/**
* The main program.
*
* \param argc The number of arguments
* \param argv An array containing the arguments as C-strings
*
* \return Exit code
*
* \author Jens Keiner
*/
int main (int argc, char **argv)
{
int T;
int N;
int M;
int M2;
int t; /* Index variable for testcases */
nfsft_plan plan; /* NFSFT plan */
nfsft_plan plan2; /* NFSFT plan */
solver_plan_complex iplan; /* NFSFT plan */
int j; /* */
int k; /* */
int m; /* */
int use_nfsft; /* */
int use_nfft; /* */
int use_fpt; /* */
int cutoff; /**< The current NFFT cut-off parameter */
double threshold; /**< The current NFSFT threshold parameter */
double re;
double im;
double a;
double *scratch;
double xs;
double *ys;
double *temp;
double _Complex *temp2;
int qlength;
double *qweights;
fftw_plan fplan;
fpt_set set;
int npt;
int npt_exp;
double *alpha, *beta, *gamma;
/* Read the number of testcases. */
fscanf(stdin,"testcases=%d\n",&T);
fprintf(stderr,"%d\n",T);
/* Process each testcase. */
for (t = 0; t < T; t++)
{
/* Check if the fast transform shall be used. */
fscanf(stdin,"nfsft=%d\n",&use_nfsft);
fprintf(stderr,"%d\n",use_nfsft);
if (use_nfsft != NO)
{
/* Check if the NFFT shall be used. */
fscanf(stdin,"nfft=%d\n",&use_nfft);
fprintf(stderr,"%d\n",use_nfsft);
if (use_nfft != NO)
{
/* Read the cut-off parameter. */
fscanf(stdin,"cutoff=%d\n",&cutoff);
fprintf(stderr,"%d\n",cutoff);
}
else
{
/* TODO remove this */
/* Initialize unused variable with dummy value. */
cutoff = 1;
}
/* Check if the fast polynomial transform shall be used. */
fscanf(stdin,"fpt=%d\n",&use_fpt);
fprintf(stderr,"%d\n",use_fpt);
if (use_fpt != NO)
{
/* Read the NFSFT threshold parameter. */
fscanf(stdin,"threshold=%lf\n",&threshold);
fprintf(stderr,"%lf\n",threshold);
}
else
{
/* TODO remove this */
/* Initialize unused variable with dummy value. */
threshold = 1000.0;
}
}
else
{
/* TODO remove this */
/* Set dummy values. */
use_nfft = NO;
use_fpt = NO;
cutoff = 3;
threshold = 1000.0;
}
/* Read the bandwidth. */
fscanf(stdin,"bandwidth=%d\n",&N);
fprintf(stderr,"%d\n",N);
/* Do precomputation. */
nfsft_precompute(N,threshold,
((use_nfsft==NO)?(NFSFT_NO_FAST_ALGORITHM):(0U/*NFSFT_NO_DIRECT_ALGORITHM*/)), 0U);
/* Read the number of nodes. */
fscanf(stdin,"nodes=%d\n",&M);
fprintf(stderr,"%d\n",M);
/* */
if ((N+1)*(N+1) > M)
{
X(next_power_of_2_exp)(N, &npt, &npt_exp);
fprintf(stderr, "npt = %d, npt_exp = %d\n", npt, npt_exp);
fprintf(stderr,"Optimal interpolation!\n");
scratch = (double*) nfft_malloc(4*sizeof(double));
ys = (double*) nfft_malloc((N+1)*sizeof(double));
temp = (double*) nfft_malloc((2*N+1)*sizeof(double));
temp2 = (double _Complex*) nfft_malloc((N+1)*sizeof(double _Complex));
a = 0.0;
for (j = 0; j <= N; j++)
{
xs = 2.0 + (2.0*j)/(N+1);
ys[j] = (2.0-((j == 0)?(1.0):(0.0)))*4.0*nfft_bspline(4,xs,scratch);
//fprintf(stdout,"%3d: g(%le) = %le\n",j,xs,ys[j]);
a += ys[j];
}
//fprintf(stdout,"a = %le\n",a);
for (j = 0; j <= N; j++)
{
ys[j] *= 1.0/a;
