1be1d678aSKris Buschelman 2a97b7df5SSatish Balay /* 39fd41dd0SBarry Smith This routine was converted by f2c from Linpack source 49fd41dd0SBarry Smith linpack. this version dated 08/14/78 59fd41dd0SBarry Smith cleve moler, university of new mexico, argonne national lab. 659539b86SBarry Smith 759539b86SBarry Smith Does an LU factorization with partial pivoting of a dense 89d8b60e5SBarry Smith n by n matrix. 99d8b60e5SBarry Smith 109d8b60e5SBarry Smith Used by the sparse factorization routines in 11dd882469SBarry Smith src/mat/impls/baij/seq 1259539b86SBarry Smith 139fd41dd0SBarry Smith */ 14c6db04a5SJed Brown #include <petscsys.h> 159fd41dd0SBarry Smith 16db87b0f2SBarry Smith PETSC_INTERN PetscErrorCode PetscLINPACKgefa(MatScalar *a,PetscInt n,PetscInt *ipvt,PetscBool allowzeropivot,PetscBool *zeropivotdetected) 179fd41dd0SBarry Smith { 18690b6cddSBarry Smith PetscInt i__2,i__3,kp1,nm1,j,k,l,ll,kn,knp1,jn1; 193f1db9ecSBarry Smith MatScalar t,*ax,*ay,*aa; 20329f5518SBarry Smith MatReal tmp,max; 219fd41dd0SBarry Smith 223a40ed3dSBarry Smith PetscFunctionBegin; 235f8bbccaSHong Zhang if (zeropivotdetected) *zeropivotdetected = PETSC_FALSE; 245f8bbccaSHong Zhang 259fd41dd0SBarry Smith /* Parameter adjustments */ 269fd41dd0SBarry Smith --ipvt; 2739d66777SBarry Smith a -= n + 1; 289fd41dd0SBarry Smith 299fd41dd0SBarry Smith /* Function Body */ 309fd41dd0SBarry Smith nm1 = n - 1; 3139d66777SBarry Smith for (k = 1; k <= nm1; ++k) { 329fd41dd0SBarry Smith kp1 = k + 1; 3339d66777SBarry Smith kn = k*n; 3439d66777SBarry Smith knp1 = k*n + k; 359fd41dd0SBarry Smith 369fd41dd0SBarry Smith /* find l = pivot index */ 379fd41dd0SBarry Smith 389fd41dd0SBarry Smith i__2 = n - k + 1; 3939d66777SBarry Smith aa = &a[knp1]; 409fd41dd0SBarry Smith max = PetscAbsScalar(aa[0]); 419fd41dd0SBarry Smith l = 1; 429fd41dd0SBarry Smith for (ll=1; ll<i__2; ll++) { 439fd41dd0SBarry Smith tmp = PetscAbsScalar(aa[ll]); 449fd41dd0SBarry Smith if (tmp > max) { max = tmp; l = ll+1;} 459fd41dd0SBarry Smith } 469fd41dd0SBarry Smith l += k - 1; 479fd41dd0SBarry Smith ipvt[k] = l; 489fd41dd0SBarry Smith 495f8bbccaSHong Zhang if (a[l + kn] == 0.0) { 505f8bbccaSHong Zhang if (allowzeropivot) { 51*9566063dSJacob Faibussowitsch PetscCall(PetscInfo(NULL,"Zero pivot, row %" PetscInt_FMT "\n",k-1)); 5270d8d27cSBarry Smith if (zeropivotdetected) *zeropivotdetected = PETSC_TRUE; 5398921bdaSJacob Faibussowitsch } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_MAT_LU_ZRPVT,"Zero pivot, row %" PetscInt_FMT,k-1); 545f8bbccaSHong Zhang } 559fd41dd0SBarry Smith 569fd41dd0SBarry Smith /* interchange if necessary */ 579fd41dd0SBarry Smith if (l != k) { 5839d66777SBarry Smith t = a[l + kn]; 5939d66777SBarry Smith a[l + kn] = a[knp1]; 6039d66777SBarry Smith a[knp1] = t; 619fd41dd0SBarry Smith } 629fd41dd0SBarry Smith 639fd41dd0SBarry Smith /* compute multipliers */ 6439d66777SBarry Smith t = -1. / a[knp1]; 659fd41dd0SBarry Smith i__2 = n - k; 6639d66777SBarry Smith aa = &a[1 + knp1]; 6726fbe8dcSKarl Rupp for (ll=0; ll<i__2; ll++) aa[ll] *= t; 689fd41dd0SBarry Smith 699fd41dd0SBarry Smith /* row elimination with column indexing */ 7039d66777SBarry Smith ax = aa; 719fd41dd0SBarry Smith for (j = kp1; j <= n; ++j) { 728d3e6ddaSBarry Smith jn1 = j*n; 738d3e6ddaSBarry Smith t = a[l + jn1]; 749fd41dd0SBarry Smith if (l != k) { 758d3e6ddaSBarry Smith a[l + jn1] = a[k + jn1]; 768d3e6ddaSBarry Smith a[k + jn1] = t; 779fd41dd0SBarry Smith } 789fd41dd0SBarry Smith 799fd41dd0SBarry Smith i__3 = n - k; 808d3e6ddaSBarry Smith ay = &a[1+k+jn1]; 8126fbe8dcSKarl Rupp for (ll=0; ll<i__3; ll++) ay[ll] += t*ax[ll]; 829fd41dd0SBarry Smith } 839fd41dd0SBarry Smith } 849fd41dd0SBarry Smith ipvt[n] = n; 855f8bbccaSHong Zhang if (a[n + n * n] == 0.0) { 865f8bbccaSHong Zhang if (allowzeropivot) { 87*9566063dSJacob Faibussowitsch PetscCall(PetscInfo(NULL,"Zero pivot, row %" PetscInt_FMT "\n",n-1)); 8870d8d27cSBarry Smith if (zeropivotdetected) *zeropivotdetected = PETSC_TRUE; 8998921bdaSJacob Faibussowitsch } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_MAT_LU_ZRPVT,"Zero pivot, row %" PetscInt_FMT,n-1); 905f8bbccaSHong Zhang } 913a40ed3dSBarry Smith PetscFunctionReturn(0); 929fd41dd0SBarry Smith } 93