C
C  This file is part of MUMPS 5.9.0, released
C  on Tue Apr 28 13:05:59 UTC 2026
C
C
C  Copyright 1991-2026 CERFACS, CNRS, ENS Lyon, INP Toulouse, Inria,
C  Mumps Technologies, University of Bordeaux.
C
C  This version of MUMPS is provided to you free of charge. It is
C  released under the CeCILL-C license 
C  (see doc/CeCILL-C_V1-en.txt, doc/CeCILL-C_V1-fr.txt, and
C  https://cecill.info/licences/Licence_CeCILL-C_V1-en.html)
C
      SUBROUTINE SMUMPS_FACTO_ROOT( 
     &           MPA, MYID, MASTER_OF_ROOT,
     &           root, roota, N, IROOT,
     &           COMM, IW, LIW, IFREE,
     &           A, LA, PTRAST, PTLUST_S, PTRFAC,
     &           STEP, INFO, LDLT, QR,
     &           WK, LWK, KEEP,KEEP8,DKEEP,OPELIW,
     &           DET_EXP, DET_MANT, DET_SIGN
     & )
        USE MUMPS_LR_STATS, ONLY: UPD_FLOP_ROOT
        USE MUMPS_INTR_TYPES, ONLY : MUMPS_ROOT_STRUC
        USE SMUMPS_INTR_TYPES, ONLY : SMUMPS_ROOT_STRUC
         IMPLICIT NONE
      INCLUDE 'mpif.h'
      TYPE ( MUMPS_ROOT_STRUC ) :: root
      TYPE ( SMUMPS_ROOT_STRUC ) :: roota
      INTEGER, INTENT(IN) :: MPA
      INTEGER N, IROOT, COMM, LIW, MYID, IFREE, MASTER_OF_ROOT
      INTEGER(8) :: LA
      INTEGER(8) :: LWK
      REAL WK( LWK )
      INTEGER KEEP(500)
      REAL    DKEEP(230)
      INTEGER(8) KEEP8(150)
      INTEGER(8) :: PTRAST(KEEP(28))
      INTEGER(8) :: PTRFAC(KEEP(28))
      INTEGER PTLUST_S(KEEP(28)), STEP(N), IW( LIW )
      INTEGER INFO( 2 ), LDLT, QR
      REAL A( LA )
      DOUBLE PRECISION, intent(inout) :: OPELIW
      INTEGER, INTENT(INOUT) :: DET_SIGN, DET_EXP
      REAL, INTENT(INOUT) :: DET_MANT
#if ! defined(NOSCALAPACK)
      INTEGER IOLDPS
      INTEGER(8) :: IAPOS
      INTEGER LOCAL_M, LOCAL_N, LPIV, IERR 
      DOUBLE PRECISION :: FLOPS_ROOT
      INTEGER(8) :: ENTRIES_ROOT
      INTEGER allocok
      INTEGER FWD_LOCAL_N_RHS, FWD_MTYPE 
#endif
      INCLUDE 'mumps_headers.h'
      INTEGER, EXTERNAL :: MUMPS_NUMROC
        IF ( .NOT. root%yes ) RETURN
        IF ( KEEP(60) .NE. 0 ) THEN
          IF ((LDLT == 1 .OR. LDLT == 2) .AND. KEEP(60) == 3 ) THEN
            CALL SMUMPS_SYMMETRIZE( WK, root%MBLOCK,
     &      root%MYROW, root%MYCOL, root%NPROW, root%NPCOL,
     &      roota%SCHUR_POINTER(1),
     &      root%SCHUR_LLD, root%SCHUR_NLOC,
     &      root%TOT_ROOT_SIZE, MYID, COMM )
          ENDIF
        RETURN
        ENDIF
#if ! defined(NOSCALAPACK)
        IF (MPA.GT.0) THEN
         IF (MYID.EQ.MASTER_OF_ROOT) THEN
           CALL  MUMPS_GET_FLOPS_COST
     &     (root%TOT_ROOT_SIZE, root%TOT_ROOT_SIZE, root%TOT_ROOT_SIZE,
     &      LDLT, 3, FLOPS_ROOT)
           WRITE(MPA,'(A, A, 1PD10.3)')
     &     " ... Start processing the root node with ScaLAPACK, ", 
     &     " remaining flops                = ", FLOPS_ROOT
         ENDIF
        ENDIF
        IOLDPS  = PTLUST_S(STEP(IROOT))+KEEP(IXSZ)
        IAPOS   = PTRAST(STEP(IROOT))
        LOCAL_M = IW( IOLDPS + 2 )
        LOCAL_N = IW( IOLDPS + 1 )
        IAPOS = PTRFAC(IW ( IOLDPS + 4 ))
        IF ( LDLT.EQ.0 .OR. LDLT.EQ.2 .OR. QR.ne.0 ) THEN
         LPIV = LOCAL_M + root%MBLOCK
        ELSE
         LPIV = 1
        END IF
        IF (associated( root%IPIV )) DEALLOCATE(root%IPIV)
        root%LPIV = LPIV
        ALLOCATE( root%IPIV( LPIV ), stat = allocok )
        IF ( allocok .GT. 0 ) THEN
          INFO(1) = -13
          INFO(2) = LPIV
          WRITE(*,*) MYID,': problem allocating IPIV(',LPIV,') in root'
          CALL MUMPS_ABORT()
        END IF
        CALL DESCINIT( root%DESCRIPTOR(1), root%TOT_ROOT_SIZE,
     &      root%TOT_ROOT_SIZE, root%MBLOCK, root%NBLOCK,
     &      0, 0, root%CNTXT_BLACS, LOCAL_M, IERR )
        IF ( LDLT.EQ.2 ) THEN
           IF(root%MBLOCK.NE.root%NBLOCK) THEN
              WRITE(*,*) ' Error: symmetrization only works for'
              WRITE(*,*) ' square block sizes, MBLOCK/NBLOCK=',
     &        root%MBLOCK, root%NBLOCK
              CALL MUMPS_ABORT()
            END IF
            IF ( LWK .LT. min(
     &           int(root%MBLOCK,8) * int(root%NBLOCK,8),
     &           int(root%TOT_ROOT_SIZE,8)* int(root%TOT_ROOT_SIZE,8 )
     &           )) THEN
               WRITE(*,*) 'Not enough workspace for symmetrization.'
