1*4431cf12SSatish Balay #ifndef lint 2*4431cf12SSatish Balay static char vcid[] = "$Id: dpause.c,v 1.7 1996/12/18 20:55:58 balay Exp $"; 3*4431cf12SSatish Balay #endif 49fd41dd0SBarry Smith /* 59fd41dd0SBarry Smith This routine was converted by f2c from Linpack source 69fd41dd0SBarry Smith linpack. this version dated 08/14/78 79fd41dd0SBarry Smith cleve moler, university of new mexico, argonne national lab. 89fd41dd0SBarry Smith */ 99fd41dd0SBarry Smith #include "petsc.h" 109fd41dd0SBarry Smith 11*4431cf12SSatish Balay #undef __FUNCTION__ 12*4431cf12SSatish Balay #define __FUNCTION__ "Linpack_DGEFA" 139fd41dd0SBarry Smith int Linpack_DGEFA(Scalar *a, int n, int *ipvt) 149fd41dd0SBarry Smith { 1539d66777SBarry Smith int i__2, i__3, kp1, nm1, j, k, l,ll,kn,knp1,jn; 166d84be18SBarry Smith Scalar t,*aa,*ax,*ay; 176d84be18SBarry Smith double tmp,max; 189fd41dd0SBarry Smith 199fd41dd0SBarry Smith /* gaussian elimination with partial pivoting */ 209fd41dd0SBarry Smith 219fd41dd0SBarry Smith /* Parameter adjustments */ 229fd41dd0SBarry Smith --ipvt; 2339d66777SBarry Smith a -= n + 1; 249fd41dd0SBarry Smith 259fd41dd0SBarry Smith /* Function Body */ 269fd41dd0SBarry Smith nm1 = n - 1; 2739d66777SBarry Smith for (k = 1; k <= nm1; ++k) { 289fd41dd0SBarry Smith kp1 = k + 1; 2939d66777SBarry Smith kn = k*n; 3039d66777SBarry Smith knp1 = k*n + k; 319fd41dd0SBarry Smith 329fd41dd0SBarry Smith /* find l = pivot index */ 339fd41dd0SBarry Smith 349fd41dd0SBarry Smith i__2 = n - k + 1; 3539d66777SBarry Smith aa = &a[knp1]; 369fd41dd0SBarry Smith max = PetscAbsScalar(aa[0]); 379fd41dd0SBarry Smith l = 1; 389fd41dd0SBarry Smith for ( ll=1; ll<i__2; ll++ ) { 399fd41dd0SBarry Smith tmp = PetscAbsScalar(aa[ll]); 409fd41dd0SBarry Smith if (tmp > max) { max = tmp; l = ll+1;} 419fd41dd0SBarry Smith } 429fd41dd0SBarry Smith l += k - 1; 439fd41dd0SBarry Smith ipvt[k] = l; 449fd41dd0SBarry Smith 4539d66777SBarry Smith if (a[l + kn] == 0.) { 469fd41dd0SBarry Smith SETERRQ(k,"Linpack_DGEFA:Zero pivot"); 479fd41dd0SBarry Smith } 489fd41dd0SBarry Smith 499fd41dd0SBarry Smith /* interchange if necessary */ 509fd41dd0SBarry Smith 519fd41dd0SBarry Smith if (l != k) { 5239d66777SBarry Smith t = a[l + kn]; 5339d66777SBarry Smith a[l + kn] = a[knp1]; 5439d66777SBarry Smith a[knp1] = t; 559fd41dd0SBarry Smith } 569fd41dd0SBarry Smith 579fd41dd0SBarry Smith /* compute multipliers */ 589fd41dd0SBarry Smith 5939d66777SBarry Smith t = -1. / a[knp1]; 609fd41dd0SBarry Smith i__2 = n - k; 6139d66777SBarry Smith aa = &a[1 + knp1]; 629fd41dd0SBarry Smith for ( ll=0; ll<i__2; ll++ ) { 639fd41dd0SBarry Smith aa[ll] *= t; 649fd41dd0SBarry Smith } 659fd41dd0SBarry Smith 669fd41dd0SBarry Smith /* row elimination with column indexing */ 679fd41dd0SBarry Smith 6839d66777SBarry Smith ax = aa; 699fd41dd0SBarry Smith for (j = kp1; j <= n; ++j) { 7039d66777SBarry Smith jn = j*n; 7139d66777SBarry Smith t = a[l + jn]; 729fd41dd0SBarry Smith if (l != k) { 7339d66777SBarry Smith a[l + jn] = a[k + jn]; 7439d66777SBarry Smith a[k + jn] = t; 759fd41dd0SBarry Smith } 769fd41dd0SBarry Smith 779fd41dd0SBarry Smith i__3 = n - k; 7839d66777SBarry Smith ay = &a[1+k+jn]; 799fd41dd0SBarry Smith for ( ll=0; ll<i__3; ll++ ) { 809fd41dd0SBarry Smith ay[ll] += t*ax[ll]; 819fd41dd0SBarry Smith } 829fd41dd0SBarry Smith } 839fd41dd0SBarry Smith } 849fd41dd0SBarry Smith ipvt[n] = n; 859fd41dd0SBarry Smith if (a[n + n * n] == 0.) { 869fd41dd0SBarry Smith SETERRQ(n,"Linpack_DGEFA:Zero pivot,final row"); 879fd41dd0SBarry Smith } 889fd41dd0SBarry Smith return 0; 899fd41dd0SBarry Smith } 909fd41dd0SBarry Smith 91