1be1d678aSKris Buschelman 2a97b7df5SSatish Balay /* 39fd41dd0SBarry Smith This routine was converted by f2c from Linpack source 49fd41dd0SBarry Smith linpack. this version dated 08/14/78 59fd41dd0SBarry Smith cleve moler, university of new mexico, argonne national lab. 659539b86SBarry Smith 759539b86SBarry Smith Does an LU factorization with partial pivoting of a dense 89d8b60e5SBarry Smith n by n matrix. 99d8b60e5SBarry Smith 109d8b60e5SBarry Smith Used by the sparse factorization routines in 11dd882469SBarry Smith src/mat/impls/baij/seq 1259539b86SBarry Smith 139fd41dd0SBarry Smith */ 14c6db04a5SJed Brown #include <petscsys.h> 159fd41dd0SBarry Smith 164a2ae208SSatish Balay #undef __FUNCT__ 1796b95a6bSBarry Smith #define __FUNCT__ "PetscLINPACKgefa" 18db87b0f2SBarry Smith PETSC_INTERN PetscErrorCode PetscLINPACKgefa(MatScalar *a,PetscInt n,PetscInt *ipvt,PetscBool allowzeropivot,PetscBool *zeropivotdetected) 199fd41dd0SBarry Smith { 20690b6cddSBarry Smith PetscInt i__2,i__3,kp1,nm1,j,k,l,ll,kn,knp1,jn1; 213f1db9ecSBarry Smith MatScalar t,*ax,*ay,*aa; 22329f5518SBarry Smith MatReal tmp,max; 239fd41dd0SBarry Smith 243a40ed3dSBarry Smith PetscFunctionBegin; 255f8bbccaSHong Zhang if (zeropivotdetected) *zeropivotdetected = PETSC_FALSE; 265f8bbccaSHong Zhang 279fd41dd0SBarry Smith /* Parameter adjustments */ 289fd41dd0SBarry Smith --ipvt; 2939d66777SBarry Smith a -= n + 1; 309fd41dd0SBarry Smith 319fd41dd0SBarry Smith /* Function Body */ 329fd41dd0SBarry Smith nm1 = n - 1; 3339d66777SBarry Smith for (k = 1; k <= nm1; ++k) { 349fd41dd0SBarry Smith kp1 = k + 1; 3539d66777SBarry Smith kn = k*n; 3639d66777SBarry Smith knp1 = k*n + k; 379fd41dd0SBarry Smith 389fd41dd0SBarry Smith /* find l = pivot index */ 399fd41dd0SBarry Smith 409fd41dd0SBarry Smith i__2 = n - k + 1; 4139d66777SBarry Smith aa = &a[knp1]; 429fd41dd0SBarry Smith max = PetscAbsScalar(aa[0]); 439fd41dd0SBarry Smith l = 1; 449fd41dd0SBarry Smith for (ll=1; ll<i__2; ll++) { 459fd41dd0SBarry Smith tmp = PetscAbsScalar(aa[ll]); 469fd41dd0SBarry Smith if (tmp > max) { max = tmp; l = ll+1;} 479fd41dd0SBarry Smith } 489fd41dd0SBarry Smith l += k - 1; 499fd41dd0SBarry Smith ipvt[k] = l; 509fd41dd0SBarry Smith 515f8bbccaSHong Zhang if (a[l + kn] == 0.0) { 525f8bbccaSHong Zhang if (allowzeropivot) { 535f8bbccaSHong Zhang PetscErrorCode ierr; 545f8bbccaSHong Zhang ierr = PetscInfo1(NULL,"Zero pivot, row %D\n",k-1);CHKERRQ(ierr); 55*70d8d27cSBarry Smith if (zeropivotdetected) *zeropivotdetected = PETSC_TRUE; 565f8bbccaSHong Zhang } else SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_MAT_LU_ZRPVT,"Zero pivot, row %D",k-1); 575f8bbccaSHong Zhang } 589fd41dd0SBarry Smith 599fd41dd0SBarry Smith /* interchange if necessary */ 609fd41dd0SBarry Smith if (l != k) { 6139d66777SBarry Smith t = a[l + kn]; 6239d66777SBarry Smith a[l + kn] = a[knp1]; 6339d66777SBarry Smith a[knp1] = t; 649fd41dd0SBarry Smith } 659fd41dd0SBarry Smith 669fd41dd0SBarry Smith /* compute multipliers */ 6739d66777SBarry Smith t = -1. / a[knp1]; 689fd41dd0SBarry Smith i__2 = n - k; 6939d66777SBarry Smith aa = &a[1 + knp1]; 7026fbe8dcSKarl Rupp for (ll=0; ll<i__2; ll++) aa[ll] *= t; 719fd41dd0SBarry Smith 729fd41dd0SBarry Smith /* row elimination with column indexing */ 7339d66777SBarry Smith ax = aa; 749fd41dd0SBarry Smith for (j = kp1; j <= n; ++j) { 758d3e6ddaSBarry Smith jn1 = j*n; 768d3e6ddaSBarry Smith t = a[l + jn1]; 779fd41dd0SBarry Smith if (l != k) { 788d3e6ddaSBarry Smith a[l + jn1] = a[k + jn1]; 798d3e6ddaSBarry Smith a[k + jn1] = t; 809fd41dd0SBarry Smith } 819fd41dd0SBarry Smith 829fd41dd0SBarry Smith i__3 = n - k; 838d3e6ddaSBarry Smith ay = &a[1+k+jn1]; 8426fbe8dcSKarl Rupp for (ll=0; ll<i__3; ll++) ay[ll] += t*ax[ll]; 859fd41dd0SBarry Smith } 869fd41dd0SBarry Smith } 879fd41dd0SBarry Smith ipvt[n] = n; 885f8bbccaSHong Zhang if (a[n + n * n] == 0.0) { 895f8bbccaSHong Zhang if (allowzeropivot) { 905f8bbccaSHong Zhang PetscErrorCode ierr; 915f8bbccaSHong Zhang ierr = PetscInfo1(NULL,"Zero pivot, row %D\n",n-1);CHKERRQ(ierr); 92*70d8d27cSBarry Smith if (zeropivotdetected) *zeropivotdetected = PETSC_TRUE; 935f8bbccaSHong Zhang } else SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_MAT_LU_ZRPVT,"Zero pivot, row %D",n-1); 945f8bbccaSHong Zhang } 953a40ed3dSBarry Smith PetscFunctionReturn(0); 969fd41dd0SBarry Smith } 979fd41dd0SBarry Smith 98