Module caminos_lib::policies

A policy defined to what output queue/port to request among the ones returned as possible by the routing function. Policies are designed to be applied in sequence so that there remains at most a single candidate.

One should include always the policy EnforceFlowControl or equivalent at some point. To ensure at most one candidate you may use the Random policy.

see new_virtual_channel_policy for documentation on the configuration syntax of predefined policies.

Structs

ArgumentVC

Only allows those candidates whose vc is in the allowed list.

Either

Apply a different policy to each hop.

EnforceFlowControl

Hops

Select virtual channel=packet.hops.

Identity

Does not do anything. Just a placeholder for some operations.

LabelSaturate

New label = min{old_label,value} or max{old_label,value} (value,bottom)

LabelTransform

New label = old_label*multplier+summand. (multiplier,summand,saturate_bottom,saturate_top,minimum,maximum)

LowestLabel

Select the egresses with lowest label.

LowestSinghWeight

Select the lowest value of the product of the queue length (that is, consumed credits) times the estimated hop count (usually 1 plus the distance from next router to target router) This was initially proposed for the UGAL routing. parameters=(extra_congestion,extra_distance,aggregate_buffers), which are added in the formula to allow tuning. Firth two default to 0. aggregate_buffers indicates to use all buffers instead of just the selected one.

MapEntryVC

Apply a different policy to candidates from each entry virtual channel.

MapHop

Apply a different policy to each hop.

MapLabel

Apply a different policy to candidates with each label.

NegateLabel

New label = -old_label Just until I fix the grammar to accept preceding minuses.

OccupancyFunction

Transform (l,q) into new label al+bq+clq+d where l is the label and q is the occupancy.

Random

Request a port+virtual channel at random from all available.

RequestInfo

Extra information to be used by the policies of virtual channels.

ShiftEntryVC

Only allows those candidates whose vc equals their entry vc plus some s in shifts.

Shortest

Request the port+virtual channel with more credits. Does not solve ties, so it needs to be followed by Random or something.

VCPolicyBuilderArgument

VecLabel

Vector of labels new_label = vector[old_label]

WideHops

Select virtual channel in (widthpacket.hops..width(packet.hops+1)).

Traits

VirtualChannelPolicy

How virtual channels are selected for a packet They provide the function filter(Vec) -> Vec It needs: rng, self.virtual_ports(credits and length), phit.packet.routing_info.borrow().hops, server_ports, topology.{distance,neighbour}, port_average_neighbour_queue_length, port_last_transmission We could also provide functions to declare which aspects must be computed. Thus allowing to both share when necessary and to not computing ti when unnecessary.

Functions

new_virtual_channel_policy

Build a new virtual channel policy. These policies are successive refinements over the available ones as returned by the routing function, to determine to which exit a request is done.