Allow overriding metadata when creating a view.

Summary: .

Differential Revision: D86070964

Author: shoumikhin

extension/apple/ExecuTorch/Exported/ExecuTorch+Tensor.swift

@@ -130,6 +130,29 @@ public extension AnyTensor {
   /// The total number of elements in the tensor.
   var count: Int { __count }
 
+  /// Creates a new tensor that shares the underlying data storage with the
+  /// given tensor, with metadata overrides. An empty array for
+  /// a parameter signifies that it should be inherited or derived.
+  ///
+  /// - Parameters:
+  ///   - tensor: The tensor instance to create a view of.
+  ///   - shape: An override for the tensor's shape.
+  ///   - dimensionOrder: An override for the tensor's dimension order.
+  ///   - strides: An override for the tensor's strides.
+  convenience init(
+    _ tensor: AnyTensor,
+    shape: [Int] = [],
+    dimensionOrder: [Int] = [],
+    strides: [Int] = []
+  ) {
+    self.init(
+      __tensor: tensor,
+      shape: shape.map(NSNumber.init),
+      dimensionOrder: dimensionOrder.map(NSNumber.init),
+      strides: strides.map(NSNumber.init)
+    )
+  }
+
   /// Initializes a tensor without copying the provided data.
   ///
   /// - Parameters:
@@ -234,8 +257,7 @@ public extension AnyTensor {
 
   /// Attempts to convert this type-erased `AnyTensor` into a strongly-typed `Tensor<T>`.
   ///
-  /// - Returns: An `AnyTensor` if `self.dataType == T.dataType`,
-  ///            otherwise `nil` when the runtime dtype doesn’t match.
+  /// - Returns: A `Tensor<T>` if the runtime data type matches, otherwise `nil`.
   func asTensor<T: Scalar>() -> Tensor<T>? {
     guard dataType == T.dataType else { return nil }
     return Tensor<T>(self)
@@ -586,11 +608,28 @@ public final class Tensor<T: Scalar>: Equatable {
   }
 
   /// Creates a new tensor that shares the underlying data storage with the
-  /// given tensor. This new tensor is a view and does not own the data.
+  /// given tensor, with optional metadata overrides. An empty array for
+  /// a parameter signifies that it should be inherited or derived.
   ///
-  /// - Parameter tensor: The tensor to create a view of.
-  public convenience init(_ tensor: Tensor<T>) {
-    self.init(AnyTensor(tensor.anyTensor))
+  /// - Parameters:
+  ///   - tensor: The tensor to create a view of.
+  ///   - shape: An override for the tensor's shape.
+  ///   - dimensionOrder: An override for the tensor's dimension order.
+  ///   - strides: An override for the tensor's strides.
+  public convenience init(
+    _ tensor: Tensor<T>,
+    shape: [Int] = [],
+    dimensionOrder: [Int] = [],
+    strides: [Int] = []
+  ) {
+    self.init(
+      AnyTensor(
+        tensor.anyTensor,
+        shape: shape,
+        dimensionOrder: dimensionOrder,
+        strides: strides
+      )
+    )
   }
 
   /// Initializes a tensor without copying the provided data.
@@ -742,7 +781,6 @@ public final class Tensor<T: Scalar>: Equatable {
   }
 
   /// Returns a copy of the tensor, converted to the specified scalar type.
-  ///
   /// - Parameter dataType: The target scalar type.
   /// - Returns: A new tensor with the same shape and metadata but converted elements.
   public func copy<U: Scalar>(to dataType: U.Type) -> Tensor<U> {

extension/apple/ExecuTorch/Exported/ExecuTorchTensor.h

@@ -150,6 +150,35 @@ __attribute__((objc_subclassing_restricted))
     NS_DESIGNATED_INITIALIZER
     NS_SWIFT_UNAVAILABLE("");
 
+/**
+ * Creates a new tensor that shares the underlying data storage with the
+ * given tensor, with metadata overrides. An empty array for
+ * a parameter signifies that it should be inherited or derived.
+ *
+ * @param otherTensor The tensor instance to create a view of.
+ * @param shape An override for the tensor's shape.
+ * @param dimensionOrder An override for the tensor's dimension order.
+ * @param strides An override for the tensor's strides.
+ * @return A new ExecuTorchTensor instance that shares data with otherTensor.
+ */
+- (instancetype)initWithTensor:(ExecuTorchTensor *)otherTensor
+                         shape:(NSArray<NSNumber *> *)shape
+                dimensionOrder:(NSArray<NSNumber *> *)dimensionOrder
+                       strides:(NSArray<NSNumber *> *)strides
+    NS_REFINED_FOR_SWIFT;
+
+/**
+ * Creates a new tensor that shares the underlying data storage with the
+ * given tensor, with an overridden shape.
+ *
+ * @param otherTensor The tensor instance to create a view of.
+ * @param shape An override for the tensor's shape.
+ * @return A new ExecuTorchTensor instance that shares data with otherTensor.
+ */
+- (instancetype)initWithTensor:(ExecuTorchTensor *)otherTensor
+                         shape:(NSArray<NSNumber *> *)shape
+    NS_SWIFT_UNAVAILABLE("");
+
 /**
  * Creates a new tensor that shares the underlying data storage with the
  * given tensor. This new tensor is a view and does not own the data.
@@ -158,7 +187,7 @@ __attribute__((objc_subclassing_restricted))
  * @return A new ExecuTorchTensor instance that shares data with otherTensor.
  */
 - (instancetype)initWithTensor:(ExecuTorchTensor *)otherTensor
-    NS_SWIFT_NAME(init(_:));
+    NS_SWIFT_UNAVAILABLE("");
 
