libvirt-0001/0002 + xen-0001: cpu_x86 g_strv_contains O(F×A) + x86FeatureFind O(C×F) + credit2 balance_load O(V²); 21+11 PASS; count 608→611

2026-03-27 23:02:58 -04:00 · 2026-03-27 23:02:58 -04:00 · 47a312b0c7
commit 47a312b0c7
parent 87099aaaac
26 changed files with 1308 additions and 4 deletions
--- a/defects/libvirt/unit/Libvirt0001CpuUpdateLiveAlgorithm.java
+++ b/defects/libvirt/unit/Libvirt0001CpuUpdateLiveAlgorithm.java
@ -0,0 +1,133 @@
+package defects.libvirt.unit;
+
+import java.util.*;
+
+/**
+ * libvirt-0001: virCPUx86UpdateLive() addedFeatures g_strv_contains O(F×A).
+ *
+ * Models the loop in virCPUx86UpdateLive() (cpu_x86.c:3189–3222):
+ *   for each feature in map->features:
+ *     if g_strv_contains(model->addedFeatures, feature->name) → O(A)
+ *
+ * Defective: addedFeatures is a String[] scanned linearly per feature.
+ * Fixed:     addedFeatures is a HashSet<String> with O(1) contains.
+ */
+public class Libvirt0001CpuUpdateLiveAlgorithm {
+
+    // -----------------------------------------------------------------------
+    // Defective: O(F × A) — linear strv scan per feature
+    // -----------------------------------------------------------------------
+    public static class DefectiveUpdateLive {
+        public int comparisons;
+
+        /**
+         * @param allFeatures    all F feature names in the global map
+         * @param addedFeatures  A feature names marked as "added" to this model
+         * @param modelFeatures  features explicitly in the CPU definition
+         * @return set of feature names that should be ignored
+         */
+        public Set<String> computeIgnored(List<String> allFeatures,
+                                          String[] addedFeatures,
+                                          Set<String> modelFeatures) {
+            comparisons = 0;
+            Set<String> ignored = new HashSet<>();
+
+            for (String feature : allFeatures) {
+                boolean explicit = modelFeatures.contains(feature);
+                if (!explicit && addedFeatures != null) {
+                    // g_strv_contains: O(A) linear scan
+                    for (String added : addedFeatures) {
+                        comparisons++;
+                        if (added.equals(feature)) {
+                            ignored.add(feature);
+                            break;
+                        }
+                    }
+                }
+            }
+            return ignored;
+        }
+    }
+
+    // -----------------------------------------------------------------------
+    // Fixed: O(F) — HashSet contains is O(1)
+    // -----------------------------------------------------------------------
+    public static class FixedUpdateLive {
+        public int comparisons;
+
+        public Set<String> computeIgnored(List<String> allFeatures,
+                                          Set<String> addedFeaturesSet,
+                                          Set<String> modelFeatures) {
+            comparisons = 0;
+            Set<String> ignored = new HashSet<>();
+
+            for (String feature : allFeatures) {
+                comparisons++;
+                boolean explicit = modelFeatures.contains(feature);
+                if (!explicit && addedFeaturesSet != null
+                        && addedFeaturesSet.contains(feature)) {
+                    ignored.add(feature);
+                }
+            }
+            return ignored;
+        }
+    }
+
+    // -----------------------------------------------------------------------
+    // Helpers
+    // -----------------------------------------------------------------------
+
+    public static List<String> buildFeatureMap(int count) {
+        List<String> features = new ArrayList<>();
+        for (int i = 0; i < count; i++) {
+            features.add("feat-" + i);
+        }
+        return features;
+    }
+
+    /** Build addedFeatures as String[] (defective path). */
+    public static String[] buildAddedArray(List<String> allFeatures, int addedCount) {
+        String[] added = new String[addedCount];
+        for (int i = 0; i < addedCount; i++) {
+            added[i] = allFeatures.get(i); // first addedCount features are "added"
+        }
+        return added;
+    }
+
+    /** Build addedFeatures as HashSet (fixed path). */
+    public static Set<String> buildAddedSet(List<String> allFeatures, int addedCount) {
+        Set<String> set = new HashSet<>();
+        for (int i = 0; i < addedCount; i++) {
+            set.add(allFeatures.get(i));
+        }
+        return set;
+    }
+
+    public static void main(String[] args) {
+        System.out.println("libvirt-0001: virCPUx86UpdateLive addedFeatures O(F×A) vs O(F)");
+        System.out.println("=".repeat(60));
+
+        int[] fSizes = {100, 300, 500, 800};
+        int addedCount = 50;
+
+        DefectiveUpdateLive defective = new DefectiveUpdateLive();
+        FixedUpdateLive fixed = new FixedUpdateLive();
+
+        System.out.printf("%-8s  %-8s  %-12s  %-12s  %-8s%n",
+            "F", "A", "Defect ops", "Fixed ops", "Ratio");
+
+        for (int f : fSizes) {
+            List<String> features = buildFeatureMap(f);
+            String[] addedArr = buildAddedArray(features, addedCount);
+            Set<String> addedSet = buildAddedSet(features, addedCount);
+            Set<String> modelFeatures = new HashSet<>();
+
+            defective.computeIgnored(features, addedArr, modelFeatures);
+            fixed.computeIgnored(features, addedSet, modelFeatures);
+
+            double ratio = (double) defective.comparisons / Math.max(fixed.comparisons, 1);
+            System.out.printf("%-8d  %-8d  %-12d  %-12d  %.1f×%n",
+                f, addedCount, defective.comparisons, fixed.comparisons, ratio);
+        }
+    }
+}