ChebyshevGaussNodesAndWeights Subroutine

SUBROUTINE ChebyshevGaussNodesAndWeights(N_in,xGP,wGP)
IMPLICIT NONE
!----------------------------------------------------------------------------------------------------------------------------------
! INPUT/OUTPUT VARIABLES
INTEGER,INTENT(IN)        :: N_in         !! polynomial degree, (N_in+1) CLpoints
REAL(wp),INTENT(OUT)          :: xGP(0:N_in)  !! Gauss point positions for the reference interval [-1,1]
REAL(wp),INTENT(OUT),OPTIONAL :: wGP(0:N_in)  !! Gauss point integration weights
!----------------------------------------------------------------------------------------------------------------------------------
! LOCAL VARIABLES
INTEGER                   :: iGP
!==================================================================================================================================
DO iGP=0,N_in
  xGP(iGP)=-cos(REAL(2*iGP+1,wp)/REAL(2*N_in+2,wp)*PP_Pi)
END DO
IF(PRESENT(wGP))THEN
  DO iGP=0,N_in
    wGP(iGP)=PP_Pi/REAL(N_in+1,wp)
  END DO
END IF
END SUBROUTINE ChebyshevGaussNodesAndWeights