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Fix bug in Equihash.IntListMultimap & adjust constants

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Fix a trivial bug in the iterator returned by 'IntListMultimap::get',
caused by mistaken use of the iterator index in place of the key when
doing lookups into the overspill map. This was causing puzzle solutions
to be invalid about 3% of the time, as well as substantially reducing
the average number of solutions found per nonce.

As the fix increases the mean solution count per nonce to the correct
value of 2.0 predicted by the paper (regardless of puzzle params k & n),
inline the affected constants to simplify 'Equihash::adjustDifficulty'.
This commit is contained in:
Steven Barclay 2021-11-30 21:26:17 +00:00 • committed by Christoph Atteneder
parent 92209c3ed7
commit c9c2be6dcd
No known key found for this signature in database
GPG key ID: CD5DC1C529CDFD3B
3 changed files with 34 additions and 37 deletions
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12
common/src/main/java/bisq/common/crypto/Equihash.java
View file

@ -81,10 +81,8 @@ import static java.math.BigInteger.ONE;
@SuppressWarnings("UnstableApiUsage") @SuppressWarnings("UnstableApiUsage")
public class Equihash { public class Equihash {
private static final int HASH_BIT_LENGTH = 256; private static final int HASH_BIT_LENGTH = 256;
/** Observed mean solution count per nonce for Equihash-n-4 puzzles with unit difficulty. */ /** Mean solution count per nonce for Equihash puzzles with unit difficulty. */
public static final double EQUIHASH_n_4_MEAN_SOLUTION_COUNT_PER_NONCE = 1.63; private static final double MEAN_SOLUTION_COUNT_PER_NONCE = 2.0;
/** Observed mean solution count per nonce for Equihash-n-5 puzzles with unit difficulty. */
public static final double EQUIHASH_n_5_MEAN_SOLUTION_COUNT_PER_NONCE = 1.34;
private final int k, N; private final int k, N;
private final int tableCapacity; private final int tableCapacity;
@ -127,8 +125,8 @@ public class Equihash {
/** Adjust the provided difficulty to take the variable number of puzzle solutions per /** Adjust the provided difficulty to take the variable number of puzzle solutions per
* nonce into account, so that the expected number of attempts needed to solve a given * nonce into account, so that the expected number of attempts needed to solve a given
* puzzle equals the reciprocal of the provided difficulty. */ * puzzle equals the reciprocal of the provided difficulty. */
public static double adjustDifficulty(double realDifficulty, double meanSolutionCountPerNonce) { public static double adjustDifficulty(double realDifficulty) {
return Math.max(-meanSolutionCountPerNonce / Math.log1p(-1.0 / Math.max(realDifficulty, 1.0)), 1.0); return Math.max(-MEAN_SOLUTION_COUNT_PER_NONCE / Math.log1p(-1.0 / Math.max(realDifficulty, 1.0)), 1.0);
} }
public Puzzle puzzle(byte[] seed) { public Puzzle puzzle(byte[] seed) {
@ -339,7 +337,7 @@ public class Equihash {
private Iterator<Integer> overspillIterator() { private Iterator<Integer> overspillIterator() {
if (overspillIterator == null) { if (overspillIterator == null) {
overspillIterator = overspillMultimap.get(i).iterator(); overspillIterator = overspillMultimap.get(key).iterator();
} }
return overspillIterator; return overspillIterator;
} }

3
common/src/main/java/bisq/common/crypto/EquihashProofOfWorkService.java
View file

@ -70,7 +70,6 @@ public class EquihashProofOfWorkService extends ProofOfWorkService {
} }
private static double scaledDifficulty(double difficulty) { private static double scaledDifficulty(double difficulty) {
return Equihash.adjustDifficulty(DIFFICULTY_SCALE_FACTOR * difficulty, return Equihash.adjustDifficulty(DIFFICULTY_SCALE_FACTOR * difficulty);
Equihash.EQUIHASH_n_5_MEAN_SOLUTION_COUNT_PER_NONCE);
} }
} }