 /**
  * Creates a deep copy of the tensor.

extension/apple/ExecuTorch/Exported/ExecuTorchTensor.mm

@@ -126,10 +126,16 @@ - (instancetype)initWithNativeInstance:(void *)nativeInstance {
   return self;
 }
 
-- (instancetype)initWithTensor:(ExecuTorchTensor *)otherTensor {
+- (instancetype)initWithTensor:(ExecuTorchTensor *)otherTensor
+                         shape:(NSArray<NSNumber *> *)shape
+                dimensionOrder:(NSArray<NSNumber *> *)dimensionOrder
+                       strides:(NSArray<NSNumber *> *)strides {
   ET_CHECK(otherTensor);
   auto tensor = make_tensor_ptr(
-    *reinterpret_cast<TensorPtr *>(otherTensor.nativeInstance)
+    *reinterpret_cast<TensorPtr *>(otherTensor.nativeInstance),
+    utils::toVector<SizesType>(shape),
+    utils::toVector<DimOrderType>(dimensionOrder),
+    utils::toVector<StridesType>(strides)
   );
   self = [self initWithNativeInstance:&tensor];
   if (self) {
@@ -138,6 +144,21 @@ - (instancetype)initWithTensor:(ExecuTorchTensor *)otherTensor {
   return self;
 }
 
+- (instancetype)initWithTensor:(ExecuTorchTensor *)otherTensor
+                         shape:(NSArray<NSNumber *> *)shape {
+  return [self initWithTensor:otherTensor
+                        shape:shape
+               dimensionOrder:@[]
+                      strides:@[]];
+}
+
+- (instancetype)initWithTensor:(ExecuTorchTensor *)otherTensor {
+  return [self initWithTensor:otherTensor
+                        shape:@[]
+               dimensionOrder:@[]
+                      strides:@[]];
+}
+
 - (instancetype)copy {
   return [self copyWithZone:nil];
 }

extension/apple/ExecuTorch/__tests__/TensorTest.swift

@@ -168,6 +168,38 @@ class TensorTest: XCTestCase {
     XCTAssertEqual(tensor2.count, tensor1.count)
   }
 
+  func testInitWithTensorDerivesStridesAndSharesStorage() {
+    var scalars: [Int32] = [1, 2, 3, 4, 5, 6]
+    let tensor1 = scalars.withUnsafeMutableBytes {
+      Tensor<Int32>(bytesNoCopy: $0.baseAddress!, shape: [2, 3])
+    }
+    let tensor2 = Tensor(tensor1, shape: [3, 2])
+
+    XCTAssertEqual(tensor1.withUnsafeBytes { $0.baseAddress }, tensor2.withUnsafeBytes { $0.baseAddress })
+    XCTAssertEqual(tensor2.shape, [3, 2])
+    XCTAssertEqual(tensor2.strides, [2, 1])
+    XCTAssertEqual(tensor2.dimensionOrder, [0, 1])
+
+    scalars[0] = 99
+    XCTAssertEqual(tensor2.withUnsafeBytes { $0[0] }, 99)
+  }
+
+  func testInitWithTensorExplicitOverridesAppliesMetadata() {
+    var scalars: [Float] = [1, 2, 3, 4]
+    let tensor1 = scalars.withUnsafeMutableBytes {
+      Tensor<Float>(bytesNoCopy: $0.baseAddress!, shape: [2, 2])
+    }
+    let tensor2 = Tensor(tensor1, shape: [2, 2], dimensionOrder: [1, 0], strides: [1, 2])
+
+    XCTAssertEqual(tensor1.withUnsafeBytes { $0.baseAddress }, tensor2.withUnsafeBytes { $0.baseAddress })
+    XCTAssertEqual(tensor2.shape, [2, 2])
+    XCTAssertEqual(tensor2.dimensionOrder, [1, 0])
+    XCTAssertEqual(tensor2.strides, [1, 2])
+
+    scalars[3] = 42
+    XCTAssertEqual(tensor2.withUnsafeBytes { $0[3] }, 42)
+  }
+
   func testCopy() {
     var data: [Double] = [10.0, 20.0, 30.0, 40.0]
     let tensor1 = data.withUnsafeMutableBytes {