1be1d678aSKris Buschelman #define PETSCMAT_DLL 2be1d678aSKris Buschelman 3a97b7df5SSatish Balay /* 49fd41dd0SBarry Smith This routine was converted by f2c from Linpack source 59fd41dd0SBarry Smith linpack. this version dated 08/14/78 69fd41dd0SBarry Smith cleve moler, university of new mexico, argonne national lab. 759539b86SBarry Smith 859539b86SBarry Smith Does an LU factorization with partial pivoting of a dense 99d8b60e5SBarry Smith n by n matrix. 109d8b60e5SBarry Smith 119d8b60e5SBarry Smith Used by the sparse factorization routines in 12dd882469SBarry Smith src/mat/impls/baij/seq 1359539b86SBarry Smith 149fd41dd0SBarry Smith */ 15d382aafbSBarry Smith #include "petscsys.h" 169fd41dd0SBarry Smith 174a2ae208SSatish Balay #undef __FUNCT__ 184a2ae208SSatish Balay #define __FUNCT__ "LINPACKdgefa" 19690b6cddSBarry Smith PetscErrorCode LINPACKdgefa(MatScalar *a,PetscInt n,PetscInt *ipvt) 209fd41dd0SBarry Smith { 21690b6cddSBarry Smith PetscInt i__2,i__3,kp1,nm1,j,k,l,ll,kn,knp1,jn1; 223f1db9ecSBarry Smith MatScalar t,*ax,*ay,*aa; 23329f5518SBarry Smith MatReal tmp,max; 249fd41dd0SBarry Smith 259fd41dd0SBarry Smith /* gaussian elimination with partial pivoting */ 269fd41dd0SBarry Smith 273a40ed3dSBarry Smith PetscFunctionBegin; 289fd41dd0SBarry Smith /* Parameter adjustments */ 299fd41dd0SBarry Smith --ipvt; 3039d66777SBarry Smith a -= n + 1; 319fd41dd0SBarry Smith 329fd41dd0SBarry Smith /* Function Body */ 339fd41dd0SBarry Smith nm1 = n - 1; 3439d66777SBarry Smith for (k = 1; k <= nm1; ++k) { 359fd41dd0SBarry Smith kp1 = k + 1; 3639d66777SBarry Smith kn = k*n; 3739d66777SBarry Smith knp1 = k*n + k; 389fd41dd0SBarry Smith 399fd41dd0SBarry Smith /* find l = pivot index */ 409fd41dd0SBarry Smith 419fd41dd0SBarry Smith i__2 = n - k + 1; 4239d66777SBarry Smith aa = &a[knp1]; 439fd41dd0SBarry Smith max = PetscAbsScalar(aa[0]); 449fd41dd0SBarry Smith l = 1; 459fd41dd0SBarry Smith for (ll=1; ll<i__2; ll++) { 469fd41dd0SBarry Smith tmp = PetscAbsScalar(aa[ll]); 479fd41dd0SBarry Smith if (tmp > max) { max = tmp; l = ll+1;} 489fd41dd0SBarry Smith } 499fd41dd0SBarry Smith l += k - 1; 509fd41dd0SBarry Smith ipvt[k] = l; 519fd41dd0SBarry Smith 52*65e19b50SBarry Smith if (a[l + kn] == 0.0) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_MAT_LU_ZRPVT,"Zero pivot, row %D",k-1); 539fd41dd0SBarry Smith 549fd41dd0SBarry Smith /* interchange if necessary */ 559fd41dd0SBarry Smith 569fd41dd0SBarry Smith if (l != k) { 5739d66777SBarry Smith t = a[l + kn]; 5839d66777SBarry Smith a[l + kn] = a[knp1]; 5939d66777SBarry Smith a[knp1] = t; 609fd41dd0SBarry Smith } 619fd41dd0SBarry Smith 629fd41dd0SBarry Smith /* compute multipliers */ 639fd41dd0SBarry Smith 6439d66777SBarry Smith t = -1. / a[knp1]; 659fd41dd0SBarry Smith i__2 = n - k; 6639d66777SBarry Smith aa = &a[1 + knp1]; 679fd41dd0SBarry Smith for (ll=0; ll<i__2; ll++) { 689fd41dd0SBarry Smith aa[ll] *= t; 699fd41dd0SBarry Smith } 709fd41dd0SBarry Smith 719fd41dd0SBarry Smith /* row elimination with column indexing */ 729fd41dd0SBarry Smith 7339d66777SBarry Smith ax = aa; 749fd41dd0SBarry Smith for (j = kp1; j <= n; ++j) { 758d3e6ddaSBarry Smith jn1 = j*n; 768d3e6ddaSBarry Smith t = a[l + jn1]; 779fd41dd0SBarry Smith if (l != k) { 788d3e6ddaSBarry Smith a[l + jn1] = a[k + jn1]; 798d3e6ddaSBarry Smith a[k + jn1] = t; 809fd41dd0SBarry Smith } 819fd41dd0SBarry Smith 829fd41dd0SBarry Smith i__3 = n - k; 838d3e6ddaSBarry Smith ay = &a[1+k+jn1]; 849fd41dd0SBarry Smith for (ll=0; ll<i__3; ll++) { 859fd41dd0SBarry Smith ay[ll] += t*ax[ll]; 869fd41dd0SBarry Smith } 879fd41dd0SBarry Smith } 889fd41dd0SBarry Smith } 899fd41dd0SBarry Smith ipvt[n] = n; 90*65e19b50SBarry Smith if (a[n + n * n] == 0.0) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_MAT_LU_ZRPVT,"Zero pivot, row %D",n-1); 913a40ed3dSBarry Smith PetscFunctionReturn(0); 929fd41dd0SBarry Smith } 939fd41dd0SBarry Smith 94