void cosmo_init_particles( unsigned seed )
{
fftwf_real *data = new fftwf_real[ nres * (nres+2) ];
fftwf_complex *cdata = reinterpret_cast<fftwf_complex*>(data);
fftwf_real *data2 = new fftwf_real[ nres * (nres+2) ];
fftwf_complex *cdata2 = reinterpret_cast<fftwf_complex*>(data2);
gsl_rng *RNG = gsl_rng_alloc( gsl_rng_mt19937 );
gsl_rng_set( RNG, seed );
fftwf_plan plan, iplan, plan2, iplan2;
plan = fftwf_plan_dft_r2c_2d( nres, nres, data, cdata, FFTW_MEASURE ),
iplan = fftwf_plan_dft_c2r_2d( nres, nres, cdata, data, FFTW_MEASURE );
plan2 = fftwf_plan_dft_r2c_2d( nres, nres, data2, cdata2, FFTW_MEASURE ),
iplan2 = fftwf_plan_dft_c2r_2d( nres, nres, cdata2, data2, FFTW_MEASURE );
/////////////////////////////////
int nresp = nres/2+1;
float kfac = 2.0*M_PI/boxlength;
float gaussran1, gaussran2;
float fftnorm = 1.0f / (float)nres * (2.0f*M_PI/boxlength);
for( int i=0; i<nres; ++i )
for( int j=0; j<nres; ++j )
{
int idx = i*(nres+2)+j;
data[idx] = gsl_ran_ugaussian_ratio_method( RNG ) / nres;
}
fftwf_execute( plan );
/////////////////////////////////
for( int i=0; i<nres; ++i )
for( int j=0; j<nresp; ++j )
{
float kx = i>=nresp? (float)(i-nres)*kfac : (float)i*kfac;
float ky = (float)j*kfac;
float kk = sqrtf(kx*kx+ky*ky);
int idx = i*nresp+j;
float ampk = cosmo_get_amp_k( kk ); //*sqrtf(kk);
if( kk >= nresp*kfac )
ampk = 0.0;
cdata[idx][0] *= ampk * fftnorm;
cdata[idx][1] *= ampk * fftnorm;
}
// insert code to make random numbers independent of resolution (have rectangle outliens)
float dx = boxlength / nres;
float vfact = ComputeVFact( 1.0f/(1.0f+g_zstart));
/////////////////////////////////
// generate x-component
for( int i=0; i<nres; ++i )
for( int j=0; j<nresp; ++j )
{
float kx = i>=nresp? (float)(i-nres)*kfac : (float)i*kfac;
float ky = (float)j*kfac;
float kk = sqrtf(kx*kx+ky*ky);
int idx = i*nresp+j; // (a+ib) * ik = iak -bk
cdata2[idx][0] = kx/kk/kk * cdata[idx][1];
cdata2[idx][1] = -kx/kk/kk * cdata[idx][0];
}
cdata2[0][0] = 0.0f;
cdata2[0][1] = 0.0f;
fftwf_execute( iplan2 );
for( int i=0; i<nres; ++i )
for( int j=0; j<nres; ++j )
{
int idx = i*(nres+2)+j;
int ii = i*nres+j;
P[ii].x = (float)i*dx + data2[idx];
P[ii].vx = data2[idx] * vfact;
P[ii].id = ii;
P[ii].acc[0] = 0.0f;
}
/////////////////////////////////
// generate y-component
for( int i=0; i<nres; ++i )
for( int j=0; j<nresp; ++j )
{
float kx = i>=nresp? (float)(i-nres)*kfac : (float)i*kfac;
float ky = (float)j*kfac;
float kk = sqrtf(kx*kx+ky*ky);
int idx = i*nresp+j;
cdata2[idx][0] = ky/kk/kk * cdata[idx][1];
cdata2[idx][1] = -ky/kk/kk * cdata[idx][0];
}
cdata2[0][0] = 0.0f;
cdata2[0][1] = 0.0f;
fftwf_execute( iplan2 );
for( int i=0; i<nres; ++i )
for( int j=0; j<nres; ++j )
{
int idx = i*(nres+2)+j;
int ii = i*nres+j;
P[ii].y = (float)j*dx + data2[idx];
P[ii].vy = data2[idx] * vfact;
P[ii].acc[1] = 0.0f;
}
/////////////////////////////////
delete[] data;
delete[] data2;
fftwf_destroy_plan(plan);
fftwf_destroy_plan(iplan);
fftwf_destroy_plan(plan2);
fftwf_destroy_plan(iplan2);
gsl_rng_free( RNG );
}
double
test_ugaussian_ratio_method (void)
{
return gsl_ran_ugaussian_ratio_method (r_global);
}
