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Fix TensorPrimitives.IndexOfMaxMagnitude signed integer tie #128484

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Fix TensorPrimitives.IndexOfMaxMagnitude signed integer tie #128484

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edd77d6
Add unit tests
lilinus May 22, 2026
cac8cea
Fix IndexOfMin/MaxMagnitude
lilinus May 22, 2026
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12 changes: 9 additions & 3 deletions ...erics.Tensors/src/System/Numerics/Tensors/netcore/TensorPrimitives.IndexOfMaxMagnitude.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -72,7 +72,9 @@ public static Vector128<T> Compare(Vector128<T> x, Vector128<T> y)
|| typeof(T) == typeof(nint))
{
// Consider overflows (when IsNegative(Abs(x))) from Abs(MinValue) which implies maximum magnitude.
return Vector128.AndNot(Vector128.GreaterThan(xMag, yMag) | IsNegative(xMag), IsNegative(yMag));
Vector128<T> equalResult = Vector128.IsPositive(x) & Vector128.IsNegative(y);
Vector128<T> nonOverflowResult = Vector128.GreaterThan(xMag, yMag) | (Vector128.Equals(xMag, yMag) & equalResult);
return Vector128.AndNot(nonOverflowResult | IsNegative(xMag), IsNegative(yMag));
}
else
{
Expand All @@ -96,7 +98,9 @@ public static Vector256<T> Compare(Vector256<T> x, Vector256<T> y)
|| typeof(T) == typeof(nint))
{
// Consider overflows (when IsNegative(Abs(x))) from Abs(MinValue) which implies maximum magnitude.
return Vector256.AndNot(Vector256.GreaterThan(xMag, yMag) | IsNegative(xMag), IsNegative(yMag));
Vector256<T> equalResult = Vector256.IsPositive(x) & Vector256.IsNegative(y);
Vector256<T> nonOverflowResult = Vector256.GreaterThan(xMag, yMag) | (Vector256.Equals(xMag, yMag) & equalResult);
return Vector256.AndNot(nonOverflowResult | Vector256.IsNegative(xMag), Vector256.IsNegative(yMag));
}
else
{
Expand All @@ -120,7 +124,9 @@ public static Vector512<T> Compare(Vector512<T> x, Vector512<T> y)
|| typeof(T) == typeof(nint))
{
// Consider overflows (when IsNegative(Abs(x))) from Abs(MinValue) which implies maximum magnitude.
return Vector512.AndNot(Vector512.GreaterThan(xMag, yMag) | IsNegative(xMag), IsNegative(yMag));
Vector512<T> equalResult = Vector512.IsPositive(x) & Vector512.IsNegative(y);
Vector512<T> nonOverflowResult = Vector512.GreaterThan(xMag, yMag) | (Vector512.Equals(xMag, yMag) & equalResult);
return Vector512.AndNot(nonOverflowResult | Vector512.IsNegative(xMag), Vector512.IsNegative(yMag));
}
else
{
Expand Down
12 changes: 9 additions & 3 deletions ...erics.Tensors/src/System/Numerics/Tensors/netcore/TensorPrimitives.IndexOfMinMagnitude.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -72,7 +72,9 @@ public static Vector128<T> Compare(Vector128<T> x, Vector128<T> y)
|| typeof(T) == typeof(nint))
{
// Consider overflows (when IsNegative(Abs(x))) from Abs(MinValue) which implies maximum magnitude.
return Vector128.AndNot(Vector128.LessThan(xMag, yMag) | IsNegative(yMag), IsNegative(xMag));
Vector128<T> equalResult = Vector128.IsNegative(x) & Vector128.IsPositive(y);
Vector128<T> nonOverflowResult = Vector128.LessThan(xMag, yMag) | (Vector128.Equals(xMag, yMag) & equalResult);
return Vector128.AndNot(nonOverflowResult | Vector128.IsNegative(yMag), Vector128.IsNegative(xMag));
}
else
{
Expand All @@ -96,7 +98,9 @@ public static Vector256<T> Compare(Vector256<T> x, Vector256<T> y)
|| typeof(T) == typeof(nint))
{
// Consider overflows (when IsNegative(Abs(x))) from Abs(MinValue) which implies maximum magnitude.
return Vector256.AndNot(Vector256.LessThan(xMag, yMag) | IsNegative(yMag), IsNegative(xMag));
Vector256<T> equalResult = Vector256.IsNegative(x) & Vector256.IsPositive(y);
Vector256<T> nonOverflowResult = Vector256.LessThan(xMag, yMag) | (Vector256.Equals(xMag, yMag) & equalResult);
return Vector256.AndNot(nonOverflowResult | Vector256.IsNegative(yMag), Vector256.IsNegative(xMag));
}
else
{
Expand All @@ -120,7 +124,9 @@ public static Vector512<T> Compare(Vector512<T> x, Vector512<T> y)
|| typeof(T) == typeof(nint))
{
// Consider overflows (when IsNegative(Abs(x))) from Abs(MinValue) which implies maximum magnitude.
return Vector512.AndNot(Vector512.LessThan(xMag, yMag) | IsNegative(yMag), IsNegative(xMag));
Vector512<T> equalResult = Vector512.IsNegative(x) & Vector512.IsPositive(y);
Vector512<T> nonOverflowResult = Vector512.LessThan(xMag, yMag) | (Vector512.Equals(xMag, yMag) & equalResult);
return Vector512.AndNot(nonOverflowResult | Vector512.IsNegative(yMag), Vector512.IsNegative(xMag));
}
else
{
Expand Down
3 changes: 2 additions & 1 deletion src/libraries/System.Numerics.Tensors/tests/TensorPrimitives.Generic.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2725,7 +2725,8 @@ public unsafe abstract class GenericNumberTensorPrimitivesTests<T> : TensorPrimi
protected override T SumOfSquares(ReadOnlySpan<T> x) => TensorPrimitives.SumOfSquares(x);

