…nged

[ghstack-poisoned]

…d to be changed"

[ghstack-poisoned]

…d to be changed"


Trying a different approach to achieve a performance gain while retaining the ability to do autograd on the results when possible.

```
[<torch.utils.benchmark.utils.common.Measurement object at 0x7f45dd86b070>
x.view(-1);
setup: at::Tensor x=torch::empty({2,2} );
  Median: 583.27 ns
  IQR:    39.04 ns (563.48 to 602.52)
  852 measurements, 10000 runs per measurement, 1 thread]

[<torch.utils.benchmark.utils.common.Measurement object at 0x7f45dd936d30>
x.reshape(-1);
setup: at::Tensor x=torch::empty({2,2} );
  Median: 383.82 ns
  IQR:    19.56 ns (372.88 to 392.45)
  130 measurements, 100000 runs per measurement, 1 thread]

56896
41036

<torch.utils.benchmark.utils.valgrind_wrapper.timer_interface.FunctionCounts object at 0x7f45b138cd00>
    2000  ???:at::native::reshape(at::Tensor const&, c10::ArrayRef<long>)
    1860  ???:torch::autograd::VariableType::(anonymous namespace)::_unsafe_reshape_alias(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)
    1660  ???:at::_ops::_unsafe_reshape_alias::call(at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)
    1600  ???:at::Tensor at::native::alias_with_sizes_and_strides<c10::ArrayRef<long> >(at::Tensor const&, c10::ArrayRef<long> const&, c10::ArrayRef<long> const&)
    1520  ???:at::_ops::reshape::call(at::Tensor const&, c10::ArrayRef<long>)
    1240  ???:at::_ops::_unsafe_reshape_alias::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)
     980  ???:void at::infer_size_impl<c10::SmallVector<long, 5u> >(c10::ArrayRef<long>, long, c10::SmallVector<long, 5u>&)
     520  ???:at::shouldRunRecordFunction(bool*)
     360  ???:c10::TensorImpl::~TensorImpl()
     ...
   -1520  ???:at::_ops::view::call(at::Tensor const&, c10::ArrayRef<long>)
   -1580  ???:torch::ADInplaceOrView::(anonymous namespace)::view(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
   -1640  ???:c10::intrusive_ptr<c10::TensorImpl, c10::UndefinedTensorImpl>::reset_()
   -1680  ???:at::Tensor at::native::alias_with_sizes_and_strides<c10::SmallVector<long, 5u> >(at::Tensor const&, c10::SmallVector<long, 5u> const&, c10::SmallVector<long, 5u> const&)
   -1740  ???:torch::autograd::VariableType::(anonymous namespace)::view(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
   -2080  ???:torch::autograd::make_variable_differentiable_view(at::Tensor const&, c10::optional<torc ... ewInfo>, c10::optional<torch::autograd::ViewInfo>, bool, torch::autograd::CreationMeta, bool)
   -2180  ???:torch::autograd::as_view(at::Tensor const&, at::Tensor const&, bool, bool, std::function<at::Tensor (at::Tensor const&)>, torch::autograd::CreationMeta, bool)
   -2240  ???:torch::autograd::DifferentiableViewMeta::DifferentiableViewMeta(c10::TensorImpl*, c10::o ... ad::ViewInfo>, c10::optional<torch::autograd::ViewInfo>, bool, torch::autograd::CreationMeta)
   -2640  ???:at::native::view(at::Tensor const&, c10::ArrayRef<long>)

Total: -15860
```

[ghstack-poisoned]

…d to be changed"


Trying a different approach to achieve a performance gain while retaining the ability to do autograd on the results when possible.

```
[<torch.utils.benchmark.utils.common.Measurement object at 0x7f45dd86b070>
x.view(-1);
setup: at::Tensor x=torch::empty({2,2} );
  Median: 583.27 ns
  IQR:    39.04 ns (563.48 to 602.52)
  852 measurements, 10000 runs per measurement, 1 thread]

[<torch.utils.benchmark.utils.common.Measurement object at 0x7f45dd936d30>
x.reshape(-1);
setup: at::Tensor x=torch::empty({2,2} );
  Median: 383.82 ns
  IQR:    19.56 ns (372.88 to 392.45)
  130 measurements, 100000 runs per measurement, 1 thread]

56896
41036

<torch.utils.benchmark.utils.valgrind_wrapper.timer_interface.FunctionCounts object at 0x7f45b138cd00>
    2000  ???:at::native::reshape(at::Tensor const&, c10::ArrayRef<long>)
    1860  ???:torch::autograd::VariableType::(anonymous namespace)::_unsafe_reshape_alias(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)
    1660  ???:at::_ops::_unsafe_reshape_alias::call(at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)
    1600  ???:at::Tensor at::native::alias_with_sizes_and_strides<c10::ArrayRef<long> >(at::Tensor const&, c10::ArrayRef<long> const&, c10::ArrayRef<long> const&)
    1520  ???:at::_ops::reshape::call(at::Tensor const&, c10::ArrayRef<long>)
    1240  ???:at::_ops::_unsafe_reshape_alias::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)
     980  ???:void at::infer_size_impl<c10::SmallVector<long, 5u> >(c10::ArrayRef<long>, long, c10::SmallVector<long, 5u>&)
     520  ???:at::shouldRunRecordFunction(bool*)
     360  ???:c10::TensorImpl::~TensorImpl()
     ...
   -1520  ???:at::_ops::view::call(at::Tensor const&, c10::ArrayRef<long>)
   -1580  ???:torch::ADInplaceOrView::(anonymous namespace)::view(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
   -1640  ???:c10::intrusive_ptr<c10::TensorImpl, c10::UndefinedTensorImpl>::reset_()
   -1680  ???:at::Tensor at::native::alias_with_sizes_and_strides<c10::SmallVector<long, 5u> >(at::Tensor const&, c10::SmallVector<long, 5u> const&, c10::SmallVector<long, 5u> const&)
   -1740  ???:torch::autograd::VariableType::(anonymous namespace)::view(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
   -2080  ???:torch::autograd::make_variable_differentiable_view(at::Tensor const&, c10::optional<torc ... ewInfo>, c10::optional<torch::autograd::ViewInfo>, bool, torch::autograd::CreationMeta, bool)
   -2180  ???:torch::autograd::as_view(at::Tensor const&, at::Tensor const&, bool, bool, std::function<at::Tensor (at::Tensor const&)>, torch::autograd::CreationMeta, bool)
   -2240  ???:torch::autograd::DifferentiableViewMeta::DifferentiableViewMeta(c10::TensorImpl*, c10::o ... ad::ViewInfo>, c10::optional<torch::autograd::ViewInfo>, bool, torch::autograd::CreationMeta)
   -2640  ???:at::native::view(at::Tensor const&, c10::ArrayRef<long>)

Total: -15860
```

