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/*
* Copyright (c) 2015-2016, Intel Corporation
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Intel Corporation nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/** \file
* \brief Add redundancy to graph to assist in SOM analysis.
*
* Currently patterns of the form:
*
* /(GET|POST).*foo/
*
* baffle our SOM analysis as the T's get merged into one by our graph
* reductions and they lose the fixed depth property. One way to solve this is
* to tell the T vertex to go fork itself before we do the main SOM pass.
*
* Overall plan:
*
* 1. build a topo ordering
* 2. walk vertices in topo order
* 3. fix up vertices where possible
* 4. go home
*
* Vertex fix up plan:
*
* 1. consider depth of vertex
* - if vertex is at fixed depth continue to next vertex
* - if vertex can be at an unbounded depth continue to next vertex
* - if vertex has a pred which is not a fixed depth continue to next vertex
* 2. group preds by their depth
* 3. for each group:
* - create a clone of the vertex (vertex props and out edges)
* - create edges from each vertex in the group to the clone
* - work out the depth for the clone
* 4. blow away original vertex
*
* Originally in UE-1862.
*/
#include "ng_som_add_redundancy.h"
#include "ng_dump.h"
#include "ng_holder.h"
#include "ng_util.h"
#include "ue2common.h"
#include "util/container.h"
#include "util/depth.h"
#include "util/graph.h"
#include "util/graph_range.h"
using namespace std;
namespace ue2 {
/** \brief Hard limit on the maximum number of new vertices to create. */
static const size_t MAX_NEW_VERTICES = 32;
static
const DepthMinMax &getDepth(NFAVertex v, const NGHolder &g,
const vector<DepthMinMax> &depths) {
return depths.at(g[v].index);
}
static
bool hasFloatingPred(NFAVertex v, const NGHolder &g,
const vector<DepthMinMax> &depths) {
for (auto u : inv_adjacent_vertices_range(v, g)) {
const DepthMinMax &d = getDepth(u, g, depths);
if (d.min != d.max) {
return true;
}
}
return false;
}
static
bool forkVertex(NFAVertex v, NGHolder &g, vector<DepthMinMax> &depths,
set<NFAVertex> &dead, size_t *numNewVertices) {
map<depth, vector<NFAEdge>> predGroups;
for (const auto &e : in_edges_range(v, g)) {
const DepthMinMax &d = getDepth(source(e, g), g, depths);
assert(d.min == d.max);
predGroups[d.min].push_back(e);
}
DEBUG_PRINTF("forking vertex with %zu pred groups\n", predGroups.size());
if (*numNewVertices + predGroups.size() > MAX_NEW_VERTICES) {
return false;
}
*numNewVertices += predGroups.size();
for (auto &group : predGroups) {
const depth &predDepth = group.first;
const vector<NFAEdge> &preds = group.second;
// Clone v for this depth with all its associated out-edges.
u32 clone_idx = depths.size(); // next index to be used
NFAVertex clone = add_vertex(g[v], g);
depth clone_depth = predDepth + 1;
g[clone].index = clone_idx;
depths.push_back(DepthMinMax(clone_depth, clone_depth));
DEBUG_PRINTF("cloned vertex %u with depth %s\n", clone_idx,
clone_depth.str().c_str());
// Add copies of the out-edges from v.
for (const auto &e : out_edges_range(v, g)) {
add_edge(clone, target(e, g), g[e], g);
}
// Add in-edges from preds in this group.
for (const auto &e : preds) {
add_edge(source(e, g), clone, g[e], g);
}
}
clear_vertex(v, g);
dead.insert(v);
return true;
}
bool addSomRedundancy(NGHolder &g, vector<DepthMinMax> &depths) {
DEBUG_PRINTF("entry\n");
const vector<NFAVertex> ordering = getTopoOrdering(g);
set<NFAVertex> dead;
size_t numNewVertices = 0;
for (auto it = ordering.rbegin(), ite = ordering.rend(); it != ite; ++it) {
NFAVertex v = *it;
if (is_special(v, g)) {
continue;
}
if (!in_degree(v, g)) {
continue; // unreachable, probably killed
}
const DepthMinMax &d = getDepth(v, g, depths);
DEBUG_PRINTF("vertex %zu has depths %s\n", g[v].index,
d.str().c_str());
if (d.min == d.max) {
DEBUG_PRINTF("fixed depth\n");
continue;
}
if (d.max.is_unreachable()) {
DEBUG_PRINTF("unbounded depth\n");
continue;
}
if (hasFloatingPred(v, g, depths)) {
DEBUG_PRINTF("has floating pred\n");
continue;
}
if (!forkVertex(v, g, depths, dead, &numNewVertices)) {
DEBUG_PRINTF("new vertex limit reached\n");
break;
}
}
assert(numNewVertices <= MAX_NEW_VERTICES);
if (dead.empty()) {
return false; // no changes made to the graph
}
remove_vertices(dead, g);
return true;
}
} // namespace ue2
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