improve hard disk access locality, another 8% (#591)
* improve hard disk access locality, another 8% * add some comments & credit * fixed format
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Van Phu DO
GitHub
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c228633b57
@ -28,18 +28,21 @@ import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.List;
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import java.util.TreeMap;
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import java.util.concurrent.atomic.AtomicInteger;
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import java.util.stream.IntStream;
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import sun.misc.Unsafe;
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public class CalculateAverage_abeobk {
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private static final boolean SHOW_ANALYSIS = false;
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private static final int CPU_CNT = Runtime.getRuntime().availableProcessors();
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private static final String FILE = "./measurements.txt";
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private static final int BUCKET_SIZE = 1 << 16;
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private static final int BUCKET_MASK = BUCKET_SIZE - 1;
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private static final int MAX_STR_LEN = 100;
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private static final int MAX_STATIONS = 10000;
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private static final long CHUNK_SZ = 1 << 22; // 4MB chunk
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private static final Unsafe UNSAFE = initUnsafe();
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private static final long[] HASH_MASKS = new long[]{
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0x0L,
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@ -52,6 +55,11 @@ public class CalculateAverage_abeobk {
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0xffffffffffffffL,
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0xffffffffffffffffL, };
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private static AtomicInteger chunk_id = new AtomicInteger(0);
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private static int chunk_cnt;
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private static long start_addr, end_addr;
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private static Stat[][] all_res;
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private static final void debug(String s, Object... args) {
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System.out.println(String.format(s, args));
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}
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@ -153,20 +161,6 @@ public class CalculateAverage_abeobk {
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}
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}
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// split into chunks
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static long[] slice(long start_addr, long end_addr, long chunk_size, int cpu_cnt) {
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long[] ptrs = new long[cpu_cnt + 1];
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ptrs[0] = start_addr;
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for (int i = 1; i < cpu_cnt; i++) {
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long addr = start_addr + i * chunk_size;
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while (addr < end_addr && UNSAFE.getByte(addr++) != '\n')
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;
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ptrs[i] = Math.min(addr, end_addr);
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}
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ptrs[cpu_cnt] = end_addr;
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return ptrs;
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}
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// idea from royvanrijn
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static final long getSemiPosCode(final long word) {
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long xor_semi = word ^ 0x3b3b3b3b3b3b3b3bL; // xor with ;;;;;;;;
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@ -189,15 +183,38 @@ public class CalculateAverage_abeobk {
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return (short) ((abs_val ^ signed) - signed);
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}
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// Thread pool worker
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static final class Worker extends Thread {
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final int thread_id;
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Worker(int i) {
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thread_id = i;
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this.start();
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}
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@Override
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public void run() {
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var map = new Node[BUCKET_SIZE + MAX_STATIONS]; // extra space for collisions
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int cnt = 0;
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int id;
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int cls = 0;
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// process in small chunk to maintain disk locality (artsiomkorzun trick)
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// but keep going instead of merging
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while ((id = chunk_id.getAndIncrement()) < chunk_cnt) {
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long addr = start_addr + id * CHUNK_SZ;
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long end = Math.min(addr + CHUNK_SZ, end_addr);
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// adjust start
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if (id > 0) {
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while (UNSAFE.getByte(addr++) != '\n')
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;
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}
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// parse loop
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// optimize for contest
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// save as much slow memory access as possible
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// about 50% key < 8chars, 25% key bettween 8-10 chars
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// keylength histogram (%) = [0, 0, 0, 0, 4, 10, 21, 15, 13, 11, 6, 6, 4, 2...
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static final Node[] parse(int thread_id, long start, long end) {
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int cls = 0;
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long addr = start;
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var map = new Node[BUCKET_SIZE + MAX_STATIONS]; // extra space for collisions
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// parse loop
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while (addr < end) {
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long row_addr = addr;
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@ -220,6 +237,7 @@ public class CalculateAverage_abeobk {
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var node = map[bucket];
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if (node == null) {
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map[bucket] = new Node(row_addr, tail, val);
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cnt++;
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break;
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}
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if (node.tail == tail) {
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@ -252,6 +270,7 @@ public class CalculateAverage_abeobk {
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var node = map[bucket];
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if (node == null) {
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map[bucket] = new Node(row_addr, word0, tail, val);
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cnt++;
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break;
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}
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if (node.word0 == word0 && node.tail == tail) {
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@ -266,7 +285,6 @@ public class CalculateAverage_abeobk {
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}
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// why not going for more? tested, slower
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long hash = word0;
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while (semipos_code == 0) {
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hash ^= word;
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@ -290,6 +308,7 @@ public class CalculateAverage_abeobk {
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var node = map[bucket];
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if (node == null) {
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map[bucket] = new Node(row_addr, word0, tail, val);
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cnt++;
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break;
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}
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if (node.contentEquals(row_addr, word0, tail, keylen)) {
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@ -301,11 +320,21 @@ public class CalculateAverage_abeobk {
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cls++;
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}
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}
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}
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if (SHOW_ANALYSIS) {
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debug("Thread %d collision = %d", thread_id, cls);
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}
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return map;
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Stat[] stats = new Stat[cnt];
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int i = 0;
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for (var node : map) {
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if (node != null) {
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stats[i++] = new Stat(node);
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}
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}
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all_res[thread_id] = stats;
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}
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}
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// thomaswue trick
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@ -329,44 +358,32 @@ public class CalculateAverage_abeobk {
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return;
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}
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try (var file = FileChannel.open(Path.of(FILE), StandardOpenOption.READ)) {
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long start_addr = file.map(MapMode.READ_ONLY, 0, file.size(), Arena.global()).address();
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var file = FileChannel.open(Path.of(FILE), StandardOpenOption.READ);
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long file_size = file.size();
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long end_addr = start_addr + file_size;
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start_addr = file.map(MapMode.READ_ONLY, 0, file.size(), Arena.global()).address();
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end_addr = start_addr + file_size;
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// only use all cpus on large file
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int cpu_cnt = file_size < 1e6 ? 1 : Runtime.getRuntime().availableProcessors();
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long chunk_size = Math.ceilDiv(file_size, cpu_cnt);
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int cpu_cnt = file_size < 1e6 ? 1 : CPU_CNT;
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chunk_cnt = (int) Math.ceilDiv(file_size, CHUNK_SZ);
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all_res = new Stat[cpu_cnt][];
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// processing
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var ptrs = slice(start_addr, end_addr, chunk_size, cpu_cnt);
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List<List<Stat>> maps = IntStream.range(0, cpu_cnt)
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.mapToObj(thread_id -> parse(thread_id, ptrs[thread_id], ptrs[thread_id + 1]))
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.map(map -> {
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List<Stat> stats = new ArrayList<>();
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for (var node : map) {
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if (node == null)
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continue;
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stats.add(new Stat(node));
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}
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return stats;
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})
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.parallel()
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.toList();
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List<Worker> workers = IntStream.range(0, cpu_cnt).mapToObj(i -> new Worker(i)).toList();
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for (var w : workers)
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w.join();
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// collect all results
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TreeMap<String, Stat> ms = new TreeMap<>();
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for (var stats : maps) {
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for (var s : stats) {
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for (var res : all_res) {
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for (var s : res) {
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var stat = ms.putIfAbsent(s.key, s);
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if (stat != null)
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stat.node.merge(s.node);
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}
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}
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// print result
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// print output
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System.out.println(ms);
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System.out.close();
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}
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}
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}
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