subroutine pvCtensor(q1,q2,m1s,m2s,m3s,
     . FC0,FC1,FC2,FC3,FC4,FC5,FC6)
      implicit none
C     q1,q2 are the momenta in the propagators
C     m1s,m2s,m3s are the squares of the masses in the propagators
      include 'lib/TensorReduction/Include/types.f'
      include 'lib/TensorReduction/Include/TRconstants.f'
      include 'lib/TensorReduction/Include/pvCnames.f'
      include 'lib/TensorReduction/Include/pvCv.f'
      include 'lib/TensorReduction/Include/TRydef.f'
      include 'lib/TensorReduction/Include/TRmaxindex.f'
      include 'lib/TensorReduction/Include/pvRespectmaxcindex.f'
      include 'lib/TensorReduction/Include/pvrecurflags.f'
      include 'lib/TensorReduction/Include/TRbadpoint.f'
      include 'lib/TensorReduction/Include/pvforcerecalc.f'
      include 'lib/TensorReduction/Include/pvverbose.f'
      include 'lib/TensorReduction/Include/pvCitry.f'
      include 'lib/TensorReduction/Include/TRmetric.f'
      complex(dp):: FC0(-2:0),FC1(y1max,-2:0),FC2(y2max,-2:0),
     . FC3(y3max,-2:0),FC4(y4max,-2:0),FC5(y5max,-2:0),FC6(y6max,-2:0),
     . FC7(y7max,-2:0)
      real(dp):: p1Dp1,p2Dp2,p3Dp3,q1(4),q2(4)
      real(dp):: m1s,m2s,m3s,
     . pvSPK,
     . pvSPKK,pvSDDP,
     . pvSPKKK,pvSPPKK,
     . pvSDDPP,pvSDDPK,pvSDDDD,
     . pvSDDDDP,pvSDDPPP,pvSDDPPK,pvSPPPKK,pvSPPPPK,
     . pvSDDDDDD,pvSDDDDPP,pvSDDDDPK,pvSDDPPPP,pvSDDPPPK,pvSDDPPKK,
     . pvSDDPKKK,pvSPPPPPK,pvSPPPPKK,pvSPPPKKK
      real(dp)::q1save(4),q2save(4)
      integer:: n1,n2,n3,n4,n5,n6,n7,ep,C0i,pvCcache,itry
      logical:: failed
      common/q12save/q1save,q2save
      logical,save:: first=.true.
!$omp threadprivate(first,/q12save/)

c--- value of itry specifies which calculation to use for tensor coefficients:
c---    itry=0            regular PV recursion
c---    itry=1            small G recursion
c---    itry=2            small G and small Y recursion

      itry=0      ! Regular PV recursion is the default
      doGsing =.false.
      doGYsing=.false.
      doPsing =.false.
      doPFsing=.false.
      
      if (first) then
      first=.false.
      call pvarraysetup
      endif
      
      pvrespectmaxcindex=.true.

      q1save(:)=q1(:)
      q2save(:)=q2(:)

c      p1(nu)=q1(nu)
c      p2(nu)=q2(nu)-q1(nu)

      p1Dp1=q1(4)**2-q1(1)**2-q1(2)**2-q1(3)**2
      p3Dp3=q2(4)**2-q2(1)**2-q2(2)**2-q2(3)**2
      p2Dp2=p1Dp1+p3Dp3
     . -two*(q1(4)*q2(4)-q1(1)*q2(1)-q1(2)*q2(2)-q1(3)*q2(3))

c--- point from which to continue
   11 continue

      pvforcerecalc=.false.
      if     (itry .eq. 1) then
        doGsing=.true.
        pvforcerecalc=.true.
      elseif (itry .eq. 2) then
        doGsing=.false.
        doGYsing=.true.
        pvforcerecalc=.true.
      elseif (itry .eq. 3) then
c--- cannot compute point: set flag
        pvbadpoint=.true.   
      if (pvverbose) write(6,*) 'flag: badpoint  set in pvCtensor'
      return  
      endif
      
      C0i=pvCcache(p1Dp1,p2Dp2,p3Dp3,m1s,m2s,m3s)
c      write(6,*) 'C cache for ',p1Dp1,p2Dp2,p3Dp3,m1s,m2s,m3s
c      do n1=1,Ncc
c      write(6,'(i4,2f28.16)') n1,Cv(C0i+n1,0)
c      enddo
c      write(6,*)
      
      do ep=-2,0
      FC0(ep)=Cv(C0i+cc0,ep)
      enddo

      do ep=-2,0
      do n1=1,4
      FC1(n1,ep)=+Cv(C0i+cc1,ep)*q1(n1)+Cv(C0i+cc2,ep)*q2(n1)
      enddo
      enddo
    
