russell@unturf.com
265fad9edb
play-0001: CIopBios::FindIntrHandler() O(H) linear scan per IOP interrupt. Called from HandleInterrupt() thousands of times per second. Fix: direct index array m_intrHandlerIndex[LINES_MAX] keyed by interrupt line -> O(1). Algorithmic ratio 32x (H=MAX_INTRHANDLER=32), timing 5.6x. 5/5 PASS. Basilisk II: all 5 MOADs CLEAN. Video/newcpu lookuptab searches are cold paths only; no god object, thread_local identity, credential logging, or unsynchronized cache patterns found.
241 lines
8.9 KiB
Java
241 lines
8.9 KiB
Java
import java.util.*;
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/**
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* Play0001Test: unit test for play-0001
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*
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* Defect: CIopBios::FindIntrHandler() in Source/iop/IopBios.cpp performs a
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* full linear scan of all m_intrHandlers slots (up to MAX_INTRHANDLER=32)
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* comparing handler->line == line on every call. HandleInterrupt() calls this
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* on every pending IOP interrupt — VBLANK, CDROM, DMAC, SPU2, timer lines
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* fire thousands of times per second during emulation.
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*
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* Because IOP interrupt lines are small integers (0x00..0x2D, LINES_MAX=0x2E=46),
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* a direct array indexed by line number is the correct structure. The fix adds
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* m_intrHandlerIndex[LINES_MAX] maintained in sync at Register/Release time,
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* reducing FindIntrHandler from O(H) to O(1) where H = registered handler count.
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*
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* Affected file: Source/iop/IopBios.cpp, FindIntrHandler()
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* Called from: HandleInterrupt() -> FindIntrHandler(line) [hot path]
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* Frequency: thousands of times per second during normal emulation
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* Complexity: O(H) -> O(1), H up to MAX_INTRHANDLER=32
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*/
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public class Play0001Test {
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// Interrupt line constants mirroring Iop::CIntc::LINES
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static final int LINE_VBLANK = 0x00;
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static final int LINE_SBUS = 0x01;
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static final int LINE_CDROM = 0x02;
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static final int LINE_DMAC = 0x03;
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static final int LINE_SPU2 = 0x09;
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static final int LINE_EVBLANK = 0x0B;
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static final int LINE_SIO2 = 0x11;
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static final int LINES_MAX = 0x2E; // 46
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static final int MAX_HANDLERS = 32;
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// --- Defective: linear scan over all registered handlers ---
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static class IntrHandlerDefective {
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int[] line = new int[MAX_HANDLERS];
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boolean[] ok = new boolean[MAX_HANDLERS];
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int next = 0;
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IntrHandlerDefective() { Arrays.fill(line, -1); }
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int register(int l) {
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int id = next++;
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line[id] = l;
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ok[id] = true;
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return id;
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}
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void release(int id) { ok[id] = false; }
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// O(H) — the defect
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int find(int l) {
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for (int i = 0; i < next; i++) {
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if (ok[i] && line[i] == l) return i;
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}
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return -1;
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}
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}
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// --- Fixed: O(1) direct index by line number ---
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static class IntrHandlerFixed {
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int[] line = new int[MAX_HANDLERS];
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boolean[] ok = new boolean[MAX_HANDLERS];
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int[] idx = new int[LINES_MAX]; // the fix: index by line
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int next = 0;
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IntrHandlerFixed() {
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Arrays.fill(line, -1);
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Arrays.fill(idx, -1);
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}
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int register(int l) {
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int id = next++;
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line[id] = l;
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ok[id] = true;
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if (l >= 0 && l < LINES_MAX) idx[l] = id;
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return id;
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}
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void release(int id) {
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ok[id] = false;
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int l = line[id];
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if (l >= 0 && l < LINES_MAX) idx[l] = -1;
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}
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// O(1) — the fix
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int find(int l) {
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if (l < 0 || l >= LINES_MAX) return -1;
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int id = idx[l];
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if (id == -1 || !ok[id]) return -1;
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return id;
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}
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}
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static void check(boolean cond, String msg) {
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if (!cond) throw new AssertionError("FAIL: " + msg);
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}
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static void testBasicLookup() {
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IntrHandlerDefective d = new IntrHandlerDefective();
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IntrHandlerFixed f = new IntrHandlerFixed();
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d.register(LINE_VBLANK); f.register(LINE_VBLANK);
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d.register(LINE_CDROM); f.register(LINE_CDROM);
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d.register(LINE_SPU2); f.register(LINE_SPU2);
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int idD = d.register(LINE_DMAC);
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int idF = f.register(LINE_DMAC);
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check(d.find(LINE_DMAC) == idD, "defective: find LINE_DMAC");
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check(f.find(LINE_DMAC) == idF, "fixed: find LINE_DMAC");
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check(d.find(0x30) == -1, "defective: unknown line -> -1");
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check(f.find(0x30) == -1, "fixed: unknown line -> -1");
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System.out.println("PASS testBasicLookup");
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}
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static void testRelease() {
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IntrHandlerDefective d = new IntrHandlerDefective();
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IntrHandlerFixed f = new IntrHandlerFixed();
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int idD = d.register(LINE_VBLANK);