[ghstack-poisoned]

…d to be changed"


## Goal

Per #55126 the performance of `reshape` is worse than `alias` in cases where they are performing the same operation (i.e. where reshape is returning a view) because `reshape` delegates to `view` and duplicates some of the operations (specifically `infer_size_dv` and `computeStride`).

The goal of this pull-request is to reduce or remove the additional overhead that `reshape` has.

### Proposed Implementation

Instead of using `view` we implement a private/internal operator (`_reshape_alias`) that `reshape` dispatches to which skips the relevant checks. This is functionally equivalent to `as_strided` however it is a lot simpler because it's specialized to this use-case, and importantly the `backward` implementation is a lot faster.

Note that we have to dispatch (`reshape` is a composite operator) because `reshape` can return either a view or a copy of the Tensor depending on the parameters, and this complicates implementing a derivative/backward for `reshape`.

### Why not `as_strided`?

Using `as_strided` directly slows down autograd. If we use a custom function equivalent to `_reshape_alias` but with a simpler backward function then `view` has the same performance as `reshape`. If we delegate to `as_strided` it is about 56% slower (and this holds against our custom function).

This is also the reason we make an internal operator named `_reshape_alias` instead of exposing a new operator since this should only be used in the `reshape` case and it is effectively a more limited version of `view`, `alias`, and `as_strided`.

## Benchmarks
In a micro-benchmark for `backward` running:

```cpp
// Setup
at::Tensor x=torch::empty({2,2}, torch::requires_grad(true));

// Benchmark loop
// `reshape(-1)` replaced with a call to view(-1) for view baseline
x.pow(4).reshape(-1).mean().backward();
```

I also benchmarked simple operations without gradients using:

```cpp
// Setup
at::Tensor x=torch::empty({2,2}, torch::requires_grad(true));

// Benchmark loop
x.reshape(-1) // replaced with a call to view(-1) for view baseline
```

Baselined to `view`:

* Original `reshape`: `+3.3%` (without gradients `+20.8%`)
* Using `as_strided`: `+55.1%` (without gradients `+1.0%`)
* Using custom `_reshape_view`: `-1.0%` (without gradients `+6.2%`)

In absolute terms (note the percentages above were generated comparing between runs/tests rather than to a single baseline):

* Original `view`: `53.66 us` (without gradients `582.78 ns`)
* Original `reshape`: `55.46 us` (without gradients `704.24 ns`)
* Using `as_strided`: `83.24 us` (without gradients `576.49 ns`)
* Using custom `_reshape_view`: `53.13 us` (without gradients `536.01 ns`)

Note that these benchmarks perform a backwards operation as well. When compared without using gradient computation at all the performance differneces are more pronounced as this takes up more of the time.