}
qlength = 2*N+1;
qweights = (double*) nfft_malloc(qlength*sizeof(double));
fplan = fftw_plan_r2r_1d(N+1, qweights, qweights, FFTW_REDFT00, 0U);
for (j = 0; j < N+1; j++)
{
qweights[j] = -2.0/(4*j*j-1);
}
fftw_execute(fplan);
qweights[0] *= 0.5;
for (j = 0; j < N+1; j++)
{
qweights[j] *= 1.0/(2.0*N+1.0);
qweights[2*N+1-1-j] = qweights[j];
}
fplan = fftw_plan_r2r_1d(2*N+1, temp, temp, FFTW_REDFT00, 0U);
for (j = 0; j <= N; j++)
{
temp[j] = ((j==0 || j == 2*N)?(1.0):(0.5))*ys[j];
}
for (j = N+1; j < 2*N+1; j++)
{
temp[j] = 0.0;
}
fftw_execute(fplan);
for (j = 0; j < 2*N+1; j++)
{
temp[j] *= qweights[j];
}
fftw_execute(fplan);
for (j = 0; j < 2*N+1; j++)
{
temp[j] *= ((j==0 || j == 2*N)?(1.0):(0.5));
if (j <= N)
{
temp2[j] = temp[j];
}
}
set = fpt_init(1, npt_exp, 0U);
alpha = (double*) nfft_malloc((N+2)*sizeof(double));
beta = (double*) nfft_malloc((N+2)*sizeof(double));
gamma = (double*) nfft_malloc((N+2)*sizeof(double));
alpha_al_row(alpha, N, 0);
beta_al_row(beta, N, 0);
gamma_al_row(gamma, N, 0);
fpt_precompute(set, 0, alpha, beta, gamma, 0, 1000.0);
fpt_transposed(set,0, temp2, temp2, N, 0U);
fpt_finalize(set);
nfft_free(alpha);
nfft_free(beta);
nfft_free(gamma);
fftw_destroy_plan(fplan);
nfft_free(scratch);
nfft_free(qweights);
nfft_free(ys);
nfft_free(temp);
}
/* Init transform plans. */
nfsft_init_guru(&plan, N, M,
((use_nfft!=0)?(0U):(NFSFT_USE_NDFT)) |
((use_fpt!=0)?(0U):(NFSFT_USE_DPT)) | NFSFT_MALLOC_F | NFSFT_MALLOC_X |
NFSFT_MALLOC_F_HAT | NFSFT_NORMALIZED | NFSFT_ZERO_F_HAT,
PRE_PHI_HUT | PRE_PSI | FFTW_INIT |
FFT_OUT_OF_PLACE,
cutoff);
if ((N+1)*(N+1) > M)
{
solver_init_advanced_complex(&iplan, (nfft_mv_plan_complex*)(&plan), CGNE | PRECOMPUTE_DAMP);
}
else
{
solver_init_advanced_complex(&iplan, (nfft_mv_plan_complex*)(&plan), CGNR | PRECOMPUTE_WEIGHT | PRECOMPUTE_DAMP);
}
/* Read the nodes and function values. */
for (j = 0; j < M; j++)
{
fscanf(stdin,"%le %le %le %le\n",&plan.x[2*j+1],&plan.x[2*j],&re,&im);
plan.x[2*j+1] = plan.x[2*j+1]/(2.0*PI);
plan.x[2*j] = plan.x[2*j]/(2.0*PI);
if (plan.x[2*j] >= 0.5)
{
plan.x[2*j] = plan.x[2*j] - 1;
}
iplan.y[j] = re + _Complex_I * im;
fprintf(stderr,"%le %le %le %le\n",plan.x[2*j+1],plan.x[2*j],
creal(iplan.y[j]),cimag(iplan.y[j]));
}
/* Read the number of nodes. */
fscanf(stdin,"nodes_eval=%d\n",&M2);
fprintf(stderr,"%d\n",M2);
/* Init transform plans. */
nfsft_init_guru(&plan2, N, M2,
((use_nfft!=0)?(0U):(NFSFT_USE_NDFT)) |
((use_fpt!=0)?(0U):(NFSFT_USE_DPT)) | NFSFT_MALLOC_F | NFSFT_MALLOC_X |
NFSFT_MALLOC_F_HAT | NFSFT_NORMALIZED | NFSFT_ZERO_F_HAT,
PRE_PHI_HUT | PRE_PSI | FFTW_INIT |
FFT_OUT_OF_PLACE,
cutoff);
/* Read the nodes and function values. */
for (j = 0; j < M2; j++)
{
fscanf(stdin,"%le %le\n",&plan2.x[2*j+1],&plan2.x[2*j]);
plan2.x[2*j+1] = plan2.x[2*j+1]/(2.0*PI);
plan2.x[2*j] = plan2.x[2*j]/(2.0*PI);
if (plan2.x[2*j] >= 0.5)
{
plan2.x[2*j] = plan2.x[2*j] - 1;
}
fprintf(stderr,"%le %le\n",plan2.x[2*j+1],plan2.x[2*j]);
