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init.c
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Sat, May 25, 05:21

init.c
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#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <mpi.h>
#include "allvars.h"
#include "proto.h"
/*! \file init.c
* \brief Code for initialisation of a simulation from initial conditions
*/
/*! This function reads the initial conditions, and allocates storage for the
* tree. Various variables of the particle data are initialised and An intial
* domain decomposition is performed. If SPH particles are present, the inial
* SPH smoothing lengths are determined.
*/
void init(void)
{
int i, j;
double a3;
All.Time = All.TimeBegin;
switch (All.ICFormat)
{
case 1:
#if (MAKEGLASS > 1)
seed_glass();
#else
read_ic(All.InitCondFile);
#endif
break;
case 2:
case 3:
read_ic(All.InitCondFile);
break;
default:
if(ThisTask == 0)
printf("ICFormat=%d not supported.\n", All.ICFormat);
endrun(0);
}
All.Time = All.TimeBegin;
All.Ti_Current = 0;
if(All.ComovingIntegrationOn)
{
All.Timebase_interval = (log(All.TimeMax) - log(All.TimeBegin)) / TIMEBASE;
a3 = All.Time * All.Time * All.Time;
}
else
{
All.Timebase_interval = (All.TimeMax - All.TimeBegin) / TIMEBASE;
a3 = 1;
}
set_softenings();
All.NumCurrentTiStep = 0; /* setup some counters */
All.SnapshotFileCount = 0;
if(RestartFlag == 2)
All.SnapshotFileCount = atoi(All.InitCondFile + strlen(All.InitCondFile) - 3) + 1;
All.TotNumOfForces = 0;
All.NumForcesSinceLastDomainDecomp = 0;
if(All.ComovingIntegrationOn)
if(All.PeriodicBoundariesOn == 1)
check_omega();
All.TimeLastStatistics = All.TimeBegin - All.TimeBetStatistics;
if(All.ComovingIntegrationOn) /* change to new velocity variable */
{
for(i = 0; i < NumPart; i++)
for(j = 0; j < 3; j++)
P[i].Vel[j] *= sqrt(All.Time) * All.Time;
}
for(i = 0; i < NumPart; i++) /* start-up initialization */
{
for(j = 0; j < 3; j++)
P[i].GravAccel[j] = 0;
#ifdef PMGRID
for(j = 0; j < 3; j++)
P[i].GravPM[j] = 0;
#endif
P[i].Ti_endstep = 0;
P[i].Ti_begstep = 0;
P[i].OldAcc = 0;
P[i].GravCost = 1;
P[i].Potential = 0;
}
#ifdef PMGRID
All.PM_Ti_endstep = All.PM_Ti_begstep = 0;
#endif
#ifdef FLEXSTEPS
All.PresentMinStep = TIMEBASE;
for(i = 0; i < NumPart; i++) /* start-up initialization */
{
P[i].FlexStepGrp = (int) (TIMEBASE * get_random_number(P[i].ID));
}
#endif
for(i = 0; i < N_gas; i++) /* initialize sph_properties */
{
for(j = 0; j < 3; j++)
{
SphP[i].VelPred[j] = P[i].Vel[j];
SphP[i].HydroAccel[j] = 0;
}
SphP[i].DtEntropy = 0;
if(RestartFlag == 0)
{
SphP[i].Hsml = 0;
SphP[i].Density = -1;
}
}
ngb_treeallocate(MAX_NGB);
force_treeallocate(All.TreeAllocFactor * All.MaxPart, All.MaxPart);
All.NumForcesSinceLastDomainDecomp = 1 + All.TotNumPart * All.TreeDomainUpdateFrequency;
Flag_FullStep = 1; /* to ensure that Peano-Hilber order is done */
domain_Decomposition(); /* do initial domain decomposition (gives equal numbers of particles) */
ngb_treebuild(); /* will build tree */
setup_smoothinglengths();
TreeReconstructFlag = 1;
/* at this point, the entropy variable normally contains the
* internal energy, read in from the initial conditions file, unless the file
* explicitly signals that the initial conditions contain the entropy directly.
* Once the density has been computed, we can convert thermal energy to entropy.
*/
#ifndef ISOTHERM_EQS
if(header.flag_entropy_instead_u == 0)
for(i = 0; i < N_gas; i++)
SphP[i].Entropy = GAMMA_MINUS1 * SphP[i].Entropy / pow(SphP[i].Density / a3, GAMMA_MINUS1);
#endif
}
/*! This routine computes the mass content of the box and compares it to the
* specified value of Omega-matter. If discrepant, the run is terminated.
