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 896b95a6bSBarry 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> 175f748d31SJed Brown #include <petsc/private/kernels/blockinvert.h> 182bb67c89SBarry Smith 19d71ae5a4SJacob Faibussowitsch PETSC_INTERN PetscErrorCode PetscLINPACKgedi(MatScalar *a, PetscInt n, PetscInt *ipvt, MatScalar *work) 20d71ae5a4SJacob Faibussowitsch { 21690b6cddSBarry Smith PetscInt i__2, kb, kp1, nm1, i, j, k, l, ll, kn, knp1, jn1; 223f1db9ecSBarry Smith MatScalar *aa, *ax, *ay, tmp; 233f1db9ecSBarry Smith MatScalar t; 242bb67c89SBarry Smith 253a40ed3dSBarry Smith PetscFunctionBegin; 266d84be18SBarry Smith --work; 276d84be18SBarry Smith --ipvt; 2839d66777SBarry Smith a -= n + 1; 292bb67c89SBarry Smith 302bb67c89SBarry Smith /* compute inverse(u) */ 312bb67c89SBarry Smith 326d84be18SBarry Smith for (k = 1; k <= n; ++k) { 3339d66777SBarry Smith kn = k * n; 3439d66777SBarry Smith knp1 = kn + k; 3539d66777SBarry Smith a[knp1] = 1.0 / a[knp1]; 3639d66777SBarry Smith t = -a[knp1]; 372bb67c89SBarry Smith i__2 = k - 1; 3839d66777SBarry Smith aa = &a[1 + kn]; 396d84be18SBarry Smith for (ll = 0; ll < i__2; ll++) aa[ll] *= t; 402bb67c89SBarry Smith kp1 = k + 1; 416d84be18SBarry Smith if (n < kp1) continue; 426d84be18SBarry Smith ax = aa; 436d84be18SBarry Smith for (j = kp1; j <= n; ++j) { 448d3e6ddaSBarry Smith jn1 = j * n; 458d3e6ddaSBarry Smith t = a[k + jn1]; 468d3e6ddaSBarry Smith a[k + jn1] = 0.; 478d3e6ddaSBarry Smith ay = &a[1 + jn1]; 4826fbe8dcSKarl Rupp for (ll = 0; ll < k; ll++) ay[ll] += t * ax[ll]; 492bb67c89SBarry Smith } 502bb67c89SBarry Smith } 512bb67c89SBarry Smith 522bb67c89SBarry Smith /* form inverse(u)*inverse(l) */ 532bb67c89SBarry Smith 546d84be18SBarry Smith nm1 = n - 1; 55*3ba16761SJacob Faibussowitsch if (nm1 < 1) PetscFunctionReturn(PETSC_SUCCESS); 566d84be18SBarry Smith for (kb = 1; kb <= nm1; ++kb) { 576d84be18SBarry Smith k = n - kb; 5839d66777SBarry Smith kn = k * n; 592bb67c89SBarry Smith kp1 = k + 1; 6039d66777SBarry Smith aa = a + kn; 616d84be18SBarry Smith for (i = kp1; i <= n; ++i) { 626d84be18SBarry Smith work[i] = aa[i]; 636d84be18SBarry Smith aa[i] = 0.; 642bb67c89SBarry Smith } 656d84be18SBarry Smith for (j = kp1; j <= n; ++j) { 662bb67c89SBarry Smith t = work[j]; 676d84be18SBarry Smith ax = &a[j * n + 1]; 6839d66777SBarry Smith ay = &a[kn + 1]; 6926fbe8dcSKarl Rupp for (ll = 0; ll < n; ll++) ay[ll] += t * ax[ll]; 702bb67c89SBarry Smith } 712bb67c89SBarry Smith l = ipvt[k]; 722bb67c89SBarry Smith if (l != k) { 7339d66777SBarry Smith ax = &a[kn + 1]; 746d84be18SBarry Smith ay = &a[l * n + 1]; 756d84be18SBarry Smith for (ll = 0; ll < n; ll++) { 766d84be18SBarry Smith tmp = ax[ll]; 776d84be18SBarry Smith ax[ll] = ay[ll]; 786d84be18SBarry Smith ay[ll] = tmp; 792bb67c89SBarry Smith } 802bb67c89SBarry Smith } 816d84be18SBarry Smith } 82*3ba16761SJacob Faibussowitsch PetscFunctionReturn(PETSC_SUCCESS); 836d84be18SBarry Smith } 84