}
nfsft_precompute_x(&plan);
nfsft_precompute_x(&plan2);
/* Frequency weights. */
if ((N+1)*(N+1) > M)
{
/* Compute Voronoi weights. */
//nfft_voronoi_weights_S2(iplan.w, plan.x, M);
/* Print out Voronoi weights. */
/*a = 0.0;
for (j = 0; j < plan.M_total; j++)
{
fprintf(stderr,"%le\n",iplan.w[j]);
a += iplan.w[j];
}
fprintf(stderr,"sum = %le\n",a);*/
for (j = 0; j < plan.N_total; j++)
{
iplan.w_hat[j] = 0.0;
}
for (k = 0; k <= N; k++)
{
for (j = -k; j <= k; j++)
{
iplan.w_hat[NFSFT_INDEX(k,j,&plan)] = 1.0/(pow(k+1.0,2.0)); /*temp2[j]*/;
}
}
}
else
{
for (j = 0; j < plan.N_total; j++)
{
iplan.w_hat[j] = 0.0;
}
for (k = 0; k <= N; k++)
{
for (j = -k; j <= k; j++)
{
iplan.w_hat[NFSFT_INDEX(k,j,&plan)] = 1/(pow(k+1.0,2.5));
}
}
/* Compute Voronoi weights. */
nfft_voronoi_weights_S2(iplan.w, plan.x, M);
/* Print out Voronoi weights. */
a = 0.0;
for (j = 0; j < plan.M_total; j++)
{
fprintf(stderr,"%le\n",iplan.w[j]);
a += iplan.w[j];
}
fprintf(stderr,"sum = %le\n",a);
}
fprintf(stderr, "N_total = %d\n", plan.N_total);
fprintf(stderr, "M_total = %d\n", plan.M_total);
/* init some guess */
for (k = 0; k < plan.N_total; k++)
{
iplan.f_hat_iter[k] = 0.0;
}
/* inverse trafo */
solver_before_loop_complex(&iplan);
/*for (k = 0; k < plan.M_total; k++)
{
printf("%le %le\n",creal(iplan.r_iter[k]),cimag(iplan.r_iter[k]));
}*/
for (m = 0; m < 29; m++)
{
fprintf(stderr,"Residual ||r||=%e,\n",sqrt(iplan.dot_r_iter));
solver_loop_one_step_complex(&iplan);
}
/*NFFT_SWAP_complex(iplan.f_hat_iter, plan.f_hat);
nfsft_trafo(&plan);
NFFT_SWAP_complex(iplan.f_hat_iter, plan.f_hat);
a = 0.0;
b = 0.0;
for (k = 0; k < plan.M_total; k++)
{
printf("%le %le %le\n",cabs(iplan.y[k]),cabs(plan.f[k]),
cabs(iplan.y[k]-plan.f[k]));
a += cabs(iplan.y[k]-plan.f[k])*cabs(iplan.y[k]-plan.f[k]);
b += cabs(iplan.y[k])*cabs(iplan.y[k]);
}
fprintf(stderr,"relative error in 2-norm: %le\n",a/b);*/
NFFT_SWAP_complex(iplan.f_hat_iter, plan2.f_hat);
nfsft_trafo(&plan2);
NFFT_SWAP_complex(iplan.f_hat_iter, plan2.f_hat);
for (k = 0; k < plan2.M_total; k++)
{
fprintf(stdout,"%le\n",cabs(plan2.f[k]));
}
solver_finalize_complex(&iplan);
nfsft_finalize(&plan);
nfsft_finalize(&plan2);
/* Delete precomputed data. */
nfsft_forget();
if ((N+1)*(N+1) > M)
{
nfft_free(temp2);
}
} /* Process each testcase. */
/* Return exit code for successful run. */
return EXIT_SUCCESS;
}
int main(void)
{
/* This example shows the use of the fast polynomial transform to evaluate a
* finite expansion in Legendre polynomials,
*
* f(x) = a_0 P_0(x) + a_1 P_1(x) + ... + a_N P_N(x) (1)
*
* at the Chebyshev nodes x_j = cos(j*pi/N), j=0,1,...,N. */
const int N = 8;
/* An fpt_set is a data structure that contains precomputed data for a number
* of different polynomial transforms. Here, we need only one transform. the
* second parameter (t) is the exponent of the maximum transform size desired
* (2^t), i.e., t = 3 means that N in (1) can be at most N = 8. */