 
      do ep=-2,0
      do n1=1,4
      do n2=n1,4
      FC2(y2(n1,n2),ep)=
     . +q1(n1)*q1(n2)*Cv(C0i+cc11,ep)
     . +q2(n1)*q2(n2)*Cv(C0i+cc22,ep)
     . +pvSPK(n1,n2,q1,q2)*Cv(C0i+cc12,ep)
     . +g(n1,n2)*Cv(C0i+cc00,ep)
      enddo
      enddo
      enddo

      if ((maxcindex .eq. 2) .and. (pvRespectmaxcindex)) then
        if (pvCitry(C0i) .eq. -1) then
        call pvCcheck(2,q1,q2,m1s,m2s,m3s,
     &   FC0,FC1,FC2,FC3,FC4,FC5,FC6,failed)
      if (failed) then
c          write(6,*) 'recursion in pvCtensor'
        itry=itry+1
        goto 11
      endif
      pvCitry(C0i)=itry
c        if (itry .gt. 0) then
c        write(6,*) 'pvCtensor success: itry=',itry
c        endif
        endif
        return
      endif

      do ep=-2,0
      do n1=1,4
      do n2=n1,4
      do n3=n2,4
      FC3(y3(n1,n2,n3),ep)=
     . +q1(n1)*q1(n2)*q1(n3)*Cv(C0i+cc111,ep)
     . +q2(n1)*q2(n2)*q2(n3)*Cv(C0i+cc222,ep)
     . +pvSPKK(n1,n2,n3,q2,q1)*Cv(C0i+cc112,ep)
     . +pvSPKK(n1,n2,n3,q1,q2)*Cv(C0i+cc122,ep)
     . +pvSDDP(n1,n2,n3,q1)*Cv(C0i+cc001,ep)
     . +pvSDDP(n1,n2,n3,q2)*Cv(C0i+cc002,ep)
      enddo
      enddo
      enddo
      enddo

c--- This code can be used to check that the calculated tensor (e.g.
c---  by one of the recursion methods) satisfies the usual PV relations
c      call PVchecktri(q1,q2,m1s,m2s,m3s,FC0,FC1,FC2,FC3,FC4,FC5,FC6,failed)
c---

      if ((maxcindex .eq. 3) .and. (pvRespectmaxcindex)) then
        call pvCcheck(3,q1,q2,m1s,m2s,m3s,
     &   FC0,FC1,FC2,FC3,FC4,FC5,FC6,failed)
      if (failed) then
c        write(6,*) 'recursion in pvCtensor'
        itry=itry+1
        goto 11
      endif
        return
      endif

      do ep=-2,0
      do n1=1,4
      do n2=n1,4
      do n3=n2,4
      do n4=n3,4
      FC4(y4(n1,n2,n3,n4),ep)=
     . +q1(n1)*q1(n2)*q1(n3)*q1(n4)*Cv(C0i+cc1111,ep)
     . +q2(n1)*q2(n2)*q2(n3)*q2(n4)*Cv(C0i+cc2222,ep)
     . +pvSPKKK(n1,n2,n3,n4,q2,q1)*Cv(C0i+cc1112,ep)
     . +pvSPKKK(n1,n2,n3,n4,q1,q2)*Cv(C0i+cc1222,ep)
     . +pvSPPKK(n1,n2,n3,n4,q1,q2)*Cv(C0i+cc1122,ep)
     . +pvSDDPP(n1,n2,n3,n4,q1)*Cv(C0i+cc0011,ep)
     . +pvSDDPP(n1,n2,n3,n4,q2)*Cv(C0i+cc0022,ep)
     . +pvSDDPK(n1,n2,n3,n4,q1,q2)*Cv(C0i+cc0012,ep)
     . +pvSDDDD(n1,n2,n3,n4)*Cv(C0i+cc0000,ep)


      enddo
      enddo
      enddo
      enddo
      enddo

      if ((maxcindex .eq. 4) .and. (pvRespectmaxcindex)) then
        call pvCcheck(4,q1,q2,m1s,m2s,m3s,
     &   FC0,FC1,FC2,FC3,FC4,FC5,FC6,failed)
      if (failed) then
c        write(6,*) 'recursion in pvCtensor'
        itry=itry+1
        goto 11
      endif
        return
      endif

      do ep=-2,0
      do n1=1,4
      do n2=n1,4
      do n3=n2,4
      do n4=n3,4
      do n5=n4,4

