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Release 0.5 of Electric Field Monte Carlo code (EMC)

Dr. Min Xu <>

1. Pre-requirements
EMC depends on the installation of certain softwares.

(a) a C++ compiler
   GNU C++ should be fine. The compiler should support templates.
(b) MIEV package by Dr. Warren J. Wiscombe
   This is an excellent code for Mie calculations.

(c) mtwist-0.5 package by Prof. Geoff Kuenning at Harvey Mudd College
   This is an Mersenne Twist Pseudorandom Number Generator
   Package. The Mersenne Twist method for generating pseudorandom 
   numbers is an extremely fast, flexible, and desirable approach to
   random-number generation. It has superb statistical properties and
   a ridiculously long period (2^19937-1).

(d) Netcdf package (optional)
   Netcdf API is used in some examples coming with EMC to store
   simulation outputs. The benefit of using netcdf files is the
   platform-independence of these files.

I have included parts of (a-c) in the distribution only for the purpose 
your convenience. Full credit should be given to respective authors.

2. EMC
EMC package is implemented in C++ and contained in three headers
files. We use x as the size parameter of the particle, m the complex
relative refractive index, S1 and S2 are the diagonal elements of the
amplitude scattering matrix (whose off-diagonal elements are zero) in 
convention of Hulst.

dmiev.h:	a C interface for MIEV package, used by scatterer.h

scatterer.h:	a C++ header implementing a class "scatterer". The key
		methods include: 
		 // N and nslot can be increased for a higher accuracy
		 // of the forward and inverse table.
		 scatterer(double x, dcmplx m, int N=10001, int nslot=10000);
		 // obtain S1 and S2 at a list of cosines of angles of
		 // length n
		 phasef(int n, double* mu, dcmplx* s1, dcmplx* s2);
		 // obtain S1 and S2 at the cosine of one angle mu
		 phasef(double mu, dcmplx* s1, dcmplx* s2);

		 // a quicker version using the lookup table pre-computed
		 phasef_lu(double mu, dcmplx* s1, dcmplx* s2);

		 // yield the scattering angle given the probability
		 // within (0,1) using the inverse table pre-computed
		 draw_mu(double p);

pol_montecarlo.h:	the core header file of EMC implementing a
		class "photonPacket". The key methods include:

		 // initialization
		 photonPacket(const scatterer* sct, char* fname=NULL,
		 unsigned long seed=0); 
		 // launch the photons. The incident electric field is
		 // given by (E1, E2) where light is propagating in the
		 // direction (u, v, w), E1 is in the direction (l, m,
		 // n), and E2 is in the direction specified by the cross 
		 // product of the above two directions. Light is
		 // incident upon the position (x,y,z) at time t. The
		 // incident light intensity must be unity (|E1|^2 +
		 // |E2|^2=1) and the directions must be unit vectors.
		 void launch(dcmplx E1=1, dcmplx E2=0, double l=1,
		 double m=0, double n=0, double u=0, double v=0,
		 double w=1, double x=0, double y=0, double z=0,
		 double t=0); 

		 // move to next scattering or absorption event
		 void move();

		 // absorption event
		 void absorb();

		 // scattering event
		 void scatter();

		 // next event estimator of (Ed1, Ed2) with the
                 // direction vector Q at time td crossing the boundary
                 // z=zd in the direction (ud, vd, wd) 
		 void pointestimator(double *td, double *deposit,
                 double Q[3][3], dcmplx *Ed1, dcmplx *Ed2, double zd,
                 double ud=0, double vd=0, double wd=1); 

		The photon status is stored in the public data members
                of the class, they are:

		 xold, yold, zold, told:
		 the position and time of the previous scattering

		 x, y, z, t, weight:
		 the current position and time of photon and its weight

		 E1, E2:
		 electric field components

		 (l, m, n) the unit vector for E1 direction
		 (p, q, r) the unit vector for E2 direction
		 (u, v, w) the propagation direction

		 number of scattering events
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