!Copyright (c) 2022 by LEEE under guide of Huaifeng Sun(sunhuaifeng@email.sdu.edu.cn)
!written by Shangbin Liu(lsbin87@126.com)
    
SUBROUTINE Get_Receiver_Gridlabel
	!This subroutine is used to calculate the global coordinates and grid dispersion at the receiving point
	USE CONSTANTPARAMETERS
	USE OMP_LIB
	IMPLICIT NONE
	INTEGER ii,i,j,k
	INTEGER(KIND=4) ::x_pined,y_pined,z_pined
	REAL(KIND=8) ::volu(8),volu_total
	
	! -------------------------points_observer_gridlabel-------------------------------------------!
	!$OMP PARALLEL DO PRIVATE(i,j,k,x_pined,y_pined,z_pined,volu,volu_total)
	DO ii=1,point_num
	DO i=1,NX
		IF(Points_Observer(ii)%Local_Coord_To_Source%Coord_X < Coord_HZ_X(i))THEN				
			x_pined = i-1
			EXIT                    !Find the corresponding grid
		ENDIF
	ENDDO
	x_pined = MAX(1,MIN(x_pined,NX-1))    !clamp: keep the index in [1,NX-1] even if the receiver is outside the grid
	DO j=1,NY
		IF(Points_Observer(ii)%Local_Coord_To_Source%Coord_Y < Coord_HZ_Y(j))THEN
			y_pined = j-1
			EXIT
		ENDIF
	ENDDO
	y_pined = MAX(1,MIN(y_pined,NY-1))    !clamp
	DO k=1,NZB
		IF(Points_Observer(ii)%Local_Coord_To_Source%Coord_Z < Coord_HZ_Z(k))THEN
			z_pined = k-1
			EXIT
		ENDIF
	ENDDO
	z_pined = MAX(1,MIN(z_pined,NZB-1))   !clamp
!The position of the first HZ corresponding to the observation point
		Points_Observer(ii)%Global_Coordmesh(1)%Coordmesh_X = x_pined
		Points_Observer(ii)%Global_Coordmesh(1)%Coordmesh_Y = y_pined
		Points_Observer(ii)%Global_Coordmesh(1)%Coordmesh_Z = z_pined
		!The position of the second HZ corresponding to the observation point
		Points_Observer(ii)%Global_Coordmesh(2)%Coordmesh_X = x_pined + 1
		Points_Observer(ii)%Global_Coordmesh(2)%Coordmesh_Y = y_pined
		Points_Observer(ii)%Global_Coordmesh(2)%Coordmesh_Z = z_pined
		!The position of the 3th HZ corresponding to the observation point
		Points_Observer(ii)%Global_Coordmesh(3)%Coordmesh_X = x_pined
		Points_Observer(ii)%Global_Coordmesh(3)%Coordmesh_Y = y_pined + 1
		Points_Observer(ii)%Global_Coordmesh(3)%Coordmesh_Z = z_pined
		!The position of the 4th HZ corresponding to the observation point
		Points_Observer(ii)%Global_Coordmesh(4)%Coordmesh_X = x_pined + 1
		Points_Observer(ii)%Global_Coordmesh(4)%Coordmesh_Y = y_pined + 1
		Points_Observer(ii)%Global_Coordmesh(4)%Coordmesh_Z = z_pined
		!The position of the 5th HZ corresponding to the observation point
		Points_Observer(ii)%Global_Coordmesh(5)%Coordmesh_X = x_pined
		Points_Observer(ii)%Global_Coordmesh(5)%Coordmesh_Y = y_pined
		Points_Observer(ii)%Global_Coordmesh(5)%Coordmesh_Z = z_pined + 1
		!The position of the 6th HZ corresponding to the observation point
		Points_Observer(ii)%Global_Coordmesh(6)%Coordmesh_X = x_pined + 1
		Points_Observer(ii)%Global_Coordmesh(6)%Coordmesh_Y = y_pined
		Points_Observer(ii)%Global_Coordmesh(6)%Coordmesh_Z = z_pined + 1
		!The position of the 7th HZ corresponding to the observation point
		Points_Observer(ii)%Global_Coordmesh(7)%Coordmesh_X = x_pined
		Points_Observer(ii)%Global_Coordmesh(7)%Coordmesh_Y = y_pined + 1
		Points_Observer(ii)%Global_Coordmesh(7)%Coordmesh_Z = z_pined + 1
		!The position of the 8th HZ corresponding to the observation point
		Points_Observer(ii)%Global_Coordmesh(8)%Coordmesh_X = x_pined + 1
		Points_Observer(ii)%Global_Coordmesh(8)%Coordmesh_Y = y_pined + 1
		Points_Observer(ii)%Global_Coordmesh(8)%Coordmesh_Z = z_pined + 1
		
