C ITGA21    SOURCE    CB215821  16/04/21    21:17:18     8920
CCC
C **********************************************************************
CCC
      SUBROUTINE INTEGRA21 (XTRI,X,NDIMX,LAM,DDEFPL,NDIMS,
     .                    nmodel,tolrel,nitmax,nescri,ues,nnumer,
     .                    deltax,kerre,iiter)
      IMPLICIT INTEGER(I-N)

      integer ndims,nmodel,nitmax,nescri,nnumer,ndimx,ues,kdummy
      real*8    xtri(ndimx),x(ndimx),ddefpl(ndims),lam,tolrel
      integer i,j,iiter,kerre,npcon,npcap,kdu,ndimv
      real*8    dl,lres,siginv(3)
      real*8    auxr1,vtLUiw,auxmax1,auxmax2,deltax
      real*8    xres(8),dx(8),Amat(64),Gmat(64),vecn(8),vecm(8)

      kerre=0
      ndimv=2
      npcon=ndims+1
      npcap=ndims+2
      kdummy=nmodel
      if (nmodel.eq.22) kdummy=23
      do i=1,8
          xres(i)=0.D0
          dx(i)=0.D0
          vecn(i)=0.D0
          vecm(i)=0.D0
        enddo
      do i=1,64
          Amat(i)=0.D0
          Gmat(i)=0.D0
        enddo
      dl=1.D0
      iiter=-1
      call MatGenHookinv(Gmat,ndimx,ndims)
10    continue
      iiter=iiter+1
      kdu=0
      call yielddMAC(x,ndims,x(npcon),ndimv,lres,kdummy)
      call VecFlMAC(x,ndimx,vecm,nmodel)
      do i=1,ndimx
         xres(i)=lam*vecm(i)
         do j=1,ndimx
            xres(i)=xres(i)+Gmat((i-1)*ndimx+j)*(x(j)-xtri(j))
         enddo
      enddo
      auxmax1=ABS(dx(1))
      do i=2,ndims+1
         if (ABS(dx(i)).gt.auxmax1) auxmax1=ABS(dx(i))
      enddo
      auxmax2=ABS(x(1))
      do i=2,ndimx
         if (ABS(x(i)).gt.auxmax2) auxmax2=ABS(x(i))
      enddo
        auxr1=max(auxmax1,ABS(dl))/max(auxmax2,ABS(lam))
      if (iiter.eq.0) auxr1=1.D0
      if (nescri.eq.1) then
         call InvariantesPQT(x,ndims,siginv)
         write(ues,998)iiter,(siginv(i),i=1,3),x(ndimx-1),
     .                 x(ndimx),auxr1
998      format(I3,'Sig ',3(E10.4,1x),'V ',E10.4,1x,E10.4,' L ',E10.4)
      endif
      if ((auxr1.lt.tolrel).or.
     .   ((iiter.eq.nitmax).and.(auxr1.lt.sqrt(tolrel)))) then
c CONVERGIDO
         do i=1,ndims
            ddefpl(i)=0.D0
            do j=1,ndims
               ddefpl(i)=ddefpl(i)+Gmat((i-1)*ndimx+j)*(xtri(j)-x(j))
            enddo
         enddo
         return
      endif
c NO CONVERGIDO
      if (iiter.eq.nitmax) then
         kerre=1
         return
      endif
      call VecYiMAC(x,ndimx,vecn,nmodel)
      call HessMAC(x,ndimx,Amat,ndimx,nnumer,deltax,nmodel)
      do i=1,ndimx*ndimx
         Amat(i)=Gmat(i)+lam*Amat(i)
      enddo
      call DescLU(Amat,ndimx)
      dl=(lres-vtLUiw(vecn,Amat,xres,ndimx))
     .         /vtLUiw(vecn,Amat,vecm,ndimx)
      do i=1,ndimx
         xres(i)=-xres(i)-dl*vecm(i)
      enddo
      call LUiw(Amat,xres,dx,ndimx)
      lam=lam+dl
      do i=1,ndimx
         x(i)=x(i)+dx(i)
      enddo
      if (x(npcon).lt.0.D0) x(npcon)=0.D0
      if (x(npcap).lt.0.D0) x(npcap)=0.D0
      go to 10
      end