*/
void check_omega(void)
{
double mass = 0, masstot, omega;
int i;
for(i = 0; i < NumPart; i++)
mass += P[i].Mass;
MPI_Allreduce(&mass, &masstot, 1, MPI_DOUBLE, MPI_SUM, MPI_COMM_WORLD);
omega =
masstot / (All.BoxSize * All.BoxSize * All.BoxSize) / (3 * All.Hubble * All.Hubble / (8 * M_PI * All.G));
if(fabs(omega - All.Omega0) > 1.0e-3)
{
if(ThisTask == 0)
{
printf("\n\nI've found something odd!\n");
printf
("The mass content accounts only for Omega=%g,\nbut you specified Omega=%g in the parameterfile.\n",
omega, All.Omega0);
printf("\nI better stop.\n");
fflush(stdout);
}
endrun(1);
}
}
/*! This function is used to find an initial smoothing length for each SPH
* particle. It guarantees that the number of neighbours will be between
* desired_ngb-MAXDEV and desired_ngb+MAXDEV. For simplicity, a first guess
* of the smoothing length is provided to the function density(), which will
* then iterate if needed to find the right smoothing length.
*/
void setup_smoothinglengths(void)
{
int i, no, p;
if(RestartFlag == 0)
{
for(i = 0; i < N_gas; i++)
{
no = Father[i];
while(10 * All.DesNumNgb * P[i].Mass > Nodes[no].u.d.mass)
{
p = Nodes[no].u.d.father;
if(p < 0)
break;
no = p;
}
#ifndef TWODIMS
SphP[i].Hsml =
pow(3.0 / (4 * M_PI) * All.DesNumNgb * P[i].Mass / Nodes[no].u.d.mass, 1.0 / 3) * Nodes[no].len;
#else
SphP[i].Hsml =
pow(1.0 / (M_PI) * All.DesNumNgb * P[i].Mass / Nodes[no].u.d.mass, 1.0 / 2) * Nodes[no].len;
#endif
}
}
density();
}
#ifdef PY_INTERFACE
/*! This function is used to find an initial smoothing length for each SPH
* particle. It guarantees that the number of neighbours will be between
* desired_ngb-MAXDEV and desired_ngb+MAXDEV. For simplicity, a first guess
* of the smoothing length is provided to the function density(), which will
* then iterate if needed to find the right smoothing length.
*/
void setup_smoothinglengths_sub(void)
{
/* before, we can not use the tree, as Q particles do not belong to them... */
density_sub();
}
#endif
/*! If the code is run in glass-making mode, this function populates the
* simulation box with a Poisson sample of particles.
*/
#if (MAKEGLASS > 1)
void seed_glass(void)
{
int i, k, n_for_this_task;
double Range[3], LowerBound[3];
double drandom, partmass;
long long IDstart;
All.TotNumPart = MAKEGLASS;
partmass = All.Omega0 * (3 * All.Hubble * All.Hubble / (8 * M_PI * All.G))
* (All.BoxSize * All.BoxSize * All.BoxSize) / All.TotNumPart;
All.MaxPart = All.PartAllocFactor * (All.TotNumPart / NTask); /* sets the maximum number of particles that may */
allocate_memory();
header.npartTotal[1] = All.TotNumPart;
header.mass[1] = partmass;
if(ThisTask == 0)
{
printf("\nGlass initialising\nPartMass= %g\n", partmass);
printf("TotNumPart= %d%09d\n\n",
(int) (All.TotNumPart / 1000000000), (int) (All.TotNumPart % 1000000000));
}
/* set the number of particles assigned locally to this task */
n_for_this_task = All.TotNumPart / NTask;
if(ThisTask == NTask - 1)
n_for_this_task = All.TotNumPart - (NTask - 1) * n_for_this_task;
NumPart = 0;
IDstart = 1 + (All.TotNumPart / NTask) * ThisTask;
/* split the temporal domain into Ntask slabs in z-direction */
Range[0] = Range[1] = All.BoxSize;
Range[2] = All.BoxSize / NTask;
LowerBound[0] = LowerBound[1] = 0;
LowerBound[2] = ThisTask * Range[2];
srand48(ThisTask);
for(i = 0; i < n_for_this_task; i++)
{
for(k = 0; k < 3; k++)
{
drandom = drand48();
P[i].Pos[k] = LowerBound[k] + Range[k] * drandom;
P[i].Vel[k] = 0;
}
P[i].Mass = partmass;
P[i].Type = 1;
P[i].ID = IDstart + i;
NumPart++;
}
}
#endif

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