DynamicDependencyMetrics Class Reference

Public Member Functions
	DynamicDependencyMetrics (const CalculateNextTableProp &n, const ControlPathwaysToTable &cp, const DependencyGraph &d)
double	average_cds_chain_length (const IR::MAU::Table *tbl) const
bool	can_place_cds_in_stage (const IR::MAU::Table *tbl, ordered_set< const IR::MAU::Table * > &already_placed_in_table) const
std::pair< int, int >	get_downward_prop_score (const IR::MAU::Table *a, const IR::MAU::Table *b) const
int	placeable_cds_count (const IR::MAU::Table *tbl, ordered_set< const IR::MAU::Table * > &already_placed_in_stage) const
void	score_on_seq (const IR::MAU::TableSeq *seq, const IR::MAU::Table *tbl, int &max_dep_impact, char type) const
int	total_deps_of_dom_frontier (const IR::MAU::Table *a) const
void	update_placed_tables (std::function< bool(const IR::MAU::Table *)> pt)

Member Function Documentation

average_cds_chain_length()

double DynamicDependencyMetrics::average_cds_chain_length

(

const IR::MAU::Table *

tbl

)

const

Return the average chain length of every table in the control dominating set

can_place_cds_in_stage()

bool DynamicDependencyMetrics::can_place_cds_in_stage	(	const IR::MAU::Table *	tbl,
		ordered_set< const IR::MAU::Table * > &	already_placed_in_stage ) const

Given what has already been placed within a stage, return if the table, and any table that the next table has to be propagated into can be placed in this stage due to dependencies. Relevant for Tofino.

get_downward_prop_score()

std::pair< int, int > DynamicDependencyMetrics::get_downward_prop_score	(	const IR::MAU::Table *	a,
		const IR::MAU::Table *	b ) const

So in Tofino specifically, this is to help place tables in sequences due to the other tables. Let's look at the following example:

apply() { t1.apply(); if (t2.apply().hit) { t3.apply(); } t4.apply(); }

The sequence nodes in this case will be:

[ t1, t2, t4 ] | | $hit | V [ t3 ]

Now I'm going to assign dependency chains, though let's say that these have no direct dependencies with each other:

t1 - 7
t2 - 9
t3 - 0
t4 - 8

When we place table t2, t3 must be placed before any other tables hit. However, t3 will not be favored directly. But in this case, because t4 is waiting, the metrics for t3 must see this function.

The purpose of this function is to compare two tables, specifically the different tables that they affect until they get placed, and get the max dependency chain from all tables that this particular table is waiting on. This is called a downward propagation score as we are propagating dependency information down from a control flow dominator.

TODO: Eventually instead of the top TableSequence, all table sequences leading up to that table should be analyzedj

This constraint is completely voided in Tofino2

placeable_cds_count()

int DynamicDependencyMetrics::placeable_cds_count	(	const IR::MAU::Table *	tbl,
		ordered_set< const IR::MAU::Table * > &	already_placed_in_stage ) const

Given what has already been placed within a stage, return the number of tables that can be placed of this table next table dominating set

score_on_seq()

void DynamicDependencyMetrics::score_on_seq	(	const IR::MAU::TableSeq *	seq,
		const IR::MAU::Table *	tbl,
		int &	max_dep_impact,
		char	type ) const

Copyright (C) 2024 Intel Corporation

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

SPDX-License-Identifier: Apache-2.0

total_deps_of_dom_frontier()

int DynamicDependencyMetrics::total_deps_of_dom_frontier

(

const IR::MAU::Table *

a

)

const

Based on how many dependencies are within the control dominating set.