StreamingDistributedFFT

class ska_sdp_exec_swiftly.fourier_transform.algorithm_parameters.StreamingDistributedFFT(**fundamental_constants)

Bases: BaseParameters

Streaming Distributed Fourier Transform class

It takes the fundamental_constants dict as input (see BaseParameters class). It encompasses all building blocks of the algorithm for both subgrid -> facet and facet -> subgrid directions.

The algorithm was developed for 2D input arrays (images).

Methods Summary

add_facet_contribution(facet_contrib, ...)	Further transforms facet contributions, which then will be summed up.
add_subgrid_contribution(NjSi, ...)	Further transform subgrid contributions, which are then summed up.
extract_facet_contrib_to_subgrid(BF, ...)	Extract the facet contribution to a subgrid.
extract_subgrid_contrib_to_facet(FSi, ...)	Extract contribution of subgrid to a facet.
finish_facet(MiNjSi_sum, facet_B_mask_elem, ...)	Obtain finished facet.
finish_subgrid(summed_facets[, subgrid_masks])	Obtain finished subgrid.
prepare_facet(facet, Fb, axis, **kwargs)	Calculate the inverse FFT of a padded facet element multiplied by Fb (Fb: Fourier transform of grid correction function)
prepare_subgrid(subgrid, **kwargs)	Calculate the FFT of a padded subgrid element.

Methods Documentation

add_facet_contribution(facet_contrib, facet_off_elem, axis, **kwargs)

Further transforms facet contributions, which then will be summed up.

Parameters:

• facet_contrib – array-chunk of individual facet contributions

• facet_off_elem – facet offset for the facet_contrib array chunk

• axis – axis along which the operations are performed (0 or 1)

• kwargs – needs to contain the following if dask is used: use_dask: True nout: <number of function outputs> –> 1

Returns:

TODO??

add_subgrid_contribution(NjSi, subgrid_off_elem, facet_m0_trunc, axis, **kwargs)

Further transform subgrid contributions, which are then summed up.

Parameters:

• dims – length of tuple to be produced by create_slice (i.e. number of dimensions); int

• NjSi – TODO

• subgrid_off_elem – single subgrid offset element

• facet_m0_trunc – mask truncated to a facet (image space)

• axis – axis along which operations are performed (0 or 1)

• kwargs – needs to contain the following if dask is used: use_dask: True nout: <number of function outputs> –> 1

:return summed subgrid contributions

extract_facet_contrib_to_subgrid(BF, subgrid_off_elem, facet_m0_trunc, Fn, axis, **kwargs)

Extract the facet contribution to a subgrid.

Parameters:

• BF – TODO: ? prepared facet

• subgrid_off_elem – single subgrid offset element

• facet_m0_trunc – mask truncated to a facet (image space)

• Fn – Fourier transform of gridding function

• axis – axis along which the operations are performed (0 or 1)

• kwargs – needs to contain the following if dask is used: use_dask: True nout: <number of function outputs> –> 1

Returns:

contribution of facet to subgrid

extract_subgrid_contrib_to_facet(FSi, facet_off_elem, Fn, axis, **kwargs)

Extract contribution of subgrid to a facet.

Parameters:

• Fsi – Padded subgrid in image space

• facet_off_elem – single facet offset element

• Fn – Fourier transform of gridding function

• axis – axis along which the operations are performed (0 or 1)

• kwargs – needs to contain the following if dask is used: use_dask: True nout: <number of function outputs> –> 1

Returns:

Contribution of subgrid to facet

finish_facet(MiNjSi_sum, facet_B_mask_elem, Fb, axis, **kwargs)

Obtain finished facet.

It extracts from the padded facet (obtained from subgrid via FFT) the true-sized facet and multiplies with masked Fb. (Fb: Fourier transform of grid correction function)

Parameters:

• MiNjSi_sum – sum of subgrid contributions to a facet

• facet_B_mask_elem – a facet mask element

• Fb – Fourier transform of grid correction function

• axis – axis along which operations are performed (0 or 1)

• kwargs – needs to contain the following if dask is used: use_dask: True nout: <number of function outputs> –> 1

Returns:

finished (approximate) facet element

finish_subgrid(summed_facets, subgrid_masks=None, **kwargs)

Obtain finished subgrid. Operation performed for all axes.

Parameters:

• summed_facets – summed facets contributing to thins subgrid

• subgrid_masks – subgrid mask per axis (optional)

• kwargs – needs to contain the following if dask is used: use_dask: True nout: <number of function outputs> –> 1

Returns:

approximate subgrid element

prepare_facet(facet, Fb, axis, **kwargs)

Calculate the inverse FFT of a padded facet element multiplied by Fb (Fb: Fourier transform of grid correction function)

Parameters:

• facet – single facet element

• Fb – Fourier transform of grid correction function

• axis – axis along which operations are performed (0 or 1)

• chunk – using chunk mode or not

• kwargs – needs to contain the following if dask is used: use_dask: True nout: <number of function outputs> –> 1

Returns:

TODO: BF? prepared facet

prepare_subgrid(subgrid, **kwargs)

Calculate the FFT of a padded subgrid element. No reason to do this per-axis, so always do it for all axes.

Parameters:

• subgrid – single subgrid array element

• kwargs – needs to contain the following if dask is used: use_dask: True nout: <number of function outputs> –> 1

Returns:

Padded subgrid in image space