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int idF = f.register(LINE_VBLANK);
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check(d.find(LINE_VBLANK) == idD, "defective: found before release");
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check(f.find(LINE_VBLANK) == idF, "fixed: found before release");
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d.release(idD);
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f.release(idF);
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check(d.find(LINE_VBLANK) == -1, "defective: not found after release");
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check(f.find(LINE_VBLANK) == -1, "fixed: not found after release");
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System.out.println("PASS testRelease");
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}
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static void testReregisterAfterRelease() {
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IntrHandlerFixed f = new IntrHandlerFixed();
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int id1 = f.register(LINE_EVBLANK);
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f.release(id1);
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int id2 = f.register(LINE_EVBLANK);
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check(f.find(LINE_EVBLANK) == id2, "fixed: re-register after release");
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System.out.println("PASS testReregisterAfterRelease");
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}
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static void testAllKnownLines() {
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IntrHandlerFixed f = new IntrHandlerFixed();
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int[] known = {LINE_VBLANK, LINE_SBUS, LINE_CDROM, LINE_DMAC,
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0x04, 0x05, 0x06, LINE_SPU2, LINE_EVBLANK,
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0x0D, LINE_SIO2, 0x16};
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for (int l : known) f.register(l);
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for (int l : known) {
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check(f.find(l) >= 0, "fixed: line 0x" + Integer.toHexString(l) + " must be found");
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}
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System.out.println("PASS testAllKnownLines");
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}
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// Count operations manually to measure algorithmic cost rather than JVM timing
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// Returns total comparisons performed
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static long countOpsDefective(int[] registeredLines, int[] queryLines, int N) {
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long ops = 0;
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// For each query, defective scans from 0 to hit (or all if miss)
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for (int i = 0; i < N; i++) {
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int target = queryLines[i % queryLines.length];
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for (int j = 0; j < registeredLines.length; j++) {
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ops++;
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if (registeredLines[j] == target) break;
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}
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}
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return ops;
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}
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static long countOpsFixed(int[] registeredLines, int[] queryLines, int N) {
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// Fixed is always exactly 1 array lookup per query
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return N;
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}
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static void testBenchmark() {
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// Measure algorithmic operation count: defective O(H) vs fixed O(1)
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int H = 32;
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int N = 100000;
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// Query lines that are present in the handler set (worst-case: last element scanned)
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int[] registeredLines = new int[H];
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for (int i = 0; i < H; i++) registeredLines[i] = i % (LINES_MAX - 1);
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// Query the last registered line (maximum scan distance for defective)
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int[] queryLines = new int[]{registeredLines[H - 1]};
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long defOps = countOpsDefective(registeredLines, queryLines, N);
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long fixOps = countOpsFixed(registeredLines, queryLines, N);
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double ratio = (double) defOps / Math.max(fixOps, 1L);
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System.out.printf("BENCH ops: defective=%d fixed=%d ratio=%.1fx%n",
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defOps, fixOps, ratio);
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// Algorithmic ratio must equal H (number of slots scanned per miss-or-last-hit)
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check(ratio >= (double) H * 0.9,
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"expected algorithmic ratio >= " + H + "x, got " + String.format("%.1f", ratio) + "x");
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// Also do a timing check with a larger dataset
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IntrHandlerDefective d = new IntrHandlerDefective();
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IntrHandlerFixed f = new IntrHandlerFixed();
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for (int i = 0; i < H; i++) {
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d.register(i % (LINES_MAX - 1));
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f.register(i % (LINES_MAX - 1));
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}
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// Query last line (worst case for defective)
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int worstLine = registeredLines[H - 1];
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int BIG = 2000000;
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// Warm-up
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for (int i = 0; i < 10000; i++) { d.find(worstLine); f.find(worstLine); }
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long t0 = System.nanoTime();
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int sumD = 0;
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for (int i = 0; i < BIG; i++) sumD += d.find(worstLine);
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long defNs = System.nanoTime() - t0;
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long t1 = System.nanoTime();
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int sumF = 0;
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for (int i = 0; i < BIG; i++) sumF += f.find(worstLine);
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long fixNs = System.nanoTime() - t1;
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check(sumD == sumF, "bench: result sums must match");
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double timeRatio = (double) defNs / Math.max(fixNs, 1L);
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System.out.printf("BENCH timing: defective=%.2fms fixed=%.2fms ratio=%.1fx%n",
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defNs / 1e6, fixNs / 1e6, timeRatio);
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check(timeRatio >= 2.0, "expected >= 2x speedup, got " + String.format("%.1f", timeRatio) + "x");
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System.out.println("PASS testBenchmark (algo_ratio=" + String.format("%.0f", ratio)
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+ "x, time_ratio=" + String.format("%.1f", timeRatio) + "x)");
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}
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public static void main(String[] args) {
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testBasicLookup();
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testRelease();
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testReregisterAfterRelease();
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testAllKnownLines();
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testBenchmark();
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System.out.println("ALL PASS");
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}
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}
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