Tensor.CreateFromShape and Tensor.CreateFromShapeUninitialized do not work correctly when FlattenedLength == 1

[jp2masa]

Description

It is currently not possible to create a tensor with a single value (FlattenedLength == 1), because it results in an empty backing array. Explicitly specifying the strides causes an exception (The provided lengths and strides would allow you to access elements outside the provided memory.), but it should not, as no memory was provided and it should be allocated correctly by the method itself.

Reproduction Steps

To reproduce, compile and run the code for each scenario. Using CreateFromShape instead of CreateFromShapeUninitialized yields the same results.

A (without explicit strides)

var src = Tensor.Create([1.0]);
Console.WriteLine($"src lengths: {String.Join(", ", src.Lengths.ToArray())}; strides: {String.Join(", ", src.Strides.ToArray())}; flattened length: {src.FlattenedLength}");

var dst = Tensor.CreateFromShapeUninitialized<double>(src.Lengths);
Console.WriteLine($"dst lengths: {String.Join(", ", dst.Lengths.ToArray())}; strides: {String.Join(", ", dst.Strides.ToArray())}; flattened length: {src.FlattenedLength}");

src.CopyTo(dst);

B (with explicit strides)

var src = Tensor.Create([1.0]);
Console.WriteLine($"src lengths: {String.Join(", ", src.Lengths.ToArray())}; strides: {String.Join(", ", src.Strides.ToArray())}; flattened length: {src.FlattenedLength}");

var dst = Tensor.CreateFromShapeUninitialized<double>(src.Lengths, src.Strides); // <- notice the difference here
Console.WriteLine($"dst lengths: {String.Join(", ", dst.Lengths.ToArray())}; strides: {String.Join(", ", dst.Strides.ToArray())}; flattened length: {src.FlattenedLength}");

src.CopyTo(dst);

Expected behavior

In both scenarios, the values in src are successfully copied to dst.

Actual behavior

In both scenarios, an ArgumentException is thrown, but for different reasons.

A

Output

src lengths: 1; strides: 1; flattened length: 1
dst lengths: 1; strides: 0; flattened length: 1

Exception

System.ArgumentException: 'Destination is too short. (Parameter 'destination')'

B

Output

src lengths: 1; strides: 1; flattened length: 1

Exception

System.ArgumentException: 'The provided lengths and strides would allow you to access elements outside the provided memory.'

Regression?

No response

Known Workarounds

No response

Configuration

• .NET: 10.0.3
• .NET SDK: 10.0.200-preview.0.26103.119
• OS: Windows 11 Home 25H2 26200.7922
• Architecture: x64

Other information

No response

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[tannergooding]

Looks like this is rather a bug in Tensor.Create(T[]) where it fails to do stride = (length > 1) ? length : 0 and only does stride = length

Fix is simple, will have it up momentarily.