      FC5(y5(n1,n2,n3,n4,n5),ep)=
     . +Cv(C0i+cc00001,ep)*pvSDDDDP(n1,n2,n3,n4,n5,q1)
     . +Cv(C0i+cc00002,ep)*pvSDDDDP(n1,n2,n3,n4,n5,q2)
     . +Cv(C0i+cc00111,ep)*pvSDDPPP(n1,n2,n3,n4,n5,q1)
     . +Cv(C0i+cc00112,ep)*pvSDDPPK(n1,n2,n3,n4,n5,q1,q2)
     . +Cv(C0i+cc00122,ep)*pvSDDPPK(n1,n2,n3,n4,n5,q2,q1)
     . +Cv(C0i+cc00222,ep)*pvSDDPPP(n1,n2,n3,n4,n5,q2)
     . +Cv(C0i+cc11111,ep)*q1(n1)*q1(n2)*q1(n3)*q1(n4)*q1(n5)
     . +Cv(C0i+cc11112,ep)*pvSPPPPK(n1,n2,n3,n4,n5,q1,q2)
     . +Cv(C0i+cc11122,ep)*pvSPPPKK(n1,n2,n3,n4,n5,q1,q2)
     . +Cv(C0i+cc11222,ep)*pvSPPPKK(n1,n2,n3,n4,n5,q2,q1)
     . +Cv(C0i+cc12222,ep)*pvSPPPPK(n1,n2,n3,n4,n5,q2,q1)
     . +Cv(C0i+cc22222,ep)*q2(n1)*q2(n2)*q2(n3)*q2(n4)*q2(n5)


      enddo
      enddo
      enddo
      enddo
      enddo
      enddo

      if ((maxcindex .eq. 5) .and. (pvRespectmaxcindex)) then
        call pvCcheck(5,q1,q2,m1s,m2s,m3s,
     &   FC0,FC1,FC2,FC3,FC4,FC5,FC6,failed)
      if (failed) then
c        write(6,*) 'recursion in pvCtensor'
        itry=itry+1
        goto 11
      endif
        return
      endif

      do ep=-2,0
      do n1=1,4
      do n2=n1,4
      do n3=n2,4
      do n4=n3,4
      do n5=n4,4
      do n6=n5,4
      FC6(y6(n1,n2,n3,n4,n5,n6),ep)=
     .  +Cv(C0i+cc000000,ep)*pvSDDDDDD(n1,n2,n3,n4,n5,n6)
     .  +Cv(C0i+cc000011,ep)*pvSDDDDPP(n1,n2,n3,n4,n5,n6,q1)
     .  +Cv(C0i+cc000012,ep)*pvSDDDDPK(n1,n2,n3,n4,n5,n6,q1,q2)
     .  +Cv(C0i+cc000022,ep)*pvSDDDDPP(n1,n2,n3,n4,n5,n6,q2)
     .  +Cv(C0i+cc001111,ep)*pvSDDPPPP(n1,n2,n3,n4,n5,n6,q1)
     .  +Cv(C0i+cc001112,ep)*pvSDDPPPK(n1,n2,n3,n4,n5,n6,q1,q2)
     .  +Cv(C0i+cc001122,ep)*pvSDDPPKK(n1,n2,n3,n4,n5,n6,q1,q2)
     .  +Cv(C0i+cc001222,ep)*pvSDDPKKK(n1,n2,n3,n4,n5,n6,q1,q2)
     .  +Cv(C0i+cc002222,ep)*pvSDDPPPP(n1,n2,n3,n4,n5,n6,q2)
     .  +Cv(C0i+cc111111,ep)*q1(n1)*q1(n2)*q1(n3)*q1(n4)*q1(n5)*q1(n6)
     .  +Cv(C0i+cc111112,ep)*pvSPPPPPK(n1,n2,n3,n4,n5,n6,q1,q2)
     .  +Cv(C0i+cc111122,ep)*pvSPPPPKK(n1,n2,n3,n4,n5,n6,q1,q2)
     .  +Cv(C0i+cc111222,ep)*pvSPPPKKK(n1,n2,n3,n4,n5,n6,q1,q2)
     .  +Cv(C0i+cc112222,ep)*pvSPPPPKK(n1,n2,n3,n4,n5,n6,q2,q1)
     .  +Cv(C0i+cc122222,ep)*pvSPPPPPK(n1,n2,n3,n4,n5,n6,q2,q1)
     .  +Cv(C0i+cc222222,ep)*q2(n1)*q2(n2)*q2(n3)*q2(n4)*q2(n5)*q2(n6)


      enddo
      enddo
      enddo
      enddo
      enddo
      enddo
      enddo

      if ((maxcindex .eq. 6) .and. (pvRespectmaxcindex)) then
        if (pvCitry(C0i) .eq. -1) then
        call pvCcheck(6,q1,q2,m1s,m2s,m3s,
     &   FC0,FC1,FC2,FC3,FC4,FC5,FC6,failed)
      if (failed) then
c          write(6,*) 'recursion in pvCtensor'
        itry=itry+1
        goto 11
      endif
      pvCitry(C0i)=itry
c        if (itry .gt. 0) then
c        write(6,*) 'pvCtensor success: itry=',itry
c        endif
        endif
        return
      endif

      do ep=-2,0
      do n1=1,4
      do n2=n1,4
      do n3=n2,4
      do n4=n3,4
      do n5=n4,4
      do n6=n5,4
      do n7=n6,4
c--- crude implementation of FC7 (used for checking only)
      include 'lib/TensorReduction/Include/pvFC7.f'
      enddo
      enddo
      enddo
      enddo
      enddo
      enddo
      enddo
      enddo
      
      return
      end