protected override T ConvertFromSingle(float f) => T.CreateTruncating(f);
protected override bool IsFloatingPoint => typeof(T) == typeof(Half) || base.IsFloatingPoint;
protected override bool IsFloatingPoint => typeof(T) == typeof(NFloat) || typeof(T) == typeof(Half) || base.IsFloatingPoint;
protected override bool IsUnsignedInteger => typeof(T) == typeof(UInt128) || typeof(T) == typeof(nuint) || base.IsUnsignedInteger;

protected override T NextRandom()
{
Expand Down
113 changes: 95 additions & 18 deletions src/libraries/System.Numerics.Tensors/tests/TensorPrimitivesTests.cs
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Expand Up @@ -105,6 +105,9 @@ public abstract class TensorPrimitivesTests<T> where T : unmanaged, IEquatable<T
public delegate bool SpanIsAllAnyDelegate(ReadOnlySpan<T> x);

protected virtual bool IsFloatingPoint => typeof(T) == typeof(float) || typeof(T) == typeof(double);
protected virtual bool IsUnsignedInteger =>
typeof(T) == typeof(byte) || typeof(T) == typeof(ushort) || typeof(T) == typeof(uint) ||
typeof(T) == typeof(ulong) || typeof(T) == typeof(char);

protected virtual int? IndexOfSizeExceedingMaxValue() =>
(typeof(T) == typeof(byte) || typeof(T) == typeof(sbyte)) ? Helpers.SizeGreaterThanByte :
Expand Down Expand Up @@ -1138,6 +1141,18 @@ public void IndexOfMax_Negative0LesserThanPositive0()
Assert.Equal(0, IndexOfMax([ConvertFromSingle(+0f), ConvertFromSingle(-0f)]));
Assert.Equal(1, IndexOfMax([ConvertFromSingle(-1), ConvertFromSingle(-0f)]));
Assert.Equal(2, IndexOfMax([ConvertFromSingle(-1), ConvertFromSingle(-0f), ConvertFromSingle(1f)]));