### Original performance

<details>
  <summary>Benchmark results</summary>

```
[<torch.utils.benchmark.utils.common.Measurement object at 0x7f0e4d393160>
x.pow(4).view(-1).mean().backward();
setup: at::Tensor x=torch::empty({2,2}, torch::requires_grad(true));
  Median: 53.66 us
  IQR:    2.70 us (52.54 to 55.24)
  884 measurements, 100 runs per measurement, 1 thread]

[<torch.utils.benchmark.utils.common.Measurement object at 0x7f0e2ebd4fa0>
x.pow(4).reshape(-1).mean().backward();
setup: at::Tensor x=torch::empty({2,2}, torch::requires_grad(true));
  Median: 55.46 us
  IQR:    2.61 us (54.39 to 57.01)
  889 measurements, 100 runs per measurement, 1 thread]

2276116
2286256

<torch.utils.benchmark.utils.valgrind_wrapper.timer_interface.FunctionCounts object at 0x7f0e5b2e3e20>
   2640  ???:at::detail::computeStride(c10::ArrayRef<long>, c10::ArrayRef<long>, c10::SmallVector<long, 5u> const&)
   1920  ???:at::native::reshape(at::Tensor const&, c10::ArrayRef<long>)
   1520  ???:at::_ops::reshape::call(at::Tensor const&, c10::ArrayRef<long>)
   1040  ???:c10::SmallVectorImpl<long>::operator=(c10::SmallVectorImpl<long>&&)
    980  ???:void at::infer_size_impl<c10::SmallVector<long, 5u> >(c10::ArrayRef<long>, long, c10::SmallVector<long, 5u>&)
    720  ???:__tls_get_addr
    520  ???:at::shouldRunRecordFunction(bool*)
    520  ???:__memcpy_avx_unaligned_erms
    200  ???:c10::impl::wrap_kernel_functor_unboxed_<c10::impl::detail::WrapFunctionIntoFunctor_<c10:: ... g>)>::call(c10::OperatorKernel*, c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
    100  ???:c10::TensorImpl::strides() const
    100  ???:c10::TensorImpl::sizes() const
    100  ???:at::(anonymous namespace)::manager()
     77  /tmp/benchmark_utils_jit_build__1626465284__8a34e7ff-cd37-4a82-be28-7f19e081e771/timer_cpp_7815557938202456331/timer_src.cpp:main
     40  ???:c10::TensorImpl::numel() const
    -77  /tmp/benchmark_utils_jit_build__1626465284__8a34e7ff-cd37-4a82-be28-7f19e081e771/timer_cpp_8055217880649990171/timer_src.cpp:main
   -260  ???:at::native::view(at::Tensor const&, c10::ArrayRef<long>)

Total: 10140
```

```
[<torch.utils.benchmark.utils.common.Measurement object at 0x7f850dd66c10>
x.view(-1);
setup: at::Tensor x=torch::empty({2,2});
  Median: 582.78 ns
  IQR:    33.80 ns (573.80 to 607.61)
  833 measurements, 10000 runs per measurement, 1 thread]

[<torch.utils.benchmark.utils.common.Measurement object at 0x7f850de31e20>
x.reshape(-1);
setup: at::Tensor x=torch::empty({2,2});
  Median: 704.24 ns
  IQR:    24.42 ns (697.20 to 721.62)
  679 measurements, 10000 runs per measurement, 1 thread]

56896
67036

<torch.utils.benchmark.utils.valgrind_wrapper.timer_interface.FunctionCounts object at 0x7f84e1930bb0>
   2640  ???:at::detail::computeStride(c10::ArrayRef<long>, c10::ArrayRef<long>, c10::SmallVector<long, 5u> const&)
   1920  ???:at::native::reshape(at::Tensor const&, c10::ArrayRef<long>)
   1520  ???:at::_ops::reshape::call(at::Tensor const&, c10::ArrayRef<long>)
   1040  ???:c10::SmallVectorImpl<long>::operator=(c10::SmallVectorImpl<long>&&)
    980  ???:void at::infer_size_impl<c10::SmallVector<long, 5u> >(c10::ArrayRef<long>, long, c10::SmallVector<long, 5u>&)
    720  ???:__tls_get_addr
    520  ???:at::shouldRunRecordFunction(bool*)
    520  ???:__memcpy_avx_unaligned_erms
    200  ???:c10::impl::wrap_kernel_functor_unboxed_<c10::impl::detail::WrapFunctionIntoFunctor_<c10:: ... g>)>::call(c10::OperatorKernel*, c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
    100  ???:c10::TensorImpl::strides() const
    100  ???:c10::TensorImpl::sizes() const
    100  ???:at::(anonymous namespace)::manager()
     76  /tmp/benchmark_utils_jit_build__1626466038__15fbbac0-2072-4459-8f8e-08121a905b99/timer_cpp_547407365342278353/timer_src.cpp:main
     40  ???:c10::TensorImpl::numel() const
    -76  /tmp/benchmark_utils_jit_build__1626466038__15fbbac0-2072-4459-8f8e-08121a905b99/timer_cpp_3457873755756181226/timer_src.cpp:main
   -260  ???:at::native::view(at::Tensor const&, c10::ArrayRef<long>)

Total: 10140
```

