1 2 /* 3 This routine was converted by f2c from Linpack source 4 linpack. this version dated 08/14/78 5 cleve moler, university of new mexico, argonne national lab. 6 7 Does an LU factorization with partial pivoting of a dense 8 n by n matrix. 9 10 Used by the sparse factorization routines in 11 src/mat/impls/baij/seq 12 13 */ 14 #include <petscsys.h> 15 16 #undef __FUNCT__ 17 #define __FUNCT__ "PetscLINPACKgefa" 18 PetscErrorCode PetscLINPACKgefa(MatScalar *a,PetscInt n,PetscInt *ipvt,PetscBool allowzeropivot,PetscBool *zeropivotdetected) 19 { 20 PetscInt i__2,i__3,kp1,nm1,j,k,l,ll,kn,knp1,jn1; 21 MatScalar t,*ax,*ay,*aa; 22 MatReal tmp,max; 23 24 /* gaussian elimination with partial pivoting */ 25 26 PetscFunctionBegin; 27 if (zeropivotdetected) *zeropivotdetected = PETSC_FALSE; 28 29 /* Parameter adjustments */ 30 --ipvt; 31 a -= n + 1; 32 33 /* Function Body */ 34 nm1 = n - 1; 35 for (k = 1; k <= nm1; ++k) { 36 kp1 = k + 1; 37 kn = k*n; 38 knp1 = k*n + k; 39 40 /* find l = pivot index */ 41 42 i__2 = n - k + 1; 43 aa = &a[knp1]; 44 max = PetscAbsScalar(aa[0]); 45 l = 1; 46 for (ll=1; ll<i__2; ll++) { 47 tmp = PetscAbsScalar(aa[ll]); 48 if (tmp > max) { max = tmp; l = ll+1;} 49 } 50 l += k - 1; 51 ipvt[k] = l; 52 53 if (a[l + kn] == 0.0) { 54 if (allowzeropivot) { 55 PetscErrorCode ierr; 56 ierr = PetscInfo1(NULL,"Zero pivot, row %D\n",k-1);CHKERRQ(ierr); 57 *zeropivotdetected = PETSC_TRUE; 58 } else SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_MAT_LU_ZRPVT,"Zero pivot, row %D",k-1); 59 } 60 61 /* interchange if necessary */ 62 if (l != k) { 63 t = a[l + kn]; 64 a[l + kn] = a[knp1]; 65 a[knp1] = t; 66 } 67 68 /* compute multipliers */ 69 t = -1. / a[knp1]; 70 i__2 = n - k; 71 aa = &a[1 + knp1]; 72 for (ll=0; ll<i__2; ll++) aa[ll] *= t; 73 74 /* row elimination with column indexing */ 75 ax = aa; 76 for (j = kp1; j <= n; ++j) { 77 jn1 = j*n; 78 t = a[l + jn1]; 79 if (l != k) { 80 a[l + jn1] = a[k + jn1]; 81 a[k + jn1] = t; 82 } 83 84 i__3 = n - k; 85 ay = &a[1+k+jn1]; 86 for (ll=0; ll<i__3; ll++) ay[ll] += t*ax[ll]; 87 } 88 } 89 ipvt[n] = n; 90 if (a[n + n * n] == 0.0) { 91 if (allowzeropivot) { 92 PetscErrorCode ierr; 93 ierr = PetscInfo1(NULL,"Zero pivot, row %D\n",n-1);CHKERRQ(ierr); 94 *zeropivotdetected = PETSC_TRUE; 95 } else SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_MAT_LU_ZRPVT,"Zero pivot, row %D",n-1); 96 } 97 PetscFunctionReturn(0); 98 } 99 100