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/*------------------------------------------------------------------------
 * Copyright (C) 2011 For the list of authors, see file AUTHORS.
 *
 * This file is part of SOFI2D.
 *
 * SOFI2D is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, version 2.0 of the License only.
 *
 * SOFI2D is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with SOFI2D. See file COPYING and/or
  * <http://www.gnu.org/licenses/gpl-2.0.html>.
--------------------------------------------------------------------------*/
/*  ----------------------------------------------------------------------
 *  This is program SOFI2D.
 *  Parallel 2-D Viscoelastic Finite Difference Seismic Modeling
 *  using the Standard Staggered Grid (SSG)
 *
 *  PLEASE DO NOT DISTRIBUTE. PLEASE REFER OTHER PEOPLE TO :
 *
 *  Prof. Dr. Thomas Bohlen, Karlsruhe Institute of Technology,
 *  Geophysical Institute,
 *  Hertzstr. 16, 76187 Karlsruhe, Germany
 *  Phone/Fax: +49 (0)721 608 44416
 *  mailto:thomas.bohlen@kit.edu,
 *  http://www.gpi.kit.edu/
 *  http://www.gpi.kit.edu/SOFI2D.php
 *
 *  If you want to publish synthetic data calculated with this program please
 *  give a reference to the following paper:
 *  Bohlen, T., 2002, Parallel 3-D viscoelastic finite-difference seismic modelling,
 *  Computers @ Geopsciences, Vol. 28, No. 8, 887-889.
 *
 *  ----------------------------------------------------------------------*/

/* $Id: sofi2D.c 865 2015-09-22 12:57:11Z tmetz $ */

#include "fd.h"           /* general include file for viscoelastic FD programs */

#include "globvar.h"      /* definition of global variables  */

int main ( int argc, char **argv )
{
	/* variables in main */
	int ns, nseismograms = 0, nt, nd, fdo3;
	int lsnap, nsnap = 0, lsamp = 0, buffsize;
	int ntr = 0, ntr_loc = 0, ntr_glob = 0, nsrc = 0, nsrc_loc = 0;
	int ishot, nshots; /* Added ishot and nshots for multiple shots */
	/*Limits for local grids defined in subgrid_bounds.c */
	int * gx=NULL, * gy=NULL;

	float memdyn, memmodel, memseismograms, membuffer, memtotal, memcpml=0.0;
	float fac1, fac2;
	char *buff_addr, ext[10], *fileinp = "", modestr[10], infostr[70];
	double time1 = 0.0, time2 = 0.0, time3 = 0.0, time4 = 0.0;
	double time5 = 0.0, time6 = 0.0, time7 = 0.0, time8 = 0.0;
	double time_av_v_update = 0.0, time_av_s_update = 0.0,
	       time_av_v_exchange = 0.0, time_av_s_exchange = 0.0, time_av_timestep = 0.0;

	float **psxx = NULL, **psxy = NULL, **psyy = NULL;
	float **pvx = NULL, **pvy = NULL, ***pr = NULL;
	float ***pp = NULL, ***pq = NULL;
	float **pu = NULL, **puipjp = NULL, **ptaus = NULL, **ptaup = NULL,
	        *etaip = NULL, *etajm = NULL, *peta = NULL, **ptausipjp = NULL,
	         **fipjp = NULL, ***dip = NULL, *bip = NULL, *bjm = NULL, *cip = NULL,
	           *cjm = NULL, ***d = NULL, ***e = NULL, **f = NULL, **g = NULL;
	float **prho = NULL, **prip = NULL, **prjp = NULL, **ppi = NULL;

	float **sectionvx = NULL, **sectionvy = NULL, **sectionp = NULL,
	        **sectioncurl = NULL, **sectiondiv = NULL;
	float **absorb_coeff = NULL;
	float **srcpos = NULL, **srcpos_loc = NULL, **signals = NULL, *hc = NULL,
	        **srcpos_current = NULL;
	int **recpos = NULL, **recpos_loc = NULL;

	float **bufferlef_to_rig = NULL, **bufferrig_to_lef = NULL,
	        **buffertop_to_bot = NULL, **bufferbot_to_top = NULL;

	float ** seismo_fulldata=NULL;
	int * recswitch = NULL;

	/* PML variables */
	float * d_x=NULL, * K_x=NULL, * alpha_prime_x=NULL, * a_x=NULL, * b_x=NULL, * d_x_half=NULL,
	        * K_x_half=NULL, * alpha_prime_x_half=NULL, * a_x_half=NULL, * b_x_half=NULL,
	          * d_y=NULL, * K_y=NULL, * alpha_prime_y=NULL, * a_y=NULL, * b_y=NULL, * d_y_half=NULL,
	            * K_y_half=NULL, * alpha_prime_y_half=NULL, * a_y_half=NULL, * b_y_half=NULL;
	float ** psi_sxx_x=NULL, ** psi_syy_y=NULL, ** psi_sxy_y=NULL, ** psi_sxy_x=NULL,
	         ** psi_vxx=NULL, ** psi_vyy=NULL, ** psi_vxy=NULL, ** psi_vyx=NULL, ** psi_vxxs=NULL;


	FILE *fpinp;

	MPI_Request *req_send, *req_rec;
	/*	MPI_Status *send_statuses, *rec_statuses; */



	/* Initialize MPI environment */
	MPI_Init ( &argc, &argv );
	MPI_Comm_size ( MPI_COMM_WORLD, &NP );
	MPI_Comm_rank ( MPI_COMM_WORLD, &MYID );

	if ( MYID == 0 ) {
		time1 = MPI_Wtime();
		clock();
	}

	/* print program name, version etc to stdout*/
	if ( MYID == 0 )
		info ( stdout );

