1 #ifdef PETSC_RCS_HEADER 2 static char vcid[] = "$Id: dgefa.c,v 1.12 1998/12/24 02:54:37 bsmith Exp bsmith $"; 3 #endif 4 /* 5 This routine was converted by f2c from Linpack source 6 linpack. this version dated 08/14/78 7 cleve moler, university of new mexico, argonne national lab. 8 9 Does an LU factorization with partial pivoting of a dense 10 n by n matrix. 11 12 Used by the sparse factorization routines in 13 src/mat/impls/baij/seq and src/mat/impls/bdiag/seq 14 15 */ 16 #include "petsc.h" 17 18 #undef __FUNC__ 19 #define __FUNC__ "Linpack_DGEFA" 20 int Linpack_DGEFA(MatScalar *a, int n, int *ipvt) 21 { 22 int i__2, i__3, kp1, nm1, j, k, l,ll,kn,knp1,jn1; 23 MatScalar t,*ax,*ay,*aa; 24 MatFloat tmp,max; 25 26 /* gaussian elimination with partial pivoting */ 27 28 PetscFunctionBegin; 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.) { 54 SETERRQ(k,0,"Zero pivot"); 55 } 56 57 /* interchange if necessary */ 58 59 if (l != k) { 60 t = a[l + kn]; 61 a[l + kn] = a[knp1]; 62 a[knp1] = t; 63 } 64 65 /* compute multipliers */ 66 67 t = -1. / a[knp1]; 68 i__2 = n - k; 69 aa = &a[1 + knp1]; 70 for ( ll=0; ll<i__2; ll++ ) { 71 aa[ll] *= t; 72 } 73 74 /* row elimination with column indexing */ 75 76 ax = aa; 77 for (j = kp1; j <= n; ++j) { 78 jn1 = j*n; 79 t = a[l + jn1]; 80 if (l != k) { 81 a[l + jn1] = a[k + jn1]; 82 a[k + jn1] = t; 83 } 84 85 i__3 = n - k; 86 ay = &a[1+k+jn1]; 87 for ( ll=0; ll<i__3; ll++ ) { 88 ay[ll] += t*ax[ll]; 89 } 90 } 91 } 92 ipvt[n] = n; 93 if (a[n + n * n] == 0.) { 94 SETERRQ(n,0,"Zero pivot,final row"); 95 } 96 PetscFunctionReturn(0); 97 } 98 99