56
common/src/test/java/bisq/common/crypto/EquihashTest.java
View file

@ -33,7 +33,6 @@ import java.util.stream.IntStream;
import org.junit.Ignore; import org.junit.Ignore;
import org.junit.Test; import org.junit.Test;
import static bisq.common.crypto.Equihash.EQUIHASH_n_5_MEAN_SOLUTION_COUNT_PER_NONCE;
import static java.lang.Double.POSITIVE_INFINITY; import static java.lang.Double.POSITIVE_INFINITY;
import static org.junit.Assert.assertEquals; import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue; import static org.junit.Assert.assertTrue;
@ -56,16 +55,17 @@ public class EquihashTest {
@Test @Test
public void testAdjustDifficulty() { public void testAdjustDifficulty() {
assertEquals(1.0, Equihash.adjustDifficulty(0.0, 1.34), 0.0001); assertEquals(1.0, Equihash.adjustDifficulty(0.0), 0.0001);
assertEquals(1.0, Equihash.adjustDifficulty(0.5, 1.34), 0.0001); assertEquals(1.0, Equihash.adjustDifficulty(0.5), 0.0001);
assertEquals(1.0, Equihash.adjustDifficulty(1.0, 1.34), 0.0001); assertEquals(1.0, Equihash.adjustDifficulty(1.0), 0.0001);
assertEquals(1.0, Equihash.adjustDifficulty(1.2, 1.34), 0.0001); assertEquals(1.0, Equihash.adjustDifficulty(1.1), 0.0001);
assertEquals(1.22, Equihash.adjustDifficulty(1.5, 1.34), 0.01); assertEquals(1.12, Equihash.adjustDifficulty(1.2), 0.01);
assertEquals(1.93, Equihash.adjustDifficulty(2.0, 1.34), 0.01); assertEquals(1.83, Equihash.adjustDifficulty(1.5), 0.01);
assertEquals(2.62, Equihash.adjustDifficulty(2.5, 1.34), 0.01); assertEquals(2.89, Equihash.adjustDifficulty(2.0), 0.01);
assertEquals(3.30, Equihash.adjustDifficulty(3.0, 1.34), 0.01); assertEquals(3.92, Equihash.adjustDifficulty(2.5), 0.01);
assertEquals(134.0, Equihash.adjustDifficulty(100.0, 1.34), 1.0); assertEquals(4.93, Equihash.adjustDifficulty(3.0), 0.01);
assertEquals(Equihash.adjustDifficulty(POSITIVE_INFINITY, 1.34), POSITIVE_INFINITY, 1.0); assertEquals(200.0, Equihash.adjustDifficulty(100.0), 1.5);
assertEquals(Equihash.adjustDifficulty(POSITIVE_INFINITY), POSITIVE_INFINITY, 1.0);
} }
@Test @Test
@ -87,12 +87,12 @@ public class EquihashTest {
public void benchmarkFindSolution() { public void benchmarkFindSolution() {
// On Intel Core i3 CPU M 330 @ 2.13GHz ... // On Intel Core i3 CPU M 330 @ 2.13GHz ...
// //
// For Equihash-90-5 with real difficulty 2.0, adjusted difficulty 1.933211354791211 ... // For Equihash-90-5 with real difficulty 2.0, adjusted difficulty 2.8853900817779268 ...
// Total elapsed solution time: 292789 ms // Total elapsed solution time: 279583 ms
// Mean time to solve one puzzle: 292 ms // Mean time to solve one puzzle: 279 ms
// Puzzle solution time per unit difficulty: 146 ms // Puzzle solution time per unit difficulty: 139 ms
// //
double adjustedDifficulty = Equihash.adjustDifficulty(2.0, EQUIHASH_n_5_MEAN_SOLUTION_COUNT_PER_NONCE); double adjustedDifficulty = Equihash.adjustDifficulty(2.0);