		volu(1) = (Points_Observer(ii)%Local_Coord_To_Source%Coord_X - Coord_HZ_X(x_pined)) * (Points_Observer(ii)%Local_Coord_To_Source%Coord_Y- Coord_HZ_Y(y_pined)) *&
				 (Points_Observer(ii)%Local_Coord_To_Source%Coord_Z - Coord_HZ_Z(z_pined))
		volu(2) = (Coord_HZ_X(x_pined+1) - Points_Observer(ii)%Local_Coord_To_Source%Coord_X) * (Points_Observer(ii)%Local_Coord_To_Source%Coord_Y- Coord_HZ_Y(y_pined)) *&
				 (Points_Observer(ii)%Local_Coord_To_Source%Coord_Z - Coord_HZ_Z(z_pined))
		volu(3) = (Points_Observer(ii)%Local_Coord_To_Source%Coord_X - Coord_HZ_X(x_pined)) * (Coord_HZ_Y(y_pined+1) - Points_Observer(ii)%Local_Coord_To_Source%Coord_Y) *&
				 (Points_Observer(ii)%Local_Coord_To_Source%Coord_Z - Coord_HZ_Z(z_pined))
		volu(4) = (Coord_HZ_X(x_pined+1) - Points_Observer(ii)%Local_Coord_To_Source%Coord_X) * (Coord_HZ_Y(y_pined+1) - Points_Observer(ii)%Local_Coord_To_Source%Coord_Y) *&
				 (Points_Observer(ii)%Local_Coord_To_Source%Coord_Z - Coord_HZ_Z(z_pined))
		volu(5) = (Points_Observer(ii)%Local_Coord_To_Source%Coord_X - Coord_HZ_X(x_pined)) * (Points_Observer(ii)%Local_Coord_To_Source%Coord_Y- Coord_HZ_Y(y_pined)) *&
				 (Coord_HZ_Z(z_pined+1) - Points_Observer(ii)%Local_Coord_To_Source%Coord_Z)
		volu(6) = (Coord_HZ_X(x_pined+1) - Points_Observer(ii)%Local_Coord_To_Source%Coord_X) * (Points_Observer(ii)%Local_Coord_To_Source%Coord_Y- Coord_HZ_Y(y_pined)) *&
				 (Coord_HZ_Z(z_pined+1) - Points_Observer(ii)%Local_Coord_To_Source%Coord_Z)
		volu(7) = (Points_Observer(ii)%Local_Coord_To_Source%Coord_X - Coord_HZ_X(x_pined)) * (Coord_HZ_Y(y_pined+1) - Points_Observer(ii)%Local_Coord_To_Source%Coord_Y) *&
				 (Coord_HZ_Z(z_pined+1) - Points_Observer(ii)%Local_Coord_To_Source%Coord_Z)
		volu(8) = (Coord_HZ_X(x_pined+1) - Points_Observer(ii)%Local_Coord_To_Source%Coord_X) * (Coord_HZ_Y(y_pined+1) - Points_Observer(ii)%Local_Coord_To_Source%Coord_Y) *&
				 (Coord_HZ_Z(z_pined+1) - Points_Observer(ii)%Local_Coord_To_Source%Coord_Z)
		
		volu_total = (Coord_HZ_X(x_pined+1) - Coord_HZ_X(x_pined)) * (Coord_HZ_Y(y_pined+1) - Coord_HZ_Y(y_pined)) * (Coord_HZ_Z(z_pined+1) - Coord_HZ_Z(z_pined))
		
		Points_Observer(ii)%Coeff(1) = volu(8)/volu_total
		Points_Observer(ii)%Coeff(2) = volu(7)/volu_total
		Points_Observer(ii)%Coeff(3) = volu(6)/volu_total
		Points_Observer(ii)%Coeff(4) = volu(5)/volu_total
		Points_Observer(ii)%Coeff(5) = volu(4)/volu_total
		Points_Observer(ii)%Coeff(6) = volu(3)/volu_total
		Points_Observer(ii)%Coeff(7) = volu(2)/volu_total
		Points_Observer(ii)%Coeff(8) = volu(1)/volu_total
	ENDDO
	!$OMP END PARALLEL DO
	!------------------------------------------------------------------------------------------!   
	RETURN
ENDSUBROUTINE Get_Receiver_Gridlabel