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hit_and_miss.f90
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hit_and_miss.f90
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! hit_and_miss.f90
! Estimates volume of polyhedron by simple MC
PROGRAM hit_and_miss
!------------------------------------------------------------------------------------------------!
! This software was written in 2016/17 !
! by Michael P. Allen <m.p.allen@warwick.ac.uk>/<m.p.allen@bristol.ac.uk> !
! and Dominic J. Tildesley <d.tildesley7@gmail.com> ("the authors"), !
! to accompany the book "Computer Simulation of Liquids", second edition, 2017 ("the text"), !
! published by Oxford University Press ("the publishers"). !
! !
! LICENCE !
! Creative Commons CC0 Public Domain Dedication. !
! To the extent possible under law, the authors have dedicated all copyright and related !
! and neighboring rights to this software to the PUBLIC domain worldwide. !
! This software is distributed without any warranty. !
! You should have received a copy of the CC0 Public Domain Dedication along with this software. !
! If not, see <http://creativecommons.org/publicdomain/zero/1.0/>. !
! !
! DISCLAIMER !
! The authors and publishers make no warranties about the software, and disclaim liability !
! for all uses of the software, to the fullest extent permitted by applicable law. !
! The authors and publishers do not recommend use of this software for any purpose. !
! It is made freely available, solely to clarify points made in the text. When using or citing !
! the software, you should not imply endorsement by the authors or publishers. !
!------------------------------------------------------------------------------------------------!
USE, INTRINSIC :: iso_fortran_env, ONLY : output_unit
IMPLICIT NONE
REAL :: v
REAL, DIMENSION(3) :: r, zeta
REAL, DIMENSION(3), PARAMETER :: r_0 = [1.0, 2.0, 3.0]
REAL, PARAMETER :: v_0 = PRODUCT(r_0)
INTEGER :: tau, tau_shot, tau_hit
CALL RANDOM_SEED()
tau_hit = 0
tau_shot = 1000000
DO tau = 1, tau_shot
CALL RANDOM_NUMBER ( zeta(:) ) ! uniform in range (0,1)
r = zeta * r_0 ! uniform in v_0
IF ( r(2) < ( 2.0 - 2.0*r(1) ) .AND. &
& r(3) < ( 1.0 + r(2) ) ) THEN ! in polyhedron
tau_hit = tau_hit + 1
END IF
END DO
v = v_0 * REAL ( tau_hit ) / REAL ( tau_shot )
WRITE ( unit=output_unit, fmt='(a,f10.5)' ) 'Estimate = ', v
END PROGRAM hit_and_miss