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