Optimize GPN nextLevel heuristic

lib/common.coffee

@@ -209,15 +209,6 @@ addPathMeta = (path) ->
   return path
 
 
-hammingWeight = (flags) ->
-  flags -= ((flags >> 1) & 0x55555555)
-  flags = (((flags >> 2) & 0x33333333) + (flags & 0x33333333))
-  flags = (((flags >> 4) + flags) & 0x0f0f0f0f)
-  flags += (flags >> 8)
-  flags += (flags >> 16)
-  return flags & 0x0000003f
-
-
 # Source: http://stackoverflow.com/a/6969486
 escapeRegExp = (str) ->
   return str.replace(/[\-\[\]\/\{\}\(\)\*\+\?\.\\\^\$\|]/g, "\\$&")
@@ -235,5 +226,4 @@ exports.typeOf = typeOf
 exports.pathOverlap = pathOverlap
 exports.parsePath = parsePath
 exports.addPathMeta = addPathMeta
-exports.hammingWeight = hammingWeight
 exports.escapeRegExp = escapeRegExp

lib/gpn-heuristic.js

@@ -0,0 +1,82 @@
+/**
+ * Copyright 2013-2017  Zaid Abdulla
+ *
+ * This file is part of GenieACS.
+ *
+ * GenieACS is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * GenieACS is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with GenieACS.  If not, see <http://www.gnu.org/licenses/>.
+ */
+"use strict";
+
+const WILDCARD_MULTIPLIER = 2;
+const UNDISCOVERED_DEPTH = 7;
+
+// Simple heuristic to estimate GPN count given a set of patterns to be
+// discovered. Used to decide whether to use nextLevel = false in GPN.
+// gpnPatterns is [pattern, flags]
+// pattern is a path (array)
+// flags is an int where its bits mark the segments in the pattern that
+// need refreshing. Leading 0s indicate that the pattern up to that
+// point has been discovered.
+function estimateGpnCount(gpnPatterns, depth = 0) {
+  const children = {};
+  const wildcardChildren = [];
+  let wildcardDiscovered = false;
+  let gpnCount = 0;
+
+  for (let pattern of gpnPatterns) {
+    const path = pattern[0];
+    const flags = pattern[1] >> depth;
+
+    let k = path[depth];
+
+    if (!k) {
+      if (flags & 1)
+        gpnCount = 1;
+      continue;
+    }
+
+    if (flags & 1) {
+      gpnCount = 1;
+
+      if (depth > UNDISCOVERED_DEPTH)
+        continue;
+    }
+    else if (k === "*")
+      wildcardDiscovered = true;
+
+    if (k === "*") {
+      wildcardChildren.push(pattern);
+    }
+    else {
+      children[k] = children[k] || [];
+      children[k].push(pattern);
+    }
+  }
+
+  let wildcardGpnCount = 0;
+  if (!wildcardDiscovered && wildcardChildren.length)
+      wildcardGpnCount += estimateGpnCount(wildcardChildren, depth + 1) * WILDCARD_MULTIPLIER;
+
+  for (let k of Object.keys(children)) {
+    let c = estimateGpnCount(children[k].concat(wildcardChildren), depth + 1);
+    wildcardGpnCount -= c;
+    gpnCount += c;
+  }
+
+  gpnCount += Math.max(0, wildcardGpnCount);
+
+  return gpnCount;
+}
+
+exports.estimateGpnCount = estimateGpnCount;

lib/session.coffee

@@ -27,6 +27,7 @@ PathSet = require './path-set'
 VersionedMap = require './versioned-map'
 InstanceSet = require './instance-set'
 defaultProvisions = require './default-provisions'
+gpnHeuristic = require './gpn-heuristic'
 
 MAX_ITERATIONS = 64
 
@@ -856,46 +857,6 @@ rpcRequest = (sessionContext, _declarations, callback) ->
   )
 
 
-# Simple algorithm to estimate GPN count in a set of patterns used
-# to decide whether to use nextLevel = false in GPN.
-estimateGpnCount = (patterns) ->
-  res = []
-  counts = new Map()
-  for pattern in patterns
-    c = []
-    i = -1
-    while pattern[1] >> (++ i)
-      if pattern[1] & (1 << i)
-        f = (pattern[0].wildcard & pattern[1]) | ((pattern[1] >> pattern[0].length) << pattern[0].length)
-        r = [i, f & ((1 << i) - 1), 1, new Set()]
-        res.push(c[i] = r)
-    counts.set(pattern, c)
-
-  for pattern in patterns
-    pats = patterns.filter((pat) -> return pat != pattern)
-    i = -1
-    while pattern[1] >> (++ i)
-      pats = pats.filter((pat) ->
-        return false if not pat[1] << i
-        if not pat[0][i]? or pat[0][i] == '*' or pat[0][i] == pattern[0][i]
-          if pattern[1] & pat[1] & (1 << i)
-            counts.get(pattern)[i][3].add(counts.get(pat)[i])
-          return true
-        return false
-      )
-
-  count = 0
-  for r in res
-    div = 1
-    r[3].forEach((rr) -> ++ div if rr[3].has(r))
-    if r[3].size == div - 1
-      h = common.hammingWeight(r[1])
-      if h < 8
-        count += (r[2] * Math.pow(3, h)) / div
-
-  return Math.round(count)
-
-
 generateGetRpcRequest = (sessionContext) ->
   if not (syncState = sessionContext.syncState)?
     return
@@ -952,13 +913,13 @@ generateGetRpcRequest = (sessionContext) ->
       path = paths.pop()
 
     if path
-      patterns = []
-      for p in sessionContext.deviceData.paths.find(path, true, false, 99)
-        if v = syncState.gpnPatterns.get(p)
-          patterns.push([p, (v >> path.length) << path.length])
-
       if path.length >= GPN_NEXT_LEVEL
-        est = estimateGpnCount(patterns)
+        patterns = [[path, 0]]
+        for p in sessionContext.deviceData.paths.find(path, true, false, 99)
+          if v = syncState.gpnPatterns.get(p)
+            patterns.push([p, (v >> path.length) << path.length])
+
+        est = gpnHeuristic.estimateGpnCount(patterns)
       else
         est = 0