	/* =================================================== */

	/* check of parameter-file can be opened*/
	fileinp = argv[1];
	fpinp = fopen ( fileinp, "r" );
	if ( fpinp == NULL ) {
		if ( MYID == 0 ) {
			printf (
			    "\n==================================================================\n" );
			printf ( " Cannot open sofi2D input file %s \n", fileinp );
			printf (
			    "\n==================================================================\n\n" );
			err ( " --- " );
			return 0;
		}
	} else {
		fscanf ( fpinp, "%s %s = %i", infostr, modestr, &RUNMODE );
		fclose ( fpinp );
	}

	/* Check file system */
	check_fs ( stdout, argc, fileinp );

	/* =================================================== */
	if ( RUNMODE == 0 ) {
		/* read standard input file */
		if ( strstr ( fileinp, ".json" ) )
			//read json formated input file
			read_par_json ( stdout, fileinp );
		else   {
		        if ( MYID == 0 ) 
			err ( " Old Input files (.inp) are no longer supported. \n Please use .json input files instead. " );
			
		}
	}
	/*else
		 auto mode: read input files 
		read_par_auto ( stdout, fileinp ); */
	/* =================================================== */

	exchange_par();

	/* open log-file (each PE is using different file) */
	sprintf ( ext, ".%i", MYID );
	strcat ( LOG_FILE, ext );

	/* nodes MYIDo writes logging info to LOG_FILE or stdout */
	if ( MYID == 0 )
		switch ( LOG ) {
		case 0:
			FP = fopen ( "/dev/null", "w" ); /* no logging information will be output */
			break;
		case 1:
			FP = stdout; /* logging information will be written to standard output */
			break;
		case 2:
			if ( ( FP = fopen ( LOG_FILE, "w" ) ) == NULL )
				err ( " Opening log-file failed." );
			/* logging information will be written to LOG_FILE */
			break;
		}
	/* all other nodes write logging info to LOG_FILE */
	if ( MYID > 0 ) {
		if ( ( FP = fopen ( LOG_FILE, "w" ) ) == NULL )
			err ( " Opening log-file failed." );
		fprintf ( FP, " This is the log-file %s generated by PE %d \n\n",
		          LOG_FILE, MYID );
	}

	if ( MYID == 0 )
		note ( FP );

	/* domain decomposition */
	initproc();

	NT = iround ( TIME/DT ); /* number of timesteps */
	ns = iround ( NT/NDT ); /* number of samples per trace */
	lsnap = iround ( TSNAP1/DT ); /* first snapshot at this timestep */
	lsamp = NDT;

	/* output of parameters to log-file or stdout */
	if ( MYID == 0 )
		write_par ( FP );

	/* For the Rotated Staggered Grid only second order FD operators are implemented 
	if ( RSG ) {
		if ( FDORDER > 2 )
			err ( " For the Rotated Staggered Grid only second order FD operators are implemented. Please revise parameter FDORDER in the input file! " );
		
	}*/

	/* NXG, NYG denote size of the entire (global) grid */
	NXG = NX;
	NYG = NY;

	/* In the following, NX and NY denote size of the local grid ! */
	NX = IENDX;
	NY = IENDY;

	if ( SEISMO ) {
		recpos = receiver ( FP, &ntr );
		recswitch = ivector ( 1, ntr );
		recpos_loc = splitrec ( recpos, &ntr_loc, ntr, recswitch );
		ntr_glob = ntr;
		ntr = ntr_loc;
	}

	/* allocate buffer for seismogram output, merged seismogram section of all PEs */
	if ( SEISMO ) seismo_fulldata=matrix ( 1,ntr_glob,1,ns );

	/* number of seismogram sections which have to be stored in core memory*/
	/* allocation of memory for seismogramm merge */
	switch ( SEISMO ) {
	case 1: /* particle velocities only */
		nseismograms = 3;
		break;
	case 2: /* pressure only */
		nseismograms = 1;
		break;
	case 3: /* curl and div only */
		nseismograms = 2;
		break;
	case 4: /* everything */
		nseismograms = 6;
		break;
	default:
		nseismograms = 1;
		break;
	}

	/*allocate memory for dynamic, static and buffer arrays */
	nd = FDORDER / 2 + 1;
	fdo3 = 2 * nd;

	fac1 = ( NX + fdo3 ) * ( NY + fdo3 );
	fac2 = sizeof ( float ) * pow ( 2.0, -20.0 );

	if ( L ) {
		memdyn = ( 5.0 + 3.0 * ( float ) L ) * fac1 * fac2;
		memmodel = ( 12.0 + 3.0 * ( float ) L ) * fac1 * fac2 + NX * NY * fac2;
	} else {
		memdyn = 5.0 * fac1 * fac2;
		memmodel = 6.0 * fac1 * fac2 + NX * NY * fac2;
	}

	memseismograms = nseismograms * ntr * ns * fac2;
	membuffer = 2.0 * fdo3 * ( NY + NX ) * fac2;
	buffsize = 2.0 * 2.0 * fdo3 * ( NX + NY ) * sizeof ( MPI_FLOAT );
	if ( ABS_TYPE==1 ) memcpml=2.0*FW*4.0* ( NY+NX ) *fac2+20.0*2.0*FW*fac2;
	memtotal = memdyn + memmodel + memseismograms + membuffer +memcpml
	           + ( buffsize * pow ( 2.0, -20.0 ) );

	if ( MYID == 0 ) {
		fprintf ( FP, "\n **Message from main (printed by PE %d):\n", MYID );
		fprintf ( FP, " Size of local grids: NX=%d \t NY=%d\n", NX, NY );
		fprintf ( FP, " Each process is now trying to allocate memory for:\n" );
		fprintf ( FP, " Dynamic variables: \t\t %6.2f MB\n", memdyn );
		fprintf ( FP, " Static variables: \t\t %6.2f MB\n", memmodel );
		fprintf ( FP, " Seismograms: \t\t\t %6.2f MB\n", memseismograms );
		fprintf ( FP, " Buffer arrays for grid exchange:%6.2f MB\n", membuffer );
		fprintf ( FP, " Network Buffer for MPI_Bsend: \t %6.2f MB\n",
		          buffsize * pow ( 2.0, -20.0 ) );
		if ( ABS_TYPE==1 ) fprintf ( FP, " CPML variables: \t\t %6.2f MB\n", memcpml );
		fprintf ( FP, " ------------------------------------------------ \n" );
		fprintf ( FP, " Total memory required: \t %6.2f MB.\n\n", memtotal );
	}

