 	// Create simulated characteristics and data
     thrust::host_vector<double> h_true_chi(n * p);
     double sigma_msmt[5] = {2.2e-4, 3.3e-4, 5.2e-4, 3.7e-4, 2.2e-4};  // Standard deviation for the measurement errors
-    double lambda[5] = {70.0, 170.0, 250.0, 350.0, 500.0};  // frequency bands correspond to Herschel PACS and SPIRES wavelengths
-    double frequencies[5];
-    for (int k=0; k<m; k++) {
-        frequencies[k] = 1e6 / lambda[i];
-    }
     
 	for (int i=0; i<n; i++) {
         // Loop over the data indices

// Function to compute the conditional log-density of the measurements given the chi value
__device__
double logdensity_meas(double* meas, double* meas_unc, int m, double* chi) {
    
    
    
    
    double centered_meas = meas_i - new_chi;
    double logdens_meas = -0.5 * centered_meas * centered_meas / (meas_unc_i * meas_unc_i);

}

// Function to compute the conditional log-density of the chi values given theta
__device__ __host__
double logdensity_pop(double* chi, double* theta) {
    
}

// Initialize the random number generator state


// Perform the MHA update on the n characteristics, done in parallel on the GPU.
__global__
void update_chi(double* chi, double* meas, double* meas_unc, int n, double* logdens, double* prop_cholfact,
                curandState* state, int current_iter)
{
	int i = blockDim.x * blockIdx.x + threadIdx.x;