Equihash equihash = new Equihash(90, 5, adjustedDifficulty); Equihash equihash = new Equihash(90, 5, adjustedDifficulty);
Stopwatch stopwatch = Stopwatch.createStarted(); Stopwatch stopwatch = Stopwatch.createStarted();
@ -140,24 +140,24 @@ public class EquihashTest {
@Ignore @Ignore
public void solutionCountPerNonceStats() { public void solutionCountPerNonceStats() {
// For Equihash-60-4... // For Equihash-60-4...
// Got puzzle solution count mean: 1.6161 // Got puzzle solution count mean: 1.9797
// Got expected count stats: [0 x 1987, 1 x 3210, 2 x 2595, 3 x 1398, 4 x 564, 5 x 183, 6 x 49, 7 x 11, 8 x 3] // Got expected count stats: [0 x 1381, 1 x 2734, 2 x 2707, 3 x 1786, 4 x 884, 5 x 350, 6 x 115, 7 x 33, 8 x 8, 9 x 2]
// Got actual count stats: [0 x 2014, 1 x 3230, 2 x 2546, 3 x 1395, 4 x 543, 5 x 191, 6 x 50, 7 x 24, 8 x 4, 9 x 3] // Got actual count stats: [0 x 1413, 1 x 2704, 2 x 2699, 3 x 1813, 4 x 866, 5 x 330, 6 x 115, 7 x 35, 8 x 19, 9 x 5, 10]
// //
// For Equihash-70-4... // For Equihash-70-4...
// Got puzzle solution count mean: 1.6473 // Got puzzle solution count mean: 1.9988
// Got expected count stats: [0 x 1926, 1 x 3172, 2 x 2613, 3 x 1434, 4 x 591, 5 x 195, 6 x 53, 7 x 13, 8 x 2, 9] // Got expected count stats: [0 x 1355, 1 x 2708, 2 x 2707, 3 x 1803, 4 x 902, 5 x 360, 6 x 120, 7 x 34, 8 x 9, 9 x 2]
// Got actual count stats: [0 x 1958, 1 x 3172, 2 x 2584, 3 x 1413, 4 x 585, 5 x 204, 6 x 61, 7 x 17, 8 x 5, 9] // Got actual count stats: [0 x 1362, 1 x 2690, 2 x 2720, 3 x 1826, 4 x 870, 5 x 353, 6 x 129, 7 x 41, 8 x 7, 9 x 2]
// //
// For Equihash-90-5... // For Equihash-90-5...
// Got puzzle solution count mean: 1.3419 // Got puzzle solution count mean: 1.9921
// Got expected count stats: [0 x 2613, 1 x 3508, 2 x 2353, 3 x 1052, 4 x 353, 5 x 95, 6 x 21, 7 x 4, 8] // Got expected count stats: [0 x 1364, 1 x 2717, 2 x 2707, 3 x 1797, 4 x 896, 5 x 356, 6 x 119, 7 x 33, 8 x 9, 9 x 2]
// Got actual count stats: [0 x 2698, 1 x 3446, 2 x 2311, 3 x 1045, 4 x 352, 5 x 104, 6 x 33, 7 x 5, 8 x 3, 9, 10, 12] // Got actual count stats: [0 x 1379, 1 x 2709, 2 x 2729, 3 x 1750, 4 x 900, 5 x 362, 6 x 119, 7 x 39, 8 x 11, 9, 10]
// //
// For Equihash-96-5... // For Equihash-96-5...
// Got puzzle solution count mean: 1.3363 // Got puzzle solution count mean: 1.9997
// Got expected count stats: [0 x 2628, 1 x 3512, 2 x 2347, 3 x 1045, 4 x 349, 5 x 93, 6 x 21, 7 x 4, 8] // Got expected count stats: [0 x 1354, 1 x 2707, 2 x 2707, 3 x 1804, 4 x 902, 5 x 360, 6 x 121, 7 x 34, 8 x 9, 9 x 2]
// Got actual count stats: [0 x 2708, 1 x 3409, 2 x 2344, 3 x 1048, 4 x 368, 5 x 94, 6 x 23, 7 x 6] // Got actual count stats: [0 x 1405, 1 x 2621, 2 x 2733, 3 x 1802, 4 x 928, 5 x 342, 6 x 123, 7 x 29, 8 x 13, 9 x 3, 10]
// //
Equihash equihash = new Equihash(90, 5, 1.0); Equihash equihash = new Equihash(90, 5, 1.0);
byte[] seed = new byte[32]; byte[] seed = new byte[32];