rkSum.f90

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SUBROUTINE rksum(N1,N2,N3,localInterval,h,K1,K2,K3,K4,stateData)

  INTEGER(KIND=8), INTENT(IN)    :: N1, N2, N3, localInterval(6)
  REAL(KIND=8),    INTENT(IN)    :: h
  REAL(KIND=8),    INTENT(IN)    :: K1(n1*n2*n3)
  REAL(KIND=8),    INTENT(IN)    :: K2(n1*n2*n3)
  REAL(KIND=8),    INTENT(IN)    :: K3(n1*n2*n3)
  REAL(KIND=8),    INTENT(IN)    :: K4(n1*n2*n3)
  REAL(KIND=8),    INTENT(INOUT) :: stateData(n1*n2*n3)

  INTEGER(KIND=8) :: I, J, K, LI, LIK, LIJ, IS1, IE1
  INTEGER(KIND=8) :: xyPlane
  INTEGER(KIND=8) :: S1,E1,S2,E2,S3,E3
  REAL(KIND=8)    :: fac1,fac2

  fac1 = h/6.0_8
  fac2 = h/3.0_8

  s1 = localinterval(1)
  e1 = localinterval(2)
  s2 = localinterval(3)
  e2 = localinterval(4)
  s3 = localinterval(5)
  e3 = localinterval(6)

  xyplane = (n1*n2)
  
  DO k = s3, e3
     lik = (k-1)*xyplane
     DO j = s2, e2
        lij = (j-1)*n1 + lik
        DO i = s1, e1
           li = lij + i
           statedata(li) = fac1*(k1(li)+k4(li)) + fac2*(k2(li) + k3(li)) + statedata(li)
        END DO
     END DO
  END DO
  

END SUBROUTINE rksum