</details>

### Using `as_strided`

<details>
  <summary>Benchmark results</summary>

```
[<torch.utils.benchmark.utils.common.Measurement object at 0x7f8b13bb5b50>
x.pow(4).view(-1).mean().backward();
setup: at::Tensor x=torch::empty({2,2}, torch::requires_grad(true));
  Median: 53.37 us
  IQR:    3.15 us (51.73 to 54.88)
  936 measurements, 100 runs per measurement, 1 thread]

[<torch.utils.benchmark.utils.common.Measurement object at 0x7f8af55f8490>
x.pow(4).reshape(-1).mean().backward();
setup: at::Tensor x=torch::empty({2,2}, torch::requires_grad(true));
  Median: 83.24 us
  IQR:    4.05 us (81.20 to 85.25)
  609 measurements, 100 runs per measurement, 1 thread]

2267916
2525061

<torch.utils.benchmark.utils.valgrind_wrapper.timer_interface.FunctionCounts object at 0x7f8af55f8e50>
   31930  ???:_int_free
   15940  ???:malloc
   11595  ???:_int_malloc
   10100  ???:torch::autograd::generated::details::as_strided_backward(at::Tensor, at::TensorGeometry, c10::ArrayRef<long>, c10::ArrayRef<long>, c10::optional<long>)
    9360  ???:__tls_get_addr
    8280  ???:free
    8100  ???:torch::autograd::VariableType::(anonymous namespace)::as_strided(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>, c10::optional<long>)
    4520  ???:c10::intrusive_ptr<c10::TensorImpl, c10::UndefinedTensorImpl>::reset_()
    4080  ???:operator new(unsigned long)
     ...
    -780  ???:at::_ops::view::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
    -920  ???:c10::SmallVectorImpl<long>::operator=(c10::SmallVectorImpl<long> const&)
   -1220  ???:torch::autograd::generated::ViewBackward::apply(std::vector<at::Tensor, std::allocator<at::Tensor> >&&)
   -1520  ???:at::_ops::view::call(at::Tensor const&, c10::ArrayRef<long>)
   -1580  ???:torch::ADInplaceOrView::(anonymous namespace)::view(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
   -1680  ???:at::Tensor at::native::alias_with_sizes_and_strides<c10::SmallVector<long, 5u> >(at::Tensor const&, c10::SmallVector<long, 5u> const&, c10::SmallVector<long, 5u> const&)
   -2560  ???:at::detail::computeStride(c10::ArrayRef<long>, c10::ArrayRef<long>, c10::SmallVector<long, 5u> const&)
   -2640  ???:at::native::view(at::Tensor const&, c10::ArrayRef<long>)
   -4860  ???:torch::autograd::VariableType::(anonymous namespace)::view(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)

Total: 257145
```

```

[<torch.utils.benchmark.utils.common.Measurement object at 0x7f93176a0160>
x.view(-1);
setup: at::Tensor x=torch::empty({2,2});
  Median: 570.55 ns
  IQR:    32.69 ns (552.87 to 585.56)
  874 measurements, 10000 runs per measurement, 1 thread]

[<torch.utils.benchmark.utils.common.Measurement object at 0x7f92f8f29490>
x.reshape(-1);
setup: at::Tensor x=torch::empty({2,2});
  Median: 576.49 ns
  IQR:    37.95 ns (559.51 to 597.46)
  861 measurements, 10000 runs per measurement, 1 thread]

56896
58556

<torch.utils.benchmark.utils.valgrind_wrapper.timer_interface.FunctionCounts object at 0x7f932556ca60>
    2140  ???:at::native::reshape(at::Tensor const&, c10::ArrayRef<long>)
    1940  ???:torch::autograd::VariableType::(anonymous namespace)::as_strided(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>, c10::optional<long>)
    1880  ???:torch::ADInplaceOrView::(anonymous namespace)::as_strided(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>, c10::optional<long>)
    1720  ???:at::_ops::as_strided::call(at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>, c10::optional<long>)
    1520  ???:at::_ops::reshape::call(at::Tensor const&, c10::ArrayRef<long>)
    1400  ???:at::native::as_strided_tensorimpl(at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>, c10::optional<long>)
    1260  ???:at::_ops::as_strided::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>, c10::optional<long>)'2
    1260  ???:at::_ops::as_strided::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>, c10::optional<long>)
     980  ???:void at::infer_size_impl<c10::SmallVector<long, 5u> >(c10::ArrayRef<long>, long, c10::SmallVector<long, 5u>&)
     ...
    -620  ???:at::Tensor c10::Dispatcher::redispatch<at::Tensor, at::Tensor const&, c10::ArrayRef<long ... ::ArrayRef<long>)> const&, c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>) const
    -780  ???:at::_ops::view::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)'2
    -780  ???:at::_ops::view::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
    -920  ???:c10::SmallVectorImpl<long>::operator=(c10::SmallVectorImpl<long> const&)
   -1520  ???:at::_ops::view::call(at::Tensor const&, c10::ArrayRef<long>)
   -1580  ???:torch::ADInplaceOrView::(anonymous namespace)::view(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
   -1680  ???:at::Tensor at::native::alias_with_sizes_and_strides<c10::SmallVector<long, 5u> >(at::Tensor const&, c10::SmallVector<long, 5u> const&, c10::SmallVector<long, 5u> const&)
   -1740  ???:torch::autograd::VariableType::(anonymous namespace)::view(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
   -2640  ???:at::native::view(at::Tensor const&, c10::ArrayRef<long>)

Total: 1660

