russell@unturf.com
db29a08762
B&W print-friendly diagrams + tinkerpop-0001 + wave-3 proof sections. Squash of 94 local commits onto remote master.
49 lines
1.4 KiB
Markdown
49 lines
1.4 KiB
Markdown
# 0004 — Dependencies$GraphDependencies$Node: List.contains() dedup on every addDependency()
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**Status:** open
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**Severity:** performance — low-medium
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**Component:** `jdk.compiler / com.sun.tools.javac.util.Dependencies$GraphDependencies$Node`
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---
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## Root Cause
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`Dependencies.java:199`:
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```java
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void addDependency(DependencyKind depKind, Node dep) {
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List<Node> deps = depsByKind.get(depKind);
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if (!deps.contains(dep)) { // O(N) linear scan before every add
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deps.add(dep);
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}
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}
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```
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`deps` is a `java.util.ArrayList<Node>`. The deduplication check scans the entire list on every `addDependency()` call. Should be a `LinkedHashSet` (O(1) add with deduplication, preserves insertion order).
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---
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## Fix
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```java
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// Replace ArrayList with LinkedHashSet in Node constructor:
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EnumMap<CompletionCause, Set<Node>> depsByKind; // Set, not List
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Node(ClassSymbol value) {
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super(value);
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this.depsByKind = new EnumMap<>(CompletionCause.class);
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for (CompletionCause depKind : CompletionCause.values()) {
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depsByKind.put(depKind, new LinkedHashSet<>()); // O(1) add + dedup
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}
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}
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void addDependency(DependencyKind depKind, Node dep) {
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depsByKind.get(depKind).add(dep); // dedup is free, no contains() needed
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}
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```
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---
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## Context
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`GraphDependencies` is only active when the `debug.completionDeps` option is set (disabled by default). Impact is limited to debug/diagnostic compilation runs. Severity lower than 0001–0003.
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