The Grid class

class Grid

A 3D grid class to handle input independent functionality.

Public Types

enum index_type

The indexing type required for an Grid::index function call.

Values:

enumerator padded
enumerator real
enumerator complex_herm
enum filter_type

The type of filter to be applied to the grid to smooth it.

Values:

enumerator real_top_hat
enumerator k_top_hat
enumerator gaussian

Public Functions

Grid(const std::array<int32_t, 3> n_cell_, const std::array<double, 3> box_size_)

Basic constructor. This will allocate the grid array, and store the corresponding size in various forms.

Parameters

  • n_cell_ – The number of logical cells in each dimension

  • box_size_ – The size of the simulation volume in input units

~Grid(void)

Basic desctructor. This will free the fftw plans created during initialisation.

Grid(const Grid &other)

Copy constructor.

Grid &operator=(const Grid &other)

Assignment constructor.

void update_properties(const std::array<int32_t, 3> n_cell_)

Update the “size” of the grid for a new logical size. Note that this does not alter the size of the memory allocation, just what this allocation represents.

Parameters

n_cell_ – The new number of logical cells in each dimension

float *get()

Return the pointer to the grid data.

Returns

Float pointer to the grid data.

std::complex<float> *get_complex()

Return the pointer to the grid data, cast as a complex array.

Returns

Complex pointer to the grid data

int index(const int i, const int j, const int k, const index_type type, const std::array<int, 3> shape)

Indexing function for arbitrary grid of any 3D size.

Parameters

  • i – Index in 1st dimension

  • j – Index in second dimension

  • k – Index in third dimension

  • shape – Shape of the 3D array

Returns

The index

int index(const int i, const int j, const int k, const index_type type)

Indexing function for the current grid.

Parameters

  • i – Index in 1st dimension

  • j – Index in second dimension

  • k – Index in third dimension

Returns

The index

void real_to_padded_order(void)

Convert the grid from logical memory ordering to padded ordering.

void padded_to_real_order(void)

Convert the grid from padded memory ordering to logical ordering.

void forward_fft(void)

Do the forward FFT

void reverse_fft(void)

Do the reverse FFT

void filter(filter_type type, const double R)

Filter the grid using a given filter type and size.

Parameters

  • type – The filter type to use

  • R – the size (typically radius) of the filter

void sample(const std::array<int, 3> new_n_cell)

Subsample the grid to provide a new one with the requested dimensions.

Note that the parameters of the Grid object will be updated correspondingly.

Parameters

new_n_cell – The new logical size of the grid.