MatScalar t; 252bb67c89SBarry Smith 263a40ed3dSBarry Smith PetscFunctionBegin; 276d84be18SBarry Smith --work; 286d84be18SBarry Smith --ipvt; 2939d66777SBarry Smith a -= n + 1; 302bb67c89SBarry Smith 312bb67c89SBarry Smith /* compute inverse(u) */ 322bb67c89SBarry Smith 336d84be18SBarry Smith for (k = 1; k <= n; ++k) { 3439d66777SBarry Smith kn = k*n; 3539d66777SBarry Smith knp1 = kn + k; 3639d66777SBarry Smith a[knp1] = 1.0 / a[knp1]; 3739d66777SBarry Smith t = -a[knp1]; 382bb67c89SBarry Smith i__2 = k - 1; 3939d66777SBarry Smith aa = &a[1 + kn]; 406d84be18SBarry Smith for (ll=0; ll<i__2; ll++) aa[ll] *= t; 412bb67c89SBarry Smith kp1 = k + 1; 426d84be18SBarry Smith if (n < kp1) continue; 436d84be18SBarry Smith ax = aa; 446d84be18SBarry Smith for (j = kp1; j <= n; ++j) { 458d3e6ddaSBarry Smith jn1 = j*n; 468d3e6ddaSBarry Smith t = a[k + jn1]; 478d3e6ddaSBarry Smith a[k + jn1] = 0.; 488d3e6ddaSBarry Smith ay = &a[1 + jn1]; 496d84be18SBarry Smith for (ll=0; ll<k; ll++) { 506d84be18SBarry Smith ay[ll] += t*ax[ll]; 512bb67c89SBarry Smith } 522bb67c89SBarry Smith } 532bb67c89SBarry Smith } 542bb67c89SBarry Smith 552bb67c89SBarry Smith /* form inverse(u)*inverse(l) */ 562bb67c89SBarry Smith 576d84be18SBarry Smith nm1 = n - 1; 582bb67c89SBarry Smith if (nm1 < 1) { 593a40ed3dSBarry Smith PetscFunctionReturn(0); 602bb67c89SBarry Smith } 616d84be18SBarry Smith for (kb = 1; kb <= nm1; ++kb) { 626d84be18SBarry Smith k = n - kb; 6339d66777SBarry Smith kn = k*n; 642bb67c89SBarry Smith kp1 = k + 1; 6539d66777SBarry Smith aa = a + kn; 666d84be18SBarry Smith for (i = kp1; i <= n; ++i) { 676d84be18SBarry Smith work[i] = aa[i]; 686d84be18SBarry Smith aa[i] = 0.; 692bb67c89SBarry Smith } 706d84be18SBarry Smith for (j = kp1; j <= n; ++j) { 712bb67c89SBarry Smith t = work[j]; 726d84be18SBarry Smith ax = &a[j * n + 1]; 7339d66777SBarry Smith ay = &a[kn + 1]; 746d84be18SBarry Smith for (ll=0; ll<n; ll++) { 756d84be18SBarry Smith ay[ll] += t*ax[ll]; 766d84be18SBarry Smith } 772bb67c89SBarry Smith } 782bb67c89SBarry Smith l = ipvt[k]; 792bb67c89SBarry Smith if (l != k) { 8039d66777SBarry Smith ax = &a[kn + 1]; 816d84be18SBarry Smith ay = &a[l * n + 1]; 826d84be18SBarry Smith for (ll=0; ll<n; ll++) { 836d84be18SBarry Smith tmp = ax[ll]; 846d84be18SBarry Smith ax[ll] = ay[ll]; 856d84be18SBarry Smith ay[ll] = tmp; 862bb67c89SBarry Smith } 872bb67c89SBarry Smith } 886d84be18SBarry Smith } 893a40ed3dSBarry Smith PetscFunctionReturn(0); 906d84be18SBarry Smith } 912bb67c89SBarry Smith 92