	/* allocate buffer for buffering messages */
	buff_addr = malloc ( buffsize );
	if ( !buff_addr )
		err ( "allocation failure for buffer for MPI_Bsend !" );
	MPI_Buffer_attach ( buff_addr, buffsize );

	/* allocation for request and status arrays */
	req_send = ( MPI_Request * ) malloc ( REQUEST_COUNT * sizeof ( MPI_Request ) );
	req_rec = ( MPI_Request * ) malloc ( REQUEST_COUNT * sizeof ( MPI_Request ) );
	/*	send_statuses = (MPI_Status *) malloc(REQUEST_COUNT * sizeof(MPI_Status));
		rec_statuses = (MPI_Status *) malloc(REQUEST_COUNT * sizeof(MPI_Status)); */



	/* ------------ memory allocation for arrays ------------- */
	/* subgrid arrays*/
	gy = ivector ( 1,4 );
	gx = ivector ( 1,4 );

	/* dynamic (wavefield) arrays (elastic + viscoelastic) */


	psxx = matrix ( -nd + 1, NY + nd, -nd + 1, NX + nd );
	psxy = matrix ( -nd + 1, NY + nd, -nd + 1, NX + nd );
	psyy = matrix ( -nd + 1, NY + nd, -nd + 1, NX + nd );
	pvx = matrix ( -nd + 1, NY + nd, -nd + 1, NX + nd );
	pvy = matrix ( -nd + 1, NY + nd, -nd + 1, NX + nd );


	if ( ABS_TYPE==1 ) {
		/* PML */
		d_x = vector ( 1,2*FW );
		K_x = vector ( 1,2*FW );
		alpha_prime_x = vector ( 1,2*FW );
		a_x = vector ( 1,2*FW );
		b_x = vector ( 1,2*FW );

		d_x_half = vector ( 1,2*FW );
		K_x_half = vector ( 1,2*FW );
		alpha_prime_x_half = vector ( 1,2*FW );
		a_x_half = vector ( 1,2*FW );
		b_x_half = vector ( 1,2*FW );

		d_y = vector ( 1,2*FW );
		K_y = vector ( 1,2*FW );
		alpha_prime_y = vector ( 1,2*FW );
		a_y = vector ( 1,2*FW );
		b_y = vector ( 1,2*FW );

		d_y_half = vector ( 1,2*FW );
		K_y_half = vector ( 1,2*FW );
		alpha_prime_y_half = vector ( 1,2*FW );
		a_y_half = vector ( 1,2*FW );
		b_y_half = vector ( 1,2*FW );

		psi_sxx_x =  matrix ( 1,NY,1,2*FW );
		psi_syy_y =  matrix ( 1,2*FW,1,NX );
		psi_sxy_y =  matrix ( 1,2*FW,1,NX );
		psi_sxy_x =  matrix ( 1,NY,1,2*FW );

		psi_vxx   =  matrix ( 1,NY,1,2*FW );
		psi_vyy   =  matrix ( 1,2*FW,1,NX );
		psi_vxy   =  matrix ( 1,2*FW,1,NX );
		psi_vyx   =  matrix ( 1,NY,1,2*FW );

		psi_vxxs  =  matrix ( 1,NY,1,2*FW ); /* For surface_elastic(visc).c*/
	}

	/* dynamic (wavefield) arrays (viscoelastic) */
	if ( L > 0 ) {
		pr = f3tensor ( -nd + 1, NY + nd, -nd + 1, NX + nd, 1, L );
		pp = f3tensor ( -nd + 1, NY + nd, -nd + 1, NX + nd, 1, L );
		pq = f3tensor ( -nd + 1, NY + nd, -nd + 1, NX + nd, 1, L );
	}


	/* static (model) arrays (elastic + viscoelastic) */
	prho = matrix ( -nd + 1, NY + nd, -nd + 1, NX + nd );
	prip = matrix ( -nd + 1, NY + nd, -nd + 1, NX + nd );
	prjp = matrix ( -nd + 1, NY + nd, -nd + 1, NX + nd );
	ppi = matrix ( -nd + 1, NY + nd, -nd + 1, NX + nd );
	pu = matrix ( -nd + 1, NY + nd, -nd + 1, NX + nd );
	puipjp = matrix ( -nd + 1, NY + nd, -nd + 1, NX + nd );
	absorb_coeff = matrix ( 1, NY, 1, NX );

	/* static (model) arrays (viscoelastic) */
	if ( L > 0 ) {
		dip = f3tensor ( -nd + 1, NY + nd, -nd + 1, NX + nd, 1, L );
		d = f3tensor ( -nd + 1, NY + nd, -nd + 1, NX + nd, 1, L );
		e = f3tensor ( -nd + 1, NY + nd, -nd + 1, NX + nd, 1, L );
		ptaus = matrix ( -nd + 1, NY + nd, -nd + 1, NX + nd );
		ptausipjp = matrix ( -nd + 1, NY + nd, -nd + 1, NX + nd );
		ptaup = matrix ( -nd + 1, NY + nd, -nd + 1, NX + nd );
		fipjp = matrix ( -nd + 1, NY + nd, -nd + 1, NX + nd );
		f = matrix ( -nd + 1, NY + nd, -nd + 1, NX + nd );
		g = matrix ( -nd + 1, NY + nd, -nd + 1, NX + nd );
		peta = vector ( 1, L );
		etaip = vector ( 1, L );
		etajm = vector ( 1, L );
		bip = vector ( 1, L );
		bjm = vector ( 1, L );
		cip = vector ( 1, L );
		cjm = vector ( 1, L );
	}