Assert.All(Helpers.TensorLengths, tensorLength =>
{
foreach (int expected in new[] { 0, tensorLength / 2, tensorLength - 1 })
{
using BoundedMemory<T> x = CreateTensor(tensorLength);
x.Span.Fill(NegativeZero);
x[expected] = Zero;
x[tensorLength - 1] = Zero;
Assert.Equal(expected, IndexOfMax(x.Span));
}
});
}

[Fact]
Expand Down Expand Up @@ -1167,17 +1182,12 @@ public void IndexOfMaxMagnitude_AllLengths()
{
foreach (int expected in new[] { 0, tensorLength / 2, tensorLength - 1 })
{
using BoundedMemory<T> x = CreateTensor(tensorLength);
FillTensor(x, MinValue);
using BoundedMemory<T> x = CreateAndFillTensor(tensorLength);

T max = x[0];
for (int i = 0; i < x.Length; i++)
{
int compared = Comparer<T>.Default.Compare(Abs(x[i]), Abs(max));
if (compared > 0 || (compared == 0 && EqualityComparer<T>.Default.Equals(x[i], max)))
{
max = x[i];
}
max = MaxMagnitude(max, x[i]);
}
x[expected] = max;

Expand All @@ -1188,11 +1198,11 @@ public void IndexOfMaxMagnitude_AllLengths()
Assert.True(actual < expected || Comparer<T>.Default.Compare(x[actual], x[expected]) > 0, $"{tensorLength} {actual} {expected} {string.Join(",", MemoryMarshal.ToEnumerable<T>(x.Memory))}");
if (IsFloatingPoint)
{
AssertEqualTolerance(Abs(x[expected]), Abs(x[actual]));
AssertEqualTolerance(x[expected], x[actual], Zero);
}
else
{
Assert.Equal(Abs(x[expected]), Abs(x[actual]));
Assert.Equal(x[expected], x[actual]);
}
}
}
Expand All @@ -1216,6 +1226,24 @@ public void IndexOfMaxMagnitude_FirstNaNReturned()
});
}

[Fact]
public void IndexOfMaxMagnitude_Negative1LesserThanPositive1()
{
if (IsUnsignedInteger) return;

Assert.All(Helpers.TensorLengths, tensorLength =>
{
foreach (int expected in new[] { 0, tensorLength / 2, tensorLength - 1 })
{
using BoundedMemory<T> x = CreateTensor(tensorLength);
x.Span.Fill(NegativeOne);
x[expected] = One;
x[tensorLength - 1] = One;
Assert.Equal(expected, IndexOfMaxMagnitude(x.Span));
}
});
}

[Fact]
public void IndexOfMaxMagnitude_Negative0LesserThanPositive0()
{
Expand All @@ -1227,6 +1255,18 @@ public void IndexOfMaxMagnitude_Negative0LesserThanPositive0()
Assert.Equal(0, IndexOfMaxMagnitude([ConvertFromSingle(+0f), ConvertFromSingle(-0f)]));
Assert.Equal(0, IndexOfMaxMagnitude([ConvertFromSingle(-1), ConvertFromSingle(-0f)]));
Assert.Equal(2, IndexOfMaxMagnitude([ConvertFromSingle(-1), ConvertFromSingle(-0f), ConvertFromSingle(1f)]));

Assert.All(Helpers.TensorLengths, tensorLength =>
{
foreach (int expected in new[] { 0, tensorLength / 2, tensorLength - 1 })
{
using BoundedMemory<T> x = CreateTensor(tensorLength);
x.Span.Fill(NegativeZero);
x[expected] = Zero;
x[tensorLength - 1] = Zero;
Assert.Equal(expected, IndexOfMaxMagnitude(x.Span));
}
});
}

[Fact]
Expand Down Expand Up @@ -1291,6 +1331,18 @@ public void IndexOfMin_Negative0LesserThanPositive0()
Assert.Equal(1, IndexOfMin([ConvertFromSingle(+0f), ConvertFromSingle(-0f), ConvertFromSingle(-0f), ConvertFromSingle(-0f), ConvertFromSingle(-0f)]));
Assert.Equal(0, IndexOfMin([ConvertFromSingle(-1), ConvertFromSingle(-0f)]));
Assert.Equal(0, IndexOfMin([ConvertFromSingle(-1), ConvertFromSingle(-0f), ConvertFromSingle(1f)]));

