Sections

Sections#

A section is a consecutive group of pipeline methods that operate on the same data pattern or slicing orientation. HTTomo creates sections automatically to organise data processing and movement efficiently.

An HTTomo pipeline divided into sections

Fig. 5 Methods are grouped by data pattern. A pattern change, data saving or side-output dependency introduces a new section.#

Processing sections#

HTTomo processes one section at a time. It calculates a Blocks size that satisfies the memory requirements of every method in the section, using GPU memory estimation, then passes each block through those methods in sequence.

A new section begins when:

  • the data pattern changes between projections and sinograms;

  • a method depends on a side output produced by an earlier method;

  • a method’s output needs to be saved to disk; or

  • another method requiring padded data is encountered.

When the data pattern changes, HTTomo also re-slices the data before processing the next section.

Example#

In Fig. 5, Methods 1 and 2 operate on projections and form the first section. Method 3 requires sinograms, so HTTomo re-slices the data and starts a second section. Method 4 depends on a side output from Method 3, creating a third section that also contains Method 5.

Performance considerations#

Section boundaries may require process synchronisation, data redistribution or temporary storage. Pipelines with fewer sections are therefore generally more efficient, although some boundaries are required by the selected methods.