	/* memory allocation for buffer arrays in which the wavefield
	 information to be exchanged between neighboring PEs is stored */

	/*if ( RSG ) {
		// in the RSG case fdo3 is always 4
		bufferlef_to_rig = matrix ( 0, NY + 1, 1, fdo3 );
		bufferrig_to_lef = matrix ( 0, NY + 1, 1, fdo3 );
		buffertop_to_bot = matrix ( 1, NX, 1, fdo3 );
		bufferbot_to_top = matrix ( 1, NX, 1, fdo3 );

	} else {*/

		bufferlef_to_rig = matrix ( 1, NY, 1, fdo3 );
		bufferrig_to_lef = matrix ( 1, NY, 1, fdo3 );
		buffertop_to_bot = matrix ( 1, NX, 1, fdo3 );
		bufferbot_to_top = matrix ( 1, NX, 1, fdo3 );
	

	if ( ntr > 0 ) {
		switch ( SEISMO ) {
		case 1: /* particle velocities only */
			sectionvx = matrix ( 1, ntr, 1, ns );
			sectionvy = matrix ( 1, ntr, 1, ns );
			break;
		case 2: /* pressure only */
			sectionp = matrix ( 1, ntr, 1, ns );
			break;
		case 3: /* curl and div only */
			sectioncurl = matrix ( 1, ntr, 1, ns );
			sectiondiv = matrix ( 1, ntr, 1, ns );
			break;
		case 4: /* everything */
			sectionvx = matrix ( 1, ntr, 1, ns );
			sectionvy = matrix ( 1, ntr, 1, ns );
			sectioncurl = matrix ( 1, ntr, 1, ns );
			sectiondiv = matrix ( 1, ntr, 1, ns );
			sectionp = matrix ( 1, ntr, 1, ns );
			break;
		}
	}

	/* memory for source position definition for saving the current positions */
	srcpos_current = matrix ( 1, 8, 1, 1 );

	fprintf ( FP, " ... memory allocation for PE %d was successfull.\n\n", MYID );

	/* Holberg coefficients for FD operators*/
	hc = holbergcoeff();

	/* Reading source positions from SOURCE_FILE */
	srcpos = sources ( &nsrc );

	MPI_Barrier ( MPI_COMM_WORLD );

	/* output source signal e.g. for cross-correlation of comparison with analytical solutions */
	/*if (nsrc_loc>0){
	 char  source_signal_file[STRING_SIZE];
	 sprintf(source_signal_file,"source_signal.%d.su",MYID);
	 fprintf(stdout,"\n PE %d outputs source time function in SU format to %s \n ", MYID, source_signal_file);
	 output_source_signal(fopen(source_signal_file,"w"), signals, NT, 1);
	 }
	 */

	/* create model grids */

	/* viscoelastic model */
	if ( L ) {
		if ( READMOD )
			readmod_visco ( prho, ppi, pu, ptaus, ptaup, peta );
		else

			model_visco ( prho, ppi, pu, ptaus, ptaup, peta );
	}
	/* elastic model */
	else {
		if ( READMOD )
			readmod_elastic ( prho, ppi, pu );
		else
			model_elastic ( prho, ppi, pu );
	}

	/* check if the FD run will be stable and free of numerical dispersion */
	checkfd ( FP, prho, ppi, pu, ptaus, ptaup, peta, hc, srcpos, nsrc, recpos,
	          ntr_glob );

	/* calculate damping coefficients for CPMLs*/
	if ( ABS_TYPE==1 ) {
		PML_pro ( d_x, K_x, alpha_prime_x, a_x, b_x, d_x_half, K_x_half, alpha_prime_x_half, a_x_half, b_x_half,
		          d_y, K_y, alpha_prime_y, a_y, b_y, d_y_half, K_y_half, alpha_prime_y_half, a_y_half, b_y_half );
	}


	/*myid=0 should perform the checks above first, before proceeding */
	MPI_Barrier ( MPI_COMM_WORLD );

	/* calculate 2-D array for exponential damping of reflections
	 at the edges of the numerical mesh */
	if ( ABS_TYPE==2 ) {
		absorb ( absorb_coeff );
	}
	/* For the calculation of the material parameters beteween gridpoints
	 the have to be averaged. For this, values lying at 0 and NX+1,
	 for example, are required on the local grid. These are now copied from the
	 neighbouring grids */
	if ( L )
		matcopy ( prho, ppi, pu, ptaus, ptaup ); /* viscoelastic */
	else
		matcopy_elastic ( prho, ppi, pu ); /* elastic */

	av_mue ( pu, puipjp );
	av_rho ( prho, prip, prjp );
	if ( L )
		av_tau ( ptaus, ptausipjp );

	/* Preparing memory variables for update_s (viscoelastic) */
	if ( L )
		prepare_update_s ( etajm, etaip, peta, fipjp, pu, puipjp, ppi, ptaus,
		                   ptaup, ptausipjp, f, g, bip, bjm, cip, cjm, dip, d, e );

	MPI_Barrier ( MPI_COMM_WORLD );

	/* comunication initialisation for persistent communication */
	/*comm_ini(bufferlef_to_rig, bufferrig_to_lef, buffertop_to_bot, bufferbot_to_top,
	 req_send, req_rec);*/
	/* currently MPI_Sendrecv_replace is used! */

	time2 = MPI_Wtime();
	fprintf ( FP, "\n\n\n **************************************************\n" );
	fprintf ( FP, " *********** STARTING TIME STEPPING ***************\n" );
	fprintf ( FP, " **************************************************\n\n" );
	if ( MYID == 0 ) {
		fprintf ( FP, " real time before starting time loop: %4.2f s.\n",
		          time2 - time1 );
	}

