From ed6499a2c74ff1e5767352f3eaa711d2675b54ce Mon Sep 17 00:00:00 2001
From: Anthony Lloyd <anthony@lloydhq.com>
Date: Sun, 13 Oct 2024 09:24:13 +0100
Subject: [PATCH] current PCG with saved threshold

---
 Tests/PCGTests.cs | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/Tests/PCGTests.cs b/Tests/PCGTests.cs
index 3020852..38b5b74 100644
--- a/Tests/PCGTests.cs
+++ b/Tests/PCGTests.cs
@@ -210,7 +210,7 @@ public void Double_Exp_Bug()
     [Fact]
     public void PCG_Multiplier_Is_Not_Faster()
     {
-        Gen.Select(Gen.UInt, Gen.ULong, Gen.UInt[1, 10_000])
+        Gen.Select(Gen.UInt, Gen.ULong, Gen.UInt[2, 10_000])
         .Select((i, s, m) => (new PCG(i, s), new PCGTest(i, s), m, HashHelper.GetFastModMultiplier(m)))
         .Faster(
             (_, n, u, m) => n.Next(u, m),
@@ -226,7 +226,7 @@ static void Ignore<T>(T _) { }
     [Fact]
     public void PCG_New_Is_Not_Faster()
     {
-        Gen.Select(Gen.UInt, Gen.ULong, Gen.UInt[1, 10_000])
+        Gen.Select(Gen.UInt, Gen.ULong, Gen.UInt[2, 10_000])
         .Select((i, s, m) => (new PCG(i, s), new PCGTest(i, s), m))
         .Faster(
             (_, n, m) => Ignore(n.Next(m)),
@@ -240,7 +240,7 @@ public void PCG_New_Is_Not_Faster()
     [Fact]
     public void PCG_Lemire_Is_Faster()
     {
-        Gen.Select(Gen.UInt, Gen.ULong, Gen.UInt[1, 10_000])
+        Gen.Select(Gen.UInt, Gen.ULong, Gen.UInt[2, 10_000])
         .Select((i, s, m) => (new PCG(i, s), new PCGTest(i, s), m, ((ulong)-m) % m))
         .Faster(
             (_, n, m, t) => Ignore(n.NextLemire(m, t)),
@@ -251,6 +251,20 @@ public void PCG_Lemire_Is_Faster()
         );
     }
 
+    [Fact]
+    public void PCG_Current_With_Threshold_Is_Faster()
+    {
+        Gen.Select(Gen.UInt, Gen.ULong, Gen.UInt[2, 10_000])
+        .Select((i, s, m) => (new PCGTest(i, s), new PCGTest(i, s), m, ((uint)-(int)m) % m))
+        .Faster(
+            (_, n, m, t) => Ignore(n.NextLemire(m, t)),
+            (o, _, m, t) => Ignore(o.NextCurrentWithThreshold(m, t)),
+            repeat: 100,
+            raiseexception: false,
+            writeLine: output.WriteLine
+        );
+    }
+
     public sealed class PCGTest
     {
         static int threadCount;
@@ -311,6 +325,13 @@ public uint NextLemire(uint maxExclusive, ulong threshold)
             while ((uint)m < threshold);
             return (uint)(m >> 32);
         }
+        public uint NextCurrentWithThreshold(uint maxExclusive, uint threshold)
+        {
+            if (maxExclusive == 1U) return 0U;
+            var n = Next();
+            while (n < threshold) n = Next();
+            return n % maxExclusive;
+        }
         public ulong Next64(ulong maxExclusive)
         {
             if (maxExclusive <= uint.MaxValue) return Next((uint)maxExclusive);