test bigLFSR

Author: breandan

src/commonMain/kotlin/ai/hypergraph/kaliningraph/sampling/Samplers.kt

@@ -288,7 +288,7 @@ fun makeBigIntFromTaps(taps: List<Int>): BigInteger =
   }.reduce { a, c -> a.or(c) }.or(BigInteger.ONE)
 
 fun makeRandBigInt(len: Int): BigInteger =
-    BigInteger.parseString(Array(len) { if(Random.nextBoolean()) '1' else '0' }.joinToString(""), 2) + 1
+    BigInteger.parseString(Array(len) { if (it == 0) '1' else if (Random.nextBoolean()) '1' else '0' }.joinToString(""), 2) + 1
 
 class BigLFSR(primitivePoly: BigInteger, val start: BigInteger = BigInteger.ONE) {
   private val taps: BigInteger = primitivePoly.shr(1)

src/commonTest/kotlin/ai/hypergraph/kaliningraph/sampling/SamplingTest.kt

@@ -3,6 +3,7 @@ package ai.hypergraph.kaliningraph.sampling
 import ai.hypergraph.kaliningraph.choose
 import ai.hypergraph.kaliningraph.types.times
 import kotlin.math.pow
+import kotlin.random.Random
 import kotlin.test.*
 
 /*
@@ -35,6 +36,14 @@ class SamplingTest {
       assertEquals(2.0.pow(i).toInt(), distinct.size + 1)
     }
 
+/*
+./gradlew jvmTest --tests "ai.hypergraph.kaliningraph.sampling.SamplingTest.testBigLFSR"
+*/
+  @Test
+  fun testBigLFSR() =
+    listOf(11, 101, 1_001, 10_001, 100_001).map { it + 2 * it * Random.nextDouble().toInt() }
+      .forEach { i -> assertEquals(i, bigLFSRSequence(i).toList().distinct().size) }
+
 /*
 ./gradlew jvmTest --tests "ai.hypergraph.kaliningraph.sampling.SamplingTest.testMDSampler"
 */