Fix for Random failures in System.Numerics.Tests.modpowTest.ModPowAxi…

…om test (#74112) * Fixed #70330 * Removed pessimistic buffer cleanup
dotnet · Aug 18, 2022 · bee9904 · bee9904
1 parent 3915e94
commit bee9904
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Showing 2 changed files with 23 additions and 3 deletions.
diff --git a/src/libraries/System.Runtime.Numerics/src/System/Numerics/BigIntegerCalculator.PowMod.cs b/src/libraries/System.Runtime.Numerics/src/System/Numerics/BigIntegerCalculator.PowMod.cs
@@ -217,7 +217,11 @@ public static void Pow(ReadOnlySpan<uint> value, uint power,
  Span<uint> valueCopy = (size <= StackAllocThreshold ?
  stackalloc uint[StackAllocThreshold]
  : valueCopyFromPool = ArrayPool<uint>.Shared.Rent(size)).Slice(0, size);
- valueCopy.Clear();
+
+ // smallish optimization here:
+ // subsequent operations will copy the elements to the beginning of the buffer,
+ // no need to clear everything
+ valueCopy.Slice(value.Length).Clear();
 
  if (value.Length > modulus.Length)
  {
@@ -262,7 +266,11 @@ public static void Pow(ReadOnlySpan<uint> value, ReadOnlySpan<uint> power,
  Span<uint> valueCopy = (size <= StackAllocThreshold ?
  stackalloc uint[StackAllocThreshold]
  : valueCopyFromPool = ArrayPool<uint>.Shared.Rent(size)).Slice(0, size);
- valueCopy.Clear();
+
+ // smallish optimization here:
+ // subsequent operations will copy the elements to the beginning of the buffer,
+ // no need to clear everything
+ valueCopy.Slice(value.Length).Clear();
 
  if (value.Length > modulus.Length)
  {
@@ -464,7 +472,7 @@ private static Span<uint> PowCore(Span<uint> value, int valueLength,
  power >>= 1;
  }
 
- return result.Slice(0, resultLength);
+ return result;
  }
 
  private static Span<uint> PowCore(Span<uint> value, int valueLength,

diff --git a/src/libraries/System.Runtime.Numerics/tests/BigInteger/modpow.cs b/src/libraries/System.Runtime.Numerics/tests/BigInteger/modpow.cs
@@ -274,6 +274,18 @@ public static void ModPowAxiom()
  }
  }
 
+ [Fact]
+ public static void RegressionIssue70330()
+ {
+ byte[] tempByteArray1 = { 226, 32 };
+ byte[] tempByteArray2 = { 113 };
+ byte[] tempByteArray3 = { 15, 8, 201, 158, 96, 200, 233, 243, 184, 0, 33, 203, 210, 80, 174, 198, 244, 177, 223, 221, 168, 243, 233, 133, 103, 252, 219, 195, 187, 227, 215, 54, 66, 248, 37, 186, 232, 45, 227, 147, 100, 14, 121, 244, 56, 89, 181, 120, 205, 4, 59, 48, 65, 239, 221, 28, 30, 68, 55, 99, 237, 38, 56, 213, 40, 234, 136, 218, 42, 244, 222, 198, 205 };
+ VerifyIdentityString(
+ Print(tempByteArray3) + Print(tempByteArray2) + Print(tempByteArray1) + "tModPow",
+ Print(tempByteArray3) + Print(tempByteArray2) + Print(tempByteArray1) + "bPow" + " bRemainder"
+ );
+ }
+
  [Fact]
  public static void ModPowBoundary()
  {