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 199371c9d4SSatish Balay PETSC_INTERN PetscErrorCode PetscLINPACKgedi(MatScalar *a, PetscInt n, PetscInt *ipvt, MatScalar *work) { 20690b6cddSBarry Smith PetscInt i__2, kb, kp1, nm1, i, j, k, l, ll, kn, knp1, jn1; 213f1db9ecSBarry Smith MatScalar *aa, *ax, *ay, tmp; 223f1db9ecSBarry Smith MatScalar t; 232bb67c89SBarry Smith 243a40ed3dSBarry Smith PetscFunctionBegin; 256d84be18SBarry Smith --work; 266d84be18SBarry Smith --ipvt; 2739d66777SBarry Smith a -= n + 1; 282bb67c89SBarry Smith 292bb67c89SBarry Smith /* compute inverse(u) */ 302bb67c89SBarry Smith 316d84be18SBarry Smith for (k = 1; k <= n; ++k) { 3239d66777SBarry Smith kn = k * n; 3339d66777SBarry Smith knp1 = kn + k; 3439d66777SBarry Smith a[knp1] = 1.0 / a[knp1]; 3539d66777SBarry Smith t = -a[knp1]; 362bb67c89SBarry Smith i__2 = k - 1; 3739d66777SBarry Smith aa = &a[1 + kn]; 386d84be18SBarry Smith for (ll = 0; ll < i__2; ll++) aa[ll] *= t; 392bb67c89SBarry Smith kp1 = k + 1; 406d84be18SBarry Smith if (n < kp1) continue; 416d84be18SBarry Smith ax = aa; 426d84be18SBarry Smith for (j = kp1; j <= n; ++j) { 438d3e6ddaSBarry Smith jn1 = j * n; 448d3e6ddaSBarry Smith t = a[k + jn1]; 458d3e6ddaSBarry Smith a[k + jn1] = 0.; 468d3e6ddaSBarry Smith ay = &a[1 + jn1]; 4726fbe8dcSKarl Rupp for (ll = 0; ll < k; ll++) ay[ll] += t * ax[ll]; 482bb67c89SBarry Smith } 492bb67c89SBarry Smith } 502bb67c89SBarry Smith 512bb67c89SBarry Smith /* form inverse(u)*inverse(l) */ 522bb67c89SBarry Smith 536d84be18SBarry Smith nm1 = n - 1; 54*ad540459SPierre Jolivet if (nm1 < 1) PetscFunctionReturn(0); 556d84be18SBarry Smith for (kb = 1; kb <= nm1; ++kb) { 566d84be18SBarry Smith k = n - kb; 5739d66777SBarry Smith kn = k * n; 582bb67c89SBarry Smith kp1 = k + 1; 5939d66777SBarry Smith aa = a + kn; 606d84be18SBarry Smith for (i = kp1; i <= n; ++i) { 616d84be18SBarry Smith work[i] = aa[i]; 626d84be18SBarry Smith aa[i] = 0.; 632bb67c89SBarry Smith } 646d84be18SBarry Smith for (j = kp1; j <= n; ++j) { 652bb67c89SBarry Smith t = work[j]; 666d84be18SBarry Smith ax = &a[j * n + 1]; 6739d66777SBarry Smith ay = &a[kn + 1]; 6826fbe8dcSKarl Rupp for (ll = 0; ll < n; ll++) ay[ll] += t * ax[ll]; 692bb67c89SBarry Smith } 702bb67c89SBarry Smith l = ipvt[k]; 712bb67c89SBarry Smith if (l != k) { 7239d66777SBarry Smith ax = &a[kn + 1]; 736d84be18SBarry Smith ay = &a[l * n + 1]; 746d84be18SBarry Smith for (ll = 0; ll < n; ll++) { 756d84be18SBarry Smith tmp = ax[ll]; 766d84be18SBarry Smith ax[ll] = ay[ll]; 776d84be18SBarry Smith ay[ll] = tmp; 782bb67c89SBarry Smith } 792bb67c89SBarry Smith } 806d84be18SBarry Smith } 813a40ed3dSBarry Smith PetscFunctionReturn(0); 826d84be18SBarry Smith } 83