```


</details>

### Using custom function (`_reshape_alias`)

<details>
  <summary>Benchmark results</summary>

```
[<torch.utils.benchmark.utils.common.Measurement object at 0x7f16861d6b50>
x.pow(4).view(-1).mean().backward();
setup: at::Tensor x=torch::empty({2,2}, torch::requires_grad(true));
  Median: 53.50 us
  IQR:    2.64 us (52.32 to 54.96)
  906 measurements, 100 runs per measurement, 1 thread]

[<torch.utils.benchmark.utils.common.Measurement object at 0x7f1667b2ed60>
x.pow(4).reshape(-1).mean().backward();
setup: at::Tensor x=torch::empty({2,2}, torch::requires_grad(true));
  Median: 53.13 us
  IQR:    3.40 us (51.72 to 55.13)
  914 measurements, 100 runs per measurement, 1 thread]

2269736
2273236

<torch.utils.benchmark.utils.valgrind_wrapper.timer_interface.FunctionCounts object at 0x7f1693f8dc10>
    5060  ???:torch::autograd::VariableType::(anonymous namespace)::_reshape_alias(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)
    2000  ???:at::native::reshape(at::Tensor const&, c10::ArrayRef<long>)
    1780  ???:torch::ADInplaceOrView::(anonymous namespace)::_reshape_alias(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)
    1660  ???:at::_ops::_reshape_alias::call(at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)
    1600  ???:at::Tensor at::native::alias_with_sizes_and_strides<c10::ArrayRef<long> >(at::Tensor const&, c10::ArrayRef<long> const&, c10::ArrayRef<long> const&)
    1520  ???:at::_ops::reshape::call(at::Tensor const&, c10::ArrayRef<long>)
    1240  ???:at::_ops::_reshape_alias::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)'2
    1240  ???:at::_ops::_reshape_alias::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)
    1220  ???:torch::autograd::generated::AliasToShapeBackward::apply(std::vector<at::Tensor, std::allocator<at::Tensor> >&&)
     ...
    -780  ???:at::_ops::view::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)'2
    -780  ???:at::_ops::view::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
    -920  ???:c10::SmallVectorImpl<long>::operator=(c10::SmallVectorImpl<long> const&)
   -1220  ???:torch::autograd::generated::ViewBackward::apply(std::vector<at::Tensor, std::allocator<at::Tensor> >&&)
   -1520  ???:at::_ops::view::call(at::Tensor const&, c10::ArrayRef<long>)
   -1580  ???:torch::ADInplaceOrView::(anonymous namespace)::view(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
   -1680  ???:at::Tensor at::native::alias_with_sizes_and_strides<c10::SmallVector<long, 5u> >(at::Tensor const&, c10::SmallVector<long, 5u> const&, c10::SmallVector<long, 5u> const&)
   -2640  ???:at::native::view(at::Tensor const&, c10::ArrayRef<long>)
   -4860  ???:torch::autograd::VariableType::(anonymous namespace)::view(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)

Total: 3500
```

```

[<torch.utils.benchmark.utils.common.Measurement object at 0x7f5287adfb20>
x.view(-1);
setup: at::Tensor x=torch::empty({2,2});
  Median: 505.10 ns
  IQR:    20.04 ns (500.41 to 520.45)
  944 measurements, 10000 runs per measurement, 1 thread]

[<torch.utils.benchmark.utils.common.Measurement object at 0x7f526951b430>
x.reshape(-1);
setup: at::Tensor x=torch::empty({2,2});
  Median: 536.01 ns
  IQR:    17.81 ns (531.34 to 549.16)
  916 measurements, 10000 runs per measurement, 1 thread]

56896
60376

<torch.utils.benchmark.utils.valgrind_wrapper.timer_interface.FunctionCounts object at 0x7f5295896c10>
    2000  ???:at::native::reshape(at::Tensor const&, c10::ArrayRef<long>)
    1860  ???:torch::autograd::VariableType::(anonymous namespace)::_reshape_alias(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)
    1780  ???:torch::ADInplaceOrView::(anonymous namespace)::_reshape_alias(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)
    1660  ???:at::_ops::_reshape_alias::call(at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)
    1600  ???:at::Tensor at::native::alias_with_sizes_and_strides<c10::ArrayRef<long> >(at::Tensor const&, c10::ArrayRef<long> const&, c10::ArrayRef<long> const&)
    1520  ???:at::_ops::reshape::call(at::Tensor const&, c10::ArrayRef<long>)
    1240  ???:at::_ops::_reshape_alias::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)'2
    1240  ???:at::_ops::_reshape_alias::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)
     980  ???:void at::infer_size_impl<c10::SmallVector<long, 5u> >(c10::ArrayRef<long>, long, c10::SmallVector<long, 5u>&)
     ...
    -620  ???:at::Tensor c10::Dispatcher::redispatch<at::Tensor, at::Tensor const&, c10::ArrayRef<long ... ::ArrayRef<long>)> const&, c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>) const
    -780  ???:at::_ops::view::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)'2
    -780  ???:at::_ops::view::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
    -920  ???:c10::SmallVectorImpl<long>::operator=(c10::SmallVectorImpl<long> const&)
   -1520  ???:at::_ops::view::call(at::Tensor const&, c10::ArrayRef<long>)
   -1580  ???:torch::ADInplaceOrView::(anonymous namespace)::view(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
   -1680  ???:at::Tensor at::native::alias_with_sizes_and_strides<c10::SmallVector<long, 5u> >(at::Tensor const&, c10::SmallVector<long, 5u> const&, c10::SmallVector<long, 5u> const&)
   -1740  ???:torch::autograd::VariableType::(anonymous namespace)::view(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
   -2640  ???:at::native::view(at::Tensor const&, c10::ArrayRef<long>)

Total: 3480


```

</details>


[ghstack-poisoned]

…d to be changed"


## Goal

Per #55126 the performance of `reshape` is worse than `alias` in cases where they are performing the same operation (i.e. where reshape is returning a view) because `reshape` delegates to `view` and duplicates some of the operations (specifically `infer_size_dv` and `computeStride`).