	/*----------------------  loop over multiple shots  ------------------*/

	if ( RUN_MULTIPLE_SHOTS )
		nshots = nsrc;
	else
		nshots = 1;

	for ( ishot = 1; ishot <= nshots; ishot++ ) {

		for ( nt = 1; nt <= 8; nt++ )
			srcpos_current[nt][1] = srcpos[nt][ishot];

		if ( RUN_MULTIPLE_SHOTS ) {
			fprintf (
			    FP,
			    "\n==================================================================================\n" );
			fprintf (
			    FP,
			    "   MYID=%d *****  Starting simulation for shot %d of %d  ********** \n",
			    MYID, ishot, nshots );
			fprintf (
			    FP,
			    "==================================================================================\n\n" );
			fprintf ( FP, " Parameter for shot %d are:\n", ishot );
			fprintf (
			    FP,
			    " number\t    x\t\t    y\t\t  tshift\t    fc\t\t   amp\t	source_azimuth\n" );
			fprintf (
			    FP,
			    "    %i \t %6.2f \t %6.2f \t %6.2f \t %6.2f \t %6.2f  \t %6.2f\n\n",
			    ishot, srcpos_current[1][1], srcpos_current[2][1],
			    srcpos_current[4][1], srcpos_current[5][1],
			    srcpos_current[6][1], srcpos_current[7][1] );

			/* find this single source positions on subdomains  */
			if ( nsrc_loc > 0 )
				free_matrix ( srcpos_loc, 1, 8, 1, 1 );
			srcpos_loc = splitsrc ( srcpos_current, &nsrc_loc, 1 );
		}

		else
			srcpos_loc = splitsrc ( srcpos, &nsrc_loc, nsrc ); /* Distribute source positions on subdomains */

		MPI_Barrier ( MPI_COMM_WORLD );

		/* calculate wavelet for each source point */
		signals = wavelet ( srcpos_loc, nsrc_loc );

		/* initialize wavefield with zero */
		/* initialize wavefield with zero */

		if ( ABS_TYPE == 1 ) {
			if ( L )
				zero_PML_visc ( -nd+1,NY+nd,-nd+1,NX+nd,pvx,pvy,psxx,psyy,psxy,psi_sxx_x,psi_sxy_x,
				                psi_vxx,psi_vyx,psi_syy_y,psi_sxy_y,psi_vyy,psi_vxy,psi_vxxs,pr,pp,pq );
			else
				zero_PML_elastic ( -nd+1,NY+nd,-nd+1,NX+nd,pvx,pvy,psxx,psyy,psxy,psi_sxx_x,psi_sxy_x,
				                   psi_vxx,psi_vyx,psi_syy_y,psi_sxy_y,psi_vyy,psi_vxy,psi_vxxs );
		}



		if ( ABS_TYPE != 1 ) {
			if ( L )
				zero_visc ( -FDORDER / 2, NX + FDORDER / 2 + 1, -FDORDER / 2,
				            NY + FDORDER / 2 + 1, pvx, pvy, psxx, psyy, psxy, pr, pp,
				            pq );
			else
				zero_elastic ( -FDORDER / 2, NX + FDORDER / 2 + 1, 1 - FDORDER / 2,
				               NY + FDORDER / 2 + 1, pvx, pvy, psxx, psyy, psxy );
		}
		/* above arguments for function call have been defined differently -> minus 1 in every dimension, not quite clear why
		 old version:
		 zero_elastic(1-FDORDER/2,NX+FDORDER/2,1-FDORDER/2,NY+FDORDER/2,pvx,pvy,psxx,psyy,psxy); */

		/* Reseting lsmap to NDT for saving seismograms  */
		lsamp = NDT;

		subgrid_bounds ( 1, NX, 1, NY, gx, gy );

		/*----------------------  loop over timesteps  ------------------*/

		for ( nt = 1; nt <= NT; nt++ ) {
			  if (isnan(pvy[NY/2][NX/2])) {
		           fprintf(FP,"\n Time step: %d; pvy: %f \n",nt,pvy[NY/2][NX/2]);
       				    err(" Simulation is unstable !");}
			

			if ( ( MYID == 0 )
			        && ( ( nt + ( OUTNTIMESTEPINFO - 1 ) ) % OUTNTIMESTEPINFO ) == 0 ) {
				fprintf ( FP, "\n Computing timestep %d of %d \n", nt, NT );
				time3 = MPI_Wtime();
			}

			/* update of particle velocities ------------------------------------------------------------------------------------------*/

			update_v_interior ( 1, NX, 1, NY, gx, gy, nt, pvx, pvy, psxx, psyy, psxy, prho, prip, prjp, 
					    srcpos_loc, signals, nsrc_loc, hc );
			
			if ( FW ) {
				if ( ABS_TYPE==1 ) {
					update_v_PML ( 1, NX, 1, NY, gx, gy, nt, pvx, pvy, psxx, psyy, psxy, prip, prjp, hc, 
						       K_x, a_x, b_x, K_x_half, a_x_half, b_x_half, K_y, a_y, b_y, K_y_half, 
							a_y_half, b_y_half, psi_sxx_x, psi_syy_y, psi_sxy_y, psi_sxy_x );
				}

				if ( ABS_TYPE != 1 ) {
					update_v_abs ( 1, NX, 1, NY, gx, gy, nt, pvx, pvy, psxx, psyy, psxy, prip, prjp, absorb_coeff, hc );
				}
			}

			if ( ( MYID == 0 )
			        && ( ( nt + ( OUTNTIMESTEPINFO - 1 ) ) % OUTNTIMESTEPINFO ) == 0 ) {
				time4 = MPI_Wtime();
				time_av_v_update += ( time4 - time3 );
				fprintf ( FP, " particle velocity exchange between PEs ..." );
			}

			/* ------- exchange of particle velocities between PEs --------------*/
			
			exchange_v ( pvx, pvy, bufferlef_to_rig, bufferrig_to_lef, buffertop_to_bot, bufferbot_to_top, req_send, req_rec );

			if ( ( MYID == 0 )
			        && ( ( nt + ( OUTNTIMESTEPINFO - 1 ) ) % OUTNTIMESTEPINFO ) == 0 ) {
				time5 = MPI_Wtime();
				time_av_v_exchange += ( time5 - time4 );
				fprintf ( FP, " finished (real time: %4.3f s).\n", time5 - time4 );
			}

