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 PETSC_INTERN PetscErrorCode PetscLINPACKgefa(MatScalar *a,PetscInt n,PetscInt *ipvt,PetscBool allowzeropivot,PetscBool *zeropivotdetected) 17 { 18 PetscInt i__2,i__3,kp1,nm1,j,k,l,ll,kn,knp1,jn1; 19 MatScalar t,*ax,*ay,*aa; 20 MatReal tmp,max; 21 22 PetscFunctionBegin; 23 if (zeropivotdetected) *zeropivotdetected = PETSC_FALSE; 24 25 /* Parameter adjustments */ 26 --ipvt; 27 a -= n + 1; 28 29 /* Function Body */ 30 nm1 = n - 1; 31 for (k = 1; k <= nm1; ++k) { 32 kp1 = k + 1; 33 kn = k*n; 34 knp1 = k*n + k; 35 36 /* find l = pivot index */ 37 38 i__2 = n - k + 1; 39 aa = &a[knp1]; 40 max = PetscAbsScalar(aa[0]); 41 l = 1; 42 for (ll=1; ll<i__2; ll++) { 43 tmp = PetscAbsScalar(aa[ll]); 44 if (tmp > max) { max = tmp; l = ll+1;} 45 } 46 l += k - 1; 47 ipvt[k] = l; 48 49 if (a[l + kn] == 0.0) { 50 if (allowzeropivot) { 51 PetscErrorCode ierr; 52 ierr = PetscInfo1(NULL,"Zero pivot, row %D\n",k-1);CHKERRQ(ierr); 53 if (zeropivotdetected) *zeropivotdetected = PETSC_TRUE; 54 } else SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_MAT_LU_ZRPVT,"Zero pivot, row %D",k-1); 55 } 56 57 /* interchange if necessary */ 58 if (l != k) { 59 t = a[l + kn]; 60 a[l + kn] = a[knp1]; 61 a[knp1] = t; 62 } 63 64 /* compute multipliers */ 65 t = -1. / a[knp1]; 66 i__2 = n - k; 67 aa = &a[1 + knp1]; 68 for (ll=0; ll<i__2; ll++) aa[ll] *= t; 69 70 /* row elimination with column indexing */ 71 ax = aa; 72 for (j = kp1; j <= n; ++j) { 73 jn1 = j*n; 74 t = a[l + jn1]; 75 if (l != k) { 76 a[l + jn1] = a[k + jn1]; 77 a[k + jn1] = t; 78 } 79 80 i__3 = n - k; 81 ay = &a[1+k+jn1]; 82 for (ll=0; ll<i__3; ll++) ay[ll] += t*ax[ll]; 83 } 84 } 85 ipvt[n] = n; 86 if (a[n + n * n] == 0.0) { 87 if (allowzeropivot) { 88 PetscErrorCode ierr; 89 ierr = PetscInfo1(NULL,"Zero pivot, row %D\n",n-1);CHKERRQ(ierr); 90 if (zeropivotdetected) *zeropivotdetected = PETSC_TRUE; 91 } else SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_MAT_LU_ZRPVT,"Zero pivot, row %D",n-1); 92 } 93 PetscFunctionReturn(0); 94 } 95 96