The goal of this pull-request is to reduce or remove the additional overhead that `reshape` has.

### Proposed Implementation

Instead of using `view` we implement a private/internal operator (`_reshape_alias`) that `reshape` dispatches to which skips the relevant checks. This is functionally equivalent to `as_strided` however it is a lot simpler because it's specialized to this use-case, and importantly the `backward` implementation is a lot faster.

Note that we have to dispatch (`reshape` is a composite operator) because `reshape` can return either a view or a copy of the Tensor depending on the parameters, and this complicates implementing a derivative/backward for `reshape`.

### Why not `as_strided`?

Using `as_strided` directly slows down autograd. If we use a custom function equivalent to `_reshape_alias` but with a simpler backward function then `view` has the same performance as `reshape`. If we delegate to `as_strided` it is about 56% slower (and this holds against our custom function).

This is also the reason we make an internal operator named `_reshape_alias` instead of exposing a new operator since this should only be used in the `reshape` case and it is effectively a more limited version of `view`, `alias`, and `as_strided`.

## Benchmarks
In a micro-benchmark for `backward` running:

```cpp
// Setup
at::Tensor x=torch::empty({2,2}, torch::requires_grad(true));

// Benchmark loop
// `reshape(-1)` replaced with a call to view(-1) for view baseline
x.pow(4).reshape(-1).mean().backward();
```

I also benchmarked simple operations without gradients using:

```cpp
// Setup
at::Tensor x=torch::empty({2,2}, torch::requires_grad(true));

// Benchmark loop
x.reshape(-1) // replaced with a call to view(-1) for view baseline
```

Baselined to `view`:

* Original `reshape`: `+3.3%` (without gradients `+20.8%`)
* Using `as_strided`: `+55.1%` (without gradients `+1.0%`)
* Using custom `_reshape_view`: `-1.0%` (without gradients `+6.2%`)

In absolute terms (note the percentages above were generated comparing between runs/tests rather than to a single baseline):

* Original `view`: `53.66 us` (without gradients `582.78 ns`)
* Original `reshape`: `55.46 us` (without gradients `704.24 ns`)
* Using `as_strided`: `83.24 us` (without gradients `576.49 ns`)
* Using custom `_reshape_view`: `53.13 us` (without gradients `536.01 ns`)

Note that these benchmarks perform a backwards operation as well. When compared without using gradient computation at all the performance differneces are more pronounced as this takes up more of the time.