fpt_set set = fpt_init(1,lrint(ceil(log2((double)N))),0U);
/* Three-term recurrence coefficients for Legendre polynomials */
double *alpha = malloc((N+2)*sizeof(double)),
*beta = malloc((N+2)*sizeof(double)),
*gamma = malloc((N+2)*sizeof(double));
/* alpha[0] and beta[0] are not referenced. */
alpha[0] = beta[0] = 0.0;
/* gamma[0] contains the value of P_0(x) (which is a constant). */
gamma[0] = 1.0;
/* Actual three-term recurrence coefficients for Legendre polynomials */
{
int k;
for (k = 0; k <= N; k++)
{
alpha[k+1] = ((double)(2*k+1))/((double)(k+1));
beta[k+1] = 0.0;
gamma[k+1] = -((double)(k))/((double)(k+1));
}
}
printf(
"Computing a fast polynomial transform (FPT) and a fast discrete cosine \n"
"transform (DCT) to evaluate\n\n"
" f_j = a_0 P_0(x_j) + a_1 P_1(x_j) + ... + a_N P_N(x_j), j=0,1,...,N,\n\n"
"with N=%d, x_j = cos(j*pi/N), j=0,1,...N, the Chebyshev nodes, a_k,\n"
"k=0,1,...,N, random Fourier coefficients in [-1,1]x[-1,1]*I, and P_k,\n"
"k=0,1,...,N, the Legendre polynomials.",N
);
/* Random seed, makes things reproducible. */
nfft_srand48(314);
/* The function fpt_repcompute actually does the precomputation for a single
* transform. It needs arrays alpha, beta, and gamma, containing the three-
* term recurrence coefficients, here of the Legendre polynomials. The format
* is explained above. The sixth parameter (k_start) is where the index in the
* linear combination (1) starts, here k_start=0. The seventh parameter
* (kappa) is the threshold which has an influence on the accuracy of the fast
* polynomial transform. Usually, kappa = 1000 is a good choice. */
fpt_precompute(set,0,alpha,beta,gamma,0,1000.0);
{
/* Arrays for Fourier coefficients and function values. */
double _Complex *a = malloc((N+1)*sizeof(double _Complex));
double _Complex *b = malloc((N+1)*sizeof(double _Complex));
double *f = malloc((N+1)*sizeof(double _Complex));
/* Plan for discrete cosine transform */
const int NP1 = N + 1;
fftw_r2r_kind kind = FFTW_REDFT00;
fftw_plan p = fftw_plan_many_r2r(1, &NP1, 1, (double*)b, NULL, 2, 1,
(double*)f, NULL, 1, 1, &kind, 0U);
/* random Fourier coefficients */
{
int k;
printf("\n2) Random Fourier coefficients a_k, k=0,1,...,N:\n");
for (k = 0; k <= N; k++)
{
a[k] = 2.0*X(drand48)() - 1.0; /* for debugging: use k+1 */
printf(" a_%-2d = %+5.3lE\n",k,creal(a[k]));
}
}
/* fast polynomial transform */
fpt_trafo(set,0,a,b,N,0U);
/* Renormalize coefficients b_j, j=1,2,...,N-1 owing to how FFTW defines a
* DCT-I; see
* http://www.fftw.org/fftw3_doc/1d-Real_002deven-DFTs-_0028DCTs_0029.html
* for details */
{
int j;
for (j = 1; j < N; j++)
b[j] *= 0.5;
}
/* discrete cosine transform */
fftw_execute(p);
{
int j;
printf("\n3) Function values f_j, j=1,1,...,M:\n");
for (j = 0; j <= N; j++)
printf(" f_%-2d = %+5.3lE\n",j,f[j]);
}
/* cleanup */
free(a);
free(b);
free(f);
/* cleanup */
fftw_destroy_plan(p);
}
/* cleanup */
fpt_finalize(set);
free(alpha);
free(beta);
free(gamma);
return EXIT_SUCCESS;
}
