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) 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 /* Parameter adjustments */ 28 --ipvt; 29 a -= n + 1; 30 31 /* Function Body */ 32 nm1 = n - 1; 33 for (k = 1; k <= nm1; ++k) { 34 kp1 = k + 1; 35 kn = k*n; 36 knp1 = k*n + k; 37 38 /* find l = pivot index */ 39 40 i__2 = n - k + 1; 41 aa = &a[knp1]; 42 max = PetscAbsScalar(aa[0]); 43 l = 1; 44 for (ll=1; ll<i__2; ll++) { 45 tmp = PetscAbsScalar(aa[ll]); 46 if (tmp > max) { max = tmp; l = ll+1;} 47 } 48 l += k - 1; 49 ipvt[k] = l; 50 51 if (a[l + kn] == 0.0) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_MAT_LU_ZRPVT,"Zero pivot, row %D",k-1); 52 53 /* interchange if necessary */ 54 55 if (l != k) { 56 t = a[l + kn]; 57 a[l + kn] = a[knp1]; 58 a[knp1] = t; 59 } 60 61 /* compute multipliers */ 62 63 t = -1. / a[knp1]; 64 i__2 = n - k; 65 aa = &a[1 + knp1]; 66 for (ll=0; ll<i__2; ll++) aa[ll] *= t; 67 68 /* row elimination with column indexing */ 69 70 ax = aa; 71 for (j = kp1; j <= n; ++j) { 72 jn1 = j*n; 73 t = a[l + jn1]; 74 if (l != k) { 75 a[l + jn1] = a[k + jn1]; 76 a[k + jn1] = t; 77 } 78 79 i__3 = n - k; 80 ay = &a[1+k+jn1]; 81 for (ll=0; ll<i__3; ll++) ay[ll] += t*ax[ll]; 82 } 83 } 84 ipvt[n] = n; 85 if (a[n + n * n] == 0.0) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_MAT_LU_ZRPVT,"Zero pivot, row %D",n-1); 86 PetscFunctionReturn(0); 87 } 88 89