               CALL MUMPS_ABORT()
            END IF
            CALL SMUMPS_SYMMETRIZE( WK, root%MBLOCK,
     &      root%MYROW, root%MYCOL, root%NPROW, root%NPCOL,
     &      A( IAPOS ), LOCAL_M, LOCAL_N,
     &      root%TOT_ROOT_SIZE, MYID, COMM )
        END IF
        IF (LDLT.EQ.0.OR.LDLT.EQ.2) THEN
          CALL psgetrf( root%TOT_ROOT_SIZE, root%TOT_ROOT_SIZE,
     &      A( IAPOS ),
     &      1, 1, root%DESCRIPTOR(1), root%IPIV(1), IERR )
          IF ( IERR .GT. 0 ) THEN
              INFO(1)=-10
              INFO(2)=IERR-1
          END IF
        ELSE
          CALL pspotrf('L',root%TOT_ROOT_SIZE,A(IAPOS),
     &      1,1,root%DESCRIPTOR(1),IERR)
            IF ( IERR .GT. 0 ) THEN
              INFO(1)=-40
              INFO(2)=IERR-1
            END IF
        END IF
        IF (IERR .GT. 0) THEN
          CALL MUMPS_UPDATE_FLOPS_ROOT( OPELIW, LDLT,
     &                          root%TOT_ROOT_SIZE, INFO(2),
     &                          root%NPROW, root%NPCOL, MYID )
          IF (KEEP(486) .GT. 0) THEN
            CALL UPD_FLOP_ROOT( LDLT,
     &                          root%TOT_ROOT_SIZE, INFO(2),
     &                          root%NPROW, root%NPCOL, MYID )
          ENDIF
        ELSE
          CALL MUMPS_UPDATE_FLOPS_ROOT( OPELIW, LDLT,
     &                          root%TOT_ROOT_SIZE, root%TOT_ROOT_SIZE,
     &                          root%NPROW, root%NPCOL, MYID )
          IF (KEEP(486) .GT. 0) THEN
            CALL UPD_FLOP_ROOT( LDLT,
     &                          root%TOT_ROOT_SIZE, root%TOT_ROOT_SIZE,
     &                          root%NPROW, root%NPCOL, MYID )
          ENDIF
        ENDIF
        IF ( LDLT .EQ. 0 ) THEN
          ENTRIES_ROOT = int(root%TOT_ROOT_SIZE,8)
     &                 * int(root%TOT_ROOT_SIZE,8)
        ELSE
          ENTRIES_ROOT = int(root%TOT_ROOT_SIZE,8)
     &                 * int(root%TOT_ROOT_SIZE+1,8)/2_8
        ENDIF
        KEEP8(10)=KEEP8(10) + ENTRIES_ROOT /
     &                        int(root%NPROW * root%NPCOL,8)
        IF (MYID .eq. MASTER_OF_ROOT) THEN
          KEEP8(10)=KEEP8(10) +
     &    mod(ENTRIES_ROOT, int(root%NPROW*root%NPCOL,8))
        ENDIF
        CALL SMUMPS_PAR_ROOT_MINMAX_PIV_UPD (
     &         root%MBLOCK, root%IPIV(1),root%MYROW,
     &         root%MYCOL, root%NPROW, root%NPCOL, A(IAPOS), LOCAL_M,
     &         LOCAL_N, root%TOT_ROOT_SIZE, MYID, DKEEP, KEEP, LDLT)
        IF (KEEP(258).NE.0) THEN
           IF (root%MBLOCK.NE.root%NBLOCK) THEN
            write(*,*) "Internal error in SMUMPS_FACTO_ROOT:",
     &      "Block size different for rows and columns",
     &      root%MBLOCK, root%NBLOCK
            CALL MUMPS_ABORT()
          ENDIF
          CALL SMUMPS_GETDETER2D(root%MBLOCK, root%IPIV(1),root%MYROW,
     &         root%MYCOL, root%NPROW, root%NPCOL, A(IAPOS), LOCAL_M,
     &         LOCAL_N, root%TOT_ROOT_SIZE, MYID, DET_MANT, DET_EXP,
     &         LDLT)
        ENDIF
        IF (KEEP(252) .NE. 0) THEN
          FWD_LOCAL_N_RHS = MUMPS_NUMROC(KEEP(253), root%NBLOCK,
     &                      root%MYCOL, 0, root%NPCOL)
          FWD_LOCAL_N_RHS = max(1,FWD_LOCAL_N_RHS)
          FWD_MTYPE       = 1 
          CALL SMUMPS_SOLVE_2D_BCYCLIC(
     &         root%TOT_ROOT_SIZE,
     &         KEEP(253),          
     &         FWD_MTYPE,
     &         A(IAPOS),
     &         root%DESCRIPTOR(1),
     &         LOCAL_M, LOCAL_N, FWD_LOCAL_N_RHS,
     &         root%IPIV(1), LPIV,
     &         roota%RHS_ROOT(1,1), LDLT,
     &         root%MBLOCK, root%NBLOCK,
     &         root%CNTXT_BLACS, IERR)
        ENDIF
#endif
      RETURN
      END SUBROUTINE SMUMPS_FACTO_ROOT
