5.2. Poset Syncing

This module implements functions useful for syncing posets.

aleph.actions.poset_syncing.dehash_parents(poset, U)

Substitute units from the poset for hashes in U’s parent list and set the height field. To be called on units received from the network.

Parameters

• poset (Poset) – the poset where U is supposed to end up in

• U (Unit) – the unit with hashes instead of parents

aleph.actions.poset_syncing.order_units_topologically(units_list)

Outputs a topological order of units_list. More formally it outputs a list top_list such that: whenever U, V are in units_list and V is a parent of U then V appears before U in top_list. Note: this does not necessarily preserve the ordering in the poset!

Parameters

unit_list (list) – the list of units to sort

Returns

topologically sorted unit_list

aleph.actions.poset_syncing.poset_info(poset)

A short representation of the poset state, for syncing purposes.

Parameters

poset (Poset) – the poset which state we want to receive

Returns

A list of lists of pairs (height, hash), with the heights and hashes of maximal elements per process in the poset.

aleph.actions.poset_syncing.requested_units_to_send(poset, tops, requests)

Collect units to send given the provided request.

Parameters

• poset (Poset) – the poset which is supposed to be the source of the units

• tops (list) – the short representation of the receiving poset’s top known units made by pid

• requests (list) – the hashes of the requested units

Returns

units created by pid the other poset requested and has not yet seen

aleph.actions.poset_syncing.units_to_send(poset, info, requests=None)

Determine which units to send to a poset which has the given info.

Parameters

• poset (Poset) – the poset which is supposed to be the source of the units

• info (list) – the short representation of the receiving poset’s state

• requests (list) – a list of explicitly requested units, per process

Returns

units the other poset should receive to catch up to us

aleph.actions.poset_syncing.units_to_send_with_pid(poset, tops, pid)

Determine which units created by pid to send to a poset which has the top known units of pid as given. Also make a list of units in tops we don’t recognize.

Parameters

• poset (Poset) – the poset which is supposed to be the source of the units

• tops (list) – the short representation of the receiving poset’s top known units made by pid

• pid (int) – the id of the creator of units we are interested in

Returns

units created by pid the other poset should receive to catch up to us, and a list of tops we don’t recognize