			/* stress update ----------------------------------------------------------------------------------------------------------*/


			if ( L ) { /* viscoelastic */
				update_s_visc_interior ( 1, NX, 1, NY, gx, gy, nt, pvx, pvy, psxx, psyy, psxy, pr, pp, pq, fipjp,
				                         f, g, bip, bjm, cip, cjm, d, e, dip, hc );
				if ( FW ) {
					if ( ABS_TYPE ==1 )
						update_s_visc_PML ( 1, NX, 1, NY, gx, gy, nt, pvx, pvy, psxx, psyy, psxy, hc, pr, pp, pq, fipjp,
						                    f, g, bip, bjm, cip, cjm, d, e, dip,K_x, a_x, b_x, K_x_half, a_x_half, b_x_half,
								    K_y, a_y, b_y, K_y_half, a_y_half, b_y_half, psi_vxx, psi_vyy, psi_vxy, psi_vyx );
					if ( ABS_TYPE !=1 )
						update_s_visc_abs ( 1, NX, 1, NY, gx,gy, nt, pvx, pvy, psxx, psyy, psxy, pr,
						                     pp, pq, ppi, fipjp, f, g, bip, bjm, cip, cjm, d, e, dip,
						                     absorb_coeff,hc );
				}


			} else { /* elastic */
				update_s_elastic_interior ( 1, NX, 1, NY, gx, gy, nt, pvx, pvy, psxx, psyy, psxy, ppi, pu, puipjp, hc );

				if ( FW ) {
					if ( ABS_TYPE ==1 )
						update_s_elastic_PML ( 1, NX, 1, NY, gx, gy, nt, pvx, pvy, psxx, psyy, psxy, ppi, pu, puipjp, hc,
						                       K_x, a_x, b_x, K_x_half, a_x_half, b_x_half, K_y, a_y, b_y, K_y_half, a_y_half, b_y_half, psi_vxx, psi_vyy, psi_vxy, psi_vyx );
					if ( ABS_TYPE !=1 )
						update_s_elastic_abs ( 1, NX, 1, NY, gx, gy, nt, pvx, pvy, psxx, psyy, psxy,
						                        ppi, pu, puipjp, absorb_coeff, hc );
				}
			}


			/* explosive source */
			if ( SOURCE_TYPE == 1 )
				psource ( nt, psxx, psyy, srcpos_loc, signals, nsrc_loc );

			if ( ( FREE_SURF ) && ( POS[2] == 0 ) ) {
				if ( L ) /* viscoelastic */
					surface ( 1, pvx, pvy, psxx, psyy, psxy, pp, pq, ppi, pu,
					          ptaup, ptaus, etajm, peta, hc, K_x, a_x, b_x, psi_vxx );
				else
					/* elastic */
					surface_elastic ( 1, gx, pvx, pvy, psxx, psyy, psxy, ppi, pu, hc, K_x, a_x, b_x, psi_vxxs );
			}

			if ( ( MYID == 0 )
			        && ( ( nt + ( OUTNTIMESTEPINFO - 1 ) ) % OUTNTIMESTEPINFO ) == 0 ) {
				time6 = MPI_Wtime();
				time_av_s_update += ( time6 - time5 );
				fprintf ( FP, " stress exchange between PEs ..." );
			}

			/* -------- stress exchange between PEs --------*/
			
			/*if ( RSG ) {
				exchange_s_rsg ( psxx, psyy, psxy, bufferlef_to_rig, bufferrig_to_lef, buffertop_to_bot, bufferbot_to_top );
			} else {*/
				exchange_s ( psxx, psyy, psxy, bufferlef_to_rig, bufferrig_to_lef, buffertop_to_bot, bufferbot_to_top, req_send, req_rec );
			

			if ( ( MYID == 0 )	&& ( ( nt + ( OUTNTIMESTEPINFO - 1 ) ) % OUTNTIMESTEPINFO ) == 0 ) {

				time7 = MPI_Wtime();
				time_av_s_exchange += ( time7 - time6 );
				fprintf ( FP, " finished (real time: %4.3f s).\n", time7 - time6 );
			}

			/* store amplitudes at receivers in section-arrays */
			if ( ( SEISMO ) && ( nt == lsamp ) && ( nt < NT ) ) {

				seismo_ssg ( lsamp, ntr, recpos_loc, sectionvx, sectionvy, sectionp, sectioncurl, sectiondiv, pvx, pvy, psxx, psyy, ppi, pu, hc );
				lsamp += NDT;
			}

			/* WRITE SNAPSHOTS TO DISK */
			if ( ( SNAP ) && ( nt == lsnap ) && ( nt <= TSNAP2 / DT ) ) {

				snap ( FP, nt, ++nsnap, pvx, pvy, psxx, psyy, pu, ppi, hc );
				lsnap = lsnap + iround ( TSNAPINC/DT );
			}

			if ( ( MYID == 0 )	&& ( ( nt + ( OUTNTIMESTEPINFO - 1 ) ) % OUTNTIMESTEPINFO ) == 0 ) {

				time8 = MPI_Wtime();
				time_av_timestep += ( time8 - time3 );
				fprintf ( FP, " total real time for timestep %d : %4.3f s.\n", nt, time8 - time3 );
			}

		}/*--------------------  End  of loop over timesteps ----------*/
		fprintf ( FP, "\n\n *********** Finish TIME STEPPING ****************\n" );
		fprintf ( FP, " **************************************************\n\n" );

		/* write seismograms to file(s) */
		if ( SEISMO ) {

			/* saves seismograms portion of each PE individually to file */
			//if (ntr> 0) saveseis(FP,sectionvx,sectionvy,sectionp,sectioncurl,sectiondiv,recpos,recpos_loc,ntr,srcpos_current,ishot,ns);

