1*be1d678aSKris Buschelman #define PETSCMAT_DLL 2*be1d678aSKris 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 1259539b86SBarry Smith src/mat/impls/baij/seq and src/mat/impls/bdiag/seq 1359539b86SBarry Smith 1471c5468dSBarry Smith See also src/inline/ilu.h 159fd41dd0SBarry Smith */ 169fd41dd0SBarry Smith #include "petsc.h" 179fd41dd0SBarry Smith 184a2ae208SSatish Balay #undef __FUNCT__ 194a2ae208SSatish Balay #define __FUNCT__ "LINPACKdgefa" 20690b6cddSBarry Smith PetscErrorCode LINPACKdgefa(MatScalar *a,PetscInt n,PetscInt *ipvt) 219fd41dd0SBarry Smith { 22690b6cddSBarry Smith PetscInt i__2,i__3,kp1,nm1,j,k,l,ll,kn,knp1,jn1; 233f1db9ecSBarry Smith MatScalar t,*ax,*ay,*aa; 24329f5518SBarry Smith MatReal tmp,max; 259fd41dd0SBarry Smith 269fd41dd0SBarry Smith /* gaussian elimination with partial pivoting */ 279fd41dd0SBarry Smith 283a40ed3dSBarry Smith PetscFunctionBegin; 299fd41dd0SBarry Smith /* Parameter adjustments */ 309fd41dd0SBarry Smith --ipvt; 3139d66777SBarry Smith a -= n + 1; 329fd41dd0SBarry Smith 339fd41dd0SBarry Smith /* Function Body */ 349fd41dd0SBarry Smith nm1 = n - 1; 3539d66777SBarry Smith for (k = 1; k <= nm1; ++k) { 369fd41dd0SBarry Smith kp1 = k + 1; 3739d66777SBarry Smith kn = k*n; 3839d66777SBarry Smith knp1 = k*n + k; 399fd41dd0SBarry Smith 409fd41dd0SBarry Smith /* find l = pivot index */ 419fd41dd0SBarry Smith 429fd41dd0SBarry Smith i__2 = n - k + 1; 4339d66777SBarry Smith aa = &a[knp1]; 449fd41dd0SBarry Smith max = PetscAbsScalar(aa[0]); 459fd41dd0SBarry Smith l = 1; 469fd41dd0SBarry Smith for (ll=1; ll<i__2; ll++) { 479fd41dd0SBarry Smith tmp = PetscAbsScalar(aa[ll]); 489fd41dd0SBarry Smith if (tmp > max) { max = tmp; l = ll+1;} 499fd41dd0SBarry Smith } 509fd41dd0SBarry Smith l += k - 1; 519fd41dd0SBarry Smith ipvt[k] = l; 529fd41dd0SBarry Smith 535b8514ebSBarry Smith if (a[l + kn] == 0.0) { 5477431f27SBarry Smith SETERRQ1(PETSC_ERR_MAT_LU_ZRPVT,"Zero pivot, row %D",k-1); 559fd41dd0SBarry Smith } 569fd41dd0SBarry Smith 579fd41dd0SBarry Smith /* interchange if necessary */ 589fd41dd0SBarry Smith 599fd41dd0SBarry Smith if (l != k) { 6039d66777SBarry Smith t = a[l + kn]; 6139d66777SBarry Smith a[l + kn] = a[knp1]; 6239d66777SBarry Smith a[knp1] = t; 639fd41dd0SBarry Smith } 649fd41dd0SBarry Smith 659fd41dd0SBarry Smith /* compute multipliers */ 669fd41dd0SBarry Smith 6739d66777SBarry Smith t = -1. / a[knp1]; 689fd41dd0SBarry Smith i__2 = n - k; 6939d66777SBarry Smith aa = &a[1 + knp1]; 709fd41dd0SBarry Smith for (ll=0; ll<i__2; ll++) { 719fd41dd0SBarry Smith aa[ll] *= t; 729fd41dd0SBarry Smith } 739fd41dd0SBarry Smith 749fd41dd0SBarry Smith /* row elimination with column indexing */ 759fd41dd0SBarry Smith 7639d66777SBarry Smith ax = aa; 779fd41dd0SBarry Smith for (j = kp1; j <= n; ++j) { 788d3e6ddaSBarry Smith jn1 = j*n; 798d3e6ddaSBarry Smith t = a[l + jn1]; 809fd41dd0SBarry Smith if (l != k) { 818d3e6ddaSBarry Smith a[l + jn1] = a[k + jn1]; 828d3e6ddaSBarry Smith a[k + jn1] = t; 839fd41dd0SBarry Smith } 849fd41dd0SBarry Smith 859fd41dd0SBarry Smith i__3 = n - k; 868d3e6ddaSBarry Smith ay = &a[1+k+jn1]; 879fd41dd0SBarry Smith for (ll=0; ll<i__3; ll++) { 889fd41dd0SBarry Smith ay[ll] += t*ax[ll]; 899fd41dd0SBarry Smith } 909fd41dd0SBarry Smith } 919fd41dd0SBarry Smith } 929fd41dd0SBarry Smith ipvt[n] = n; 935b8514ebSBarry Smith if (a[n + n * n] == 0.0) { 9477431f27SBarry Smith SETERRQ1(PETSC_ERR_MAT_LU_ZRPVT,"Zero pivot, row %D",n-1); 959fd41dd0SBarry Smith } 963a40ed3dSBarry Smith PetscFunctionReturn(0); 979fd41dd0SBarry Smith } 989fd41dd0SBarry Smith 99