Assert.All(Helpers.TensorLengths, tensorLength =>
{
foreach (int expected in new[] { 0, tensorLength / 2, tensorLength - 1 })
{
using BoundedMemory<T> x = CreateTensor(tensorLength);
x.Span.Fill(Zero);
x[expected] = NegativeZero;
x[tensorLength - 1] = NegativeZero;
Assert.Equal(expected, IndexOfMin(x.Span));
}
});
}

[Fact]
Expand Down Expand Up @@ -1320,17 +1372,12 @@ public void IndexOfMinMagnitude_AllLengths()
{
foreach (int expected in new[] { 0, tensorLength / 2, tensorLength - 1 })
{
using BoundedMemory<T> x = CreateTensor(tensorLength);
FillTensor(x, MinValue);
using BoundedMemory<T> x = CreateAndFillTensor(tensorLength);

T min = x[0];
for (int i = 0; i < x.Length; i++)
{
int compared = Comparer<T>.Default.Compare(Abs(x[i]), Abs(min));
if (compared < 0 || (compared == 0 && Comparer<T>.Default.Compare(x[i], min) < 0))
{
min = x[i];
}
min = MinMagnitude(min, x[i]);
}

x[expected] = min;
Expand All @@ -1341,11 +1388,11 @@ public void IndexOfMinMagnitude_AllLengths()
Assert.True(actual < expected || Comparer<T>.Default.Compare(x[actual], x[expected]) < 0, $"{tensorLength} {actual} {expected} {string.Join(",", MemoryMarshal.ToEnumerable<T>(x.Memory))}");
if (IsFloatingPoint)
{
AssertEqualTolerance(Abs(x[expected]), Abs(x[actual]));
AssertEqualTolerance(x[expected], x[actual], Zero);
}
else
{
Assert.Equal(Abs(x[expected]), Abs(x[actual]));
Assert.Equal(x[expected], x[actual]);
}
}
}
Expand All @@ -1369,6 +1416,24 @@ public void IndexOfMinMagnitude_FirstNaNReturned()
});
}

[Fact]
public void IndexOfMinMagnitude_Negative1LesserThanPositive1()
{
if (IsUnsignedInteger) return;

Assert.All(Helpers.TensorLengths, tensorLength =>
{
foreach (int expected in new[] { 0, tensorLength / 2, tensorLength - 1 })
{
using BoundedMemory<T> x = CreateTensor(tensorLength);
x.Span.Fill(One);
x[expected] = NegativeOne;
x[tensorLength - 1] = NegativeOne;
Assert.Equal(expected, IndexOfMinMagnitude(x.Span));
}
});
}

[Fact]
public void IndexOfMinMagnitude_Negative0LesserThanPositive0()
{
Expand All @@ -1380,6 +1445,18 @@ public void IndexOfMinMagnitude_Negative0LesserThanPositive0()
Assert.Equal(1, IndexOfMinMagnitude([ConvertFromSingle(+0f), ConvertFromSingle(-0f), ConvertFromSingle(-0f), ConvertFromSingle(-0f)]));
Assert.Equal(1, IndexOfMinMagnitude([ConvertFromSingle(-1), ConvertFromSingle(-0f)]));
Assert.Equal(1, IndexOfMinMagnitude([ConvertFromSingle(-1), ConvertFromSingle(-0f), ConvertFromSingle(1f)]));

Assert.All(Helpers.TensorLengths, tensorLength =>
{
foreach (int expected in new[] { 0, tensorLength / 2, tensorLength - 1 })
{
using BoundedMemory<T> x = CreateTensor(tensorLength);
x.Span.Fill(Zero);
x[expected] = NegativeZero;
x[tensorLength - 1] = NegativeZero;
Assert.Equal(expected, IndexOfMinMagnitude(x.Span));
}
});
}

[Fact]
Expand Down
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