			/* merge of seismogram data from all PE and output data collectively */
			switch ( SEISMO ) {
			case 1 : /* particle velocities only */
				catseis ( sectionvx, seismo_fulldata, recswitch, ntr_glob,ns );
				if ( MYID==0 ) saveseis_glob ( FP,seismo_fulldata,recpos,recpos_loc,ntr_glob,srcpos,ishot,ns,1 );
				catseis ( sectionvy, seismo_fulldata, recswitch, ntr_glob,ns );
				if ( MYID==0 ) saveseis_glob ( FP,seismo_fulldata,recpos,recpos_loc,ntr_glob,srcpos,ishot,ns,2 );

				break;
			case 2 : /* pressure only */
				catseis ( sectionp, seismo_fulldata, recswitch, ntr_glob,ns );
				if ( MYID==0 ) saveseis_glob ( FP,seismo_fulldata,recpos,recpos_loc,ntr_glob,srcpos,ishot,ns,4 );

				break;
			case 3 : /* curl and div only */
				catseis ( sectiondiv, seismo_fulldata, recswitch, ntr_glob,ns );
				if ( MYID==0 ) saveseis_glob ( FP,seismo_fulldata,recpos,recpos_loc,ntr_glob,srcpos,ishot,ns,5 );
				catseis ( sectioncurl, seismo_fulldata, recswitch, ntr_glob,ns );
				if ( MYID==0 ) saveseis_glob ( FP,seismo_fulldata,recpos,recpos_loc,ntr_glob,srcpos,ishot,ns,6 );

				break;
			case 4 : /* everything */
				/*fprintf(FP," start merging, ntr= %d : \n",ntr_glob);
						fprintf(stdout,"Message from PE %d\n",MYID);*/
				catseis ( sectionvx, seismo_fulldata, recswitch, ntr_glob,ns );
				if ( MYID==0 ) saveseis_glob ( FP,seismo_fulldata,recpos,recpos_loc,ntr_glob,srcpos,ishot,ns,1 );
				catseis ( sectionvy, seismo_fulldata, recswitch, ntr_glob,ns );
				if ( MYID==0 ) saveseis_glob ( FP,seismo_fulldata,recpos,recpos_loc,ntr_glob,srcpos,ishot,ns,2 );
				catseis ( sectionp, seismo_fulldata, recswitch, ntr_glob,ns );
				if ( MYID==0 ) saveseis_glob ( FP,seismo_fulldata,recpos,recpos_loc,ntr_glob,srcpos,ishot,ns,4 );
				catseis ( sectiondiv, seismo_fulldata, recswitch, ntr_glob,ns );
				if ( MYID==0 ) saveseis_glob ( FP,seismo_fulldata,recpos,recpos_loc,ntr_glob,srcpos,ishot,ns,5 );
				catseis ( sectioncurl, seismo_fulldata, recswitch, ntr_glob,ns );
				if ( MYID==0 ) saveseis_glob ( FP,seismo_fulldata,recpos,recpos_loc,ntr_glob,srcpos,ishot,ns,6 );

				break;
			default :
				break;

			}
			fprintf ( FP, "\n\n" );

		}

	} /* end of loop over shots */

	/* deallocation of memory */
	free_matrix ( psxx, -nd + 1, NY + nd, -nd + 1, NX + nd );
	free_matrix ( psxy, -nd + 1, NY + nd, -nd + 1, NX + nd );
	free_matrix ( psyy, -nd + 1, NY + nd, -nd + 1, NX + nd );
	free_matrix ( pvx, -nd + 1, NY + nd, -nd + 1, NX + nd );
	free_matrix ( pvy, -nd + 1, NY + nd, -nd + 1, NX + nd );
	free_matrix ( prho, -nd + 1, NY + nd, -nd + 1, NX + nd );
	free_matrix ( prip, -nd + 1, NY + nd, -nd + 1, NX + nd );
	free_matrix ( prjp, -nd + 1, NY + nd, -nd + 1, NX + nd );
	free_matrix ( ppi, -nd + 1, NY + nd, -nd + 1, NX + nd );
	free_matrix ( pu, -nd + 1, NY + nd, -nd + 1, NX + nd );
	free_matrix ( puipjp, -nd + 1, NY + nd, -nd + 1, NX + nd );
	free_matrix ( absorb_coeff, 1, NY, 1, NX );

	free_ivector ( gx,1,4 );
	free_ivector ( gy,1,4 );

	if ( L ) {
		free_f3tensor ( pr, -nd + 1, NY + nd, -nd + 1, NX + nd, 1, L );
		free_f3tensor ( pp, -nd + 1, NY + nd, -nd + 1, NX + nd, 1, L );
		free_f3tensor ( pq, -nd + 1, NY + nd, -nd + 1, NX + nd, 1, L );
		free_matrix ( ptaus, -nd + 1, NY + nd, -nd + 1, NX + nd );
		free_matrix ( ptausipjp, -nd + 1, NY + nd, -nd + 1, NX + nd );
		free_matrix ( ptaup, -nd + 1, NY + nd, -nd + 1, NX + nd );
		free_vector ( peta, 1, L );
		free_vector ( etaip, 1, L );
		free_vector ( etajm, 1, L );
		free_vector ( bip, 1, L );
		free_vector ( bjm, 1, L );
		free_vector ( cip, 1, L );
		free_vector ( cjm, 1, L );
		free_matrix ( f, -nd + 1, NY + nd, -nd + 1, NX + nd );
		free_matrix ( g, -nd + 1, NY + nd, -nd + 1, NX + nd );
		free_matrix ( fipjp, -nd + 1, NY + nd, -nd + 1, NX + nd );
		free_f3tensor ( dip, -nd + 1, NY + nd, -nd + 1, NX + nd, 1, L );
		free_f3tensor ( d, -nd + 1, NY + nd, -nd + 1, NX + nd, 1, L );
		free_f3tensor ( e, -nd + 1, NY + nd, -nd + 1, NX + nd, 1, L );
	}