### Original performance

<details>
  <summary>Benchmark results</summary>

```
[<torch.utils.benchmark.utils.common.Measurement object at 0x7f0e4d393160>
x.pow(4).view(-1).mean().backward();
setup: at::Tensor x=torch::empty({2,2}, torch::requires_grad(true));
  Median: 53.66 us
  IQR:    2.70 us (52.54 to 55.24)
  884 measurements, 100 runs per measurement, 1 thread]

[<torch.utils.benchmark.utils.common.Measurement object at 0x7f0e2ebd4fa0>
x.pow(4).reshape(-1).mean().backward();
setup: at::Tensor x=torch::empty({2,2}, torch::requires_grad(true));
  Median: 55.46 us
  IQR:    2.61 us (54.39 to 57.01)
  889 measurements, 100 runs per measurement, 1 thread]

2276116
2286256

<torch.utils.benchmark.utils.valgrind_wrapper.timer_interface.FunctionCounts object at 0x7f0e5b2e3e20>
   2640  ???:at::detail::computeStride(c10::ArrayRef<long>, c10::ArrayRef<long>, c10::SmallVector<long, 5u> const&)
   1920  ???:at::native::reshape(at::Tensor const&, c10::ArrayRef<long>)
   1520  ???:at::_ops::reshape::call(at::Tensor const&, c10::ArrayRef<long>)
   1040  ???:c10::SmallVectorImpl<long>::operator=(c10::SmallVectorImpl<long>&&)
    980  ???:void at::infer_size_impl<c10::SmallVector<long, 5u> >(c10::ArrayRef<long>, long, c10::SmallVector<long, 5u>&)
    720  ???:__tls_get_addr
    520  ???:at::shouldRunRecordFunction(bool*)
    520  ???:__memcpy_avx_unaligned_erms
    200  ???:c10::impl::wrap_kernel_functor_unboxed_<c10::impl::detail::WrapFunctionIntoFunctor_<c10:: ... g>)>::call(c10::OperatorKernel*, c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
    100  ???:c10::TensorImpl::strides() const
    100  ???:c10::TensorImpl::sizes() const
    100  ???:at::(anonymous namespace)::manager()
     77  /tmp/benchmark_utils_jit_build__1626465284__8a34e7ff-cd37-4a82-be28-7f19e081e771/timer_cpp_7815557938202456331/timer_src.cpp:main
     40  ???:c10::TensorImpl::numel() const
    -77  /tmp/benchmark_utils_jit_build__1626465284__8a34e7ff-cd37-4a82-be28-7f19e081e771/timer_cpp_8055217880649990171/timer_src.cpp:main
   -260  ???:at::native::view(at::Tensor const&, c10::ArrayRef<long>)

Total: 10140
```

```
[<torch.utils.benchmark.utils.common.Measurement object at 0x7f850dd66c10>
x.view(-1);
setup: at::Tensor x=torch::empty({2,2});
  Median: 582.78 ns
  IQR:    33.80 ns (573.80 to 607.61)
  833 measurements, 10000 runs per measurement, 1 thread]

[<torch.utils.benchmark.utils.common.Measurement object at 0x7f850de31e20>
x.reshape(-1);
setup: at::Tensor x=torch::empty({2,2});
  Median: 704.24 ns
  IQR:    24.42 ns (697.20 to 721.62)
  679 measurements, 10000 runs per measurement, 1 thread]

56896
67036

<torch.utils.benchmark.utils.valgrind_wrapper.timer_interface.FunctionCounts object at 0x7f84e1930bb0>
   2640  ???:at::detail::computeStride(c10::ArrayRef<long>, c10::ArrayRef<long>, c10::SmallVector<long, 5u> const&)
   1920  ???:at::native::reshape(at::Tensor const&, c10::ArrayRef<long>)
   1520  ???:at::_ops::reshape::call(at::Tensor const&, c10::ArrayRef<long>)
   1040  ???:c10::SmallVectorImpl<long>::operator=(c10::SmallVectorImpl<long>&&)
    980  ???:void at::infer_size_impl<c10::SmallVector<long, 5u> >(c10::ArrayRef<long>, long, c10::SmallVector<long, 5u>&)
    720  ???:__tls_get_addr
    520  ???:at::shouldRunRecordFunction(bool*)
    520  ???:__memcpy_avx_unaligned_erms
    200  ???:c10::impl::wrap_kernel_functor_unboxed_<c10::impl::detail::WrapFunctionIntoFunctor_<c10:: ... g>)>::call(c10::OperatorKernel*, c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
    100  ???:c10::TensorImpl::strides() const
    100  ???:c10::TensorImpl::sizes() const
    100  ???:at::(anonymous namespace)::manager()
     76  /tmp/benchmark_utils_jit_build__1626466038__15fbbac0-2072-4459-8f8e-08121a905b99/timer_cpp_547407365342278353/timer_src.cpp:main
     40  ???:c10::TensorImpl::numel() const
    -76  /tmp/benchmark_utils_jit_build__1626466038__15fbbac0-2072-4459-8f8e-08121a905b99/timer_cpp_3457873755756181226/timer_src.cpp:main
   -260  ???:at::native::view(at::Tensor const&, c10::ArrayRef<long>)

Total: 10140
```