	/*if ( RSG ) {
		free_matrix ( bufferlef_to_rig, 0, NY + 1, 1, fdo3 );
		free_matrix ( bufferrig_to_lef, 0, NY + 1, 1, fdo3 );
		free_matrix ( buffertop_to_bot, 1, NX, 1, fdo3 );
		free_matrix ( bufferbot_to_top, 1, NX, 1, fdo3 );
	} else {*/
		free_matrix ( bufferlef_to_rig, 1, NY, 1, fdo3 );
		free_matrix ( bufferrig_to_lef, 1, NY, 1, fdo3 );
		free_matrix ( buffertop_to_bot, 1, NX, 1, fdo3 );
		free_matrix ( bufferbot_to_top, 1, NX, 1, fdo3 );
	

	if ( nsrc_loc > 0 ) {
		free_matrix ( signals, 1, nsrc_loc, 1, NT );
		free_matrix ( srcpos_loc, 1, 8, 1, nsrc_loc );
	}

	if ( ABS_TYPE==1 ) {

		free_vector ( d_x,1,2*FW );
		free_vector ( K_x,1,2*FW );
		free_vector ( alpha_prime_x,1,2*FW );
		free_vector ( a_x,1,2*FW );
		free_vector ( b_x,1,2*FW );

		free_vector ( d_x_half,1,2*FW );
		free_vector ( K_x_half,1,2*FW );
		free_vector ( alpha_prime_x_half,1,2*FW );
		free_vector ( a_x_half,1,2*FW );
		free_vector ( b_x_half,1,2*FW );

		free_vector ( d_y,1,2*FW );
		free_vector ( K_y,1,2*FW );
		free_vector ( alpha_prime_y,1,2*FW );
		free_vector ( a_y,1,2*FW );
		free_vector ( b_y,1,2*FW );

		free_vector ( d_y_half,1,2*FW );
		free_vector ( K_y_half,1,2*FW );
		free_vector ( alpha_prime_y_half,1,2*FW );
		free_vector ( a_y_half,1,2*FW );
		free_vector ( b_y_half,1,2*FW );

		free_matrix ( psi_sxx_x,1,NY,1,2*FW );
		free_matrix ( psi_syy_y,1,2*FW,1,NX );
		free_matrix ( psi_sxy_x,1,NY,1,2*FW );
		free_matrix ( psi_sxy_y,1,2*FW,1,NX );
		free_matrix ( psi_vxx,1,NY,1,2*FW );
		free_matrix ( psi_vyy,1,2*FW,1,NX );
		free_matrix ( psi_vxy,1,2*FW,1,NX );
		free_matrix ( psi_vyx,1,NY,1,2*FW );

	}



	if ( SEISMO )
		free_imatrix ( recpos, 1, 3, 1, ntr_glob );

	/* free memory for global source positions */
	free_matrix ( srcpos, 1, 8, 1, nsrc );

	if ( ( ntr > 0 ) && ( SEISMO ) ) {

		free_matrix ( seismo_fulldata,1,ntr_glob,1,ns );
		free_imatrix ( recpos_loc, 1, 3, 1, ntr );
		switch ( SEISMO ) {
		case 1: /* particle velocities only */
			free_matrix ( sectionvx, 1, ntr, 1, ns );
			free_matrix ( sectionvy, 1, ntr, 1, ns );
			break;
		case 2: /* pressure only */
			free_matrix ( sectionp, 1, ntr, 1, ns );
			break;
		case 3: /* curl and div only */
			free_matrix ( sectioncurl, 1, ntr, 1, ns );
			free_matrix ( sectiondiv, 1, ntr, 1, ns );
			break;
		case 4: /* everything */
			free_matrix ( sectionvx, 1, ntr, 1, ns );
			free_matrix ( sectionvy, 1, ntr, 1, ns );
			free_matrix ( sectionp, 1, ntr, 1, ns );
			free_matrix ( sectioncurl, 1, ntr, 1, ns );
			free_matrix ( sectiondiv, 1, ntr, 1, ns );
			break;
		}

	}

	/* de-allocate buffer for messages */
	MPI_Buffer_detach ( buff_addr, &buffsize );

	/* merge snapshot files created by the PEs into one file */
	/* if ((SNAP) && (MYID==0)){
	 snapmerge(nsnap);
	 }
	 */

	MPI_Barrier ( MPI_COMM_WORLD );

	if ( MYID == 0 ) {
		fprintf ( FP, "\n **Info from main (written by PE %d): \n", MYID );

		time_av_v_update = time_av_v_update / ( double ) NT;
		time_av_s_update = time_av_s_update / ( double ) NT;
		time_av_v_exchange = time_av_v_exchange / ( double ) NT;
		time_av_s_exchange = time_av_s_exchange / ( double ) NT;
		time_av_timestep = time_av_timestep / ( double ) NT;
		fprintf ( FP, " Average times for \n" );
		fprintf ( FP, "   velocity update:  \t %5.6f seconds  \n",
		          time_av_v_update );
		fprintf ( FP, "   stress update:  \t %5.6f seconds  \n",
		          time_av_s_update );
		fprintf ( FP, "   velocity exchange:  \t %5.6f seconds  \n",
		          time_av_v_exchange );
		fprintf ( FP, "   stress exchange:  \t %5.6f seconds  \n",
		          time_av_s_exchange );
		fprintf ( FP, "   timestep:  \t\t %5.6f seconds  \n\n", time_av_timestep );

		fprintf ( FP, " CPU time of program per PE: %li seconds.\n",
		          clock() / CLOCKS_PER_SEC );
		time8 = MPI_Wtime();
		fprintf ( FP, " Total real time of program: %4.3f seconds.\n\n",
		          time8 - time1 );
		fprintf ( FP," ******************************************************\n" );
		fprintf ( FP," **************** SOFI2D has finished *****************\n" );
		fprintf ( FP," ******************************************************\n\n" );

	}

	fclose ( FP );
	MPI_Finalize();
	return 0;

} /*main*/