</details>

### Using `as_strided`

<details>
  <summary>Benchmark results</summary>

```
[<torch.utils.benchmark.utils.common.Measurement object at 0x7f8b13bb5b50>
x.pow(4).view(-1).mean().backward();
setup: at::Tensor x=torch::empty({2,2}, torch::requires_grad(true));
  Median: 53.37 us
  IQR:    3.15 us (51.73 to 54.88)
  936 measurements, 100 runs per measurement, 1 thread]

[<torch.utils.benchmark.utils.common.Measurement object at 0x7f8af55f8490>
x.pow(4).reshape(-1).mean().backward();
setup: at::Tensor x=torch::empty({2,2}, torch::requires_grad(true));
  Median: 83.24 us
  IQR:    4.05 us (81.20 to 85.25)
  609 measurements, 100 runs per measurement, 1 thread]

2267916
2525061

<torch.utils.benchmark.utils.valgrind_wrapper.timer_interface.FunctionCounts object at 0x7f8af55f8e50>
   31930  ???:_int_free
   15940  ???:malloc
   11595  ???:_int_malloc
   10100  ???:torch::autograd::generated::details::as_strided_backward(at::Tensor, at::TensorGeometry, c10::ArrayRef<long>, c10::ArrayRef<long>, c10::optional<long>)
    9360  ???:__tls_get_addr
    8280  ???:free
    8100  ???:torch::autograd::VariableType::(anonymous namespace)::as_strided(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>, c10::optional<long>)
    4520  ???:c10::intrusive_ptr<c10::TensorImpl, c10::UndefinedTensorImpl>::reset_()
    4080  ???:operator new(unsigned long)
     ...
    -780  ???:at::_ops::view::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
    -920  ???:c10::SmallVectorImpl<long>::operator=(c10::SmallVectorImpl<long> const&)
   -1220  ???:torch::autograd::generated::ViewBackward::apply(std::vector<at::Tensor, std::allocator<at::Tensor> >&&)
   -1520  ???:at::_ops::view::call(at::Tensor const&, c10::ArrayRef<long>)
   -1580  ???:torch::ADInplaceOrView::(anonymous namespace)::view(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
   -1680  ???:at::Tensor at::native::alias_with_sizes_and_strides<c10::SmallVector<long, 5u> >(at::Tensor const&, c10::SmallVector<long, 5u> const&, c10::SmallVector<long, 5u> const&)
   -2560  ???:at::detail::computeStride(c10::ArrayRef<long>, c10::ArrayRef<long>, c10::SmallVector<long, 5u> const&)
   -2640  ???:at::native::view(at::Tensor const&, c10::ArrayRef<long>)
   -4860  ???:torch::autograd::VariableType::(anonymous namespace)::view(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)

Total: 257145
```

```

[<torch.utils.benchmark.utils.common.Measurement object at 0x7f93176a0160>
x.view(-1);
setup: at::Tensor x=torch::empty({2,2});
  Median: 570.55 ns
  IQR:    32.69 ns (552.87 to 585.56)
  874 measurements, 10000 runs per measurement, 1 thread]

[<torch.utils.benchmark.utils.common.Measurement object at 0x7f92f8f29490>
x.reshape(-1);
setup: at::Tensor x=torch::empty({2,2});
  Median: 576.49 ns
  IQR:    37.95 ns (559.51 to 597.46)
  861 measurements, 10000 runs per measurement, 1 thread]

56896
58556

<torch.utils.benchmark.utils.valgrind_wrapper.timer_interface.FunctionCounts object at 0x7f932556ca60>
    2140  ???:at::native::reshape(at::Tensor const&, c10::ArrayRef<long>)
    1940  ???:torch::autograd::VariableType::(anonymous namespace)::as_strided(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>, c10::optional<long>)
    1880  ???:torch::ADInplaceOrView::(anonymous namespace)::as_strided(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>, c10::optional<long>)
    1720  ???:at::_ops::as_strided::call(at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>, c10::optional<long>)
    1520  ???:at::_ops::reshape::call(at::Tensor const&, c10::ArrayRef<long>)
    1400  ???:at::native::as_strided_tensorimpl(at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>, c10::optional<long>)
    1260  ???:at::_ops::as_strided::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>, c10::optional<long>)'2
    1260  ???:at::_ops::as_strided::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>, c10::optional<long>)
     980  ???:void at::infer_size_impl<c10::SmallVector<long, 5u> >(c10::ArrayRef<long>, long, c10::SmallVector<long, 5u>&)
     ...
    -620  ???:at::Tensor c10::Dispatcher::redispatch<at::Tensor, at::Tensor const&, c10::ArrayRef<long ... ::ArrayRef<long>)> const&, c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>) const
    -780  ???:at::_ops::view::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)'2
    -780  ???:at::_ops::view::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
    -920  ???:c10::SmallVectorImpl<long>::operator=(c10::SmallVectorImpl<long> const&)
   -1520  ???:at::_ops::view::call(at::Tensor const&, c10::ArrayRef<long>)
   -1580  ???:torch::ADInplaceOrView::(anonymous namespace)::view(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
   -1680  ???:at::Tensor at::native::alias_with_sizes_and_strides<c10::SmallVector<long, 5u> >(at::Tensor const&, c10::SmallVector<long, 5u> const&, c10::SmallVector<long, 5u> const&)
   -1740  ???:torch::autograd::VariableType::(anonymous namespace)::view(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
   -2640  ???:at::native::view(at::Tensor const&, c10::ArrayRef<long>)

Total: 1660

```


</details>

### Using custom function (`_reshape_alias`)

<details>
  <summary>Benchmark results</summary>

```
[<torch.utils.benchmark.utils.common.Measurement object at 0x7f16861d6b50>
x.pow(4).view(-1).mean().backward();
setup: at::Tensor x=torch::empty({2,2}, torch::requires_grad(true));
  Median: 53.50 us
  IQR:    2.64 us (52.32 to 54.96)
  906 measurements, 100 runs per measurement, 1 thread]

[<torch.utils.benchmark.utils.common.Measurement object at 0x7f1667b2ed60>
x.pow(4).reshape(-1).mean().backward();
setup: at::Tensor x=torch::empty({2,2}, torch::requires_grad(true));
  Median: 53.13 us
  IQR:    3.40 us (51.72 to 55.13)
  914 measurements, 100 runs per measurement, 1 thread]

2269736
2273236

<torch.utils.benchmark.utils.valgrind_wrapper.timer_interface.FunctionCounts object at 0x7f1693f8dc10>
    5060  ???:torch::autograd::VariableType::(anonymous namespace)::_reshape_alias(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)
    2000  ???:at::native::reshape(at::Tensor const&, c10::ArrayRef<long>)
    1780  ???:torch::ADInplaceOrView::(anonymous namespace)::_reshape_alias(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)
    1660  ???:at::_ops::_reshape_alias::call(at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)
    1600  ???:at::Tensor at::native::alias_with_sizes_and_strides<c10::ArrayRef<long> >(at::Tensor const&, c10::ArrayRef<long> const&, c10::ArrayRef<long> const&)
    1520  ???:at::_ops::reshape::call(at::Tensor const&, c10::ArrayRef<long>)
    1240  ???:at::_ops::_reshape_alias::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)'2
    1240  ???:at::_ops::_reshape_alias::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)
    1220  ???:torch::autograd::generated::AliasToShapeBackward::apply(std::vector<at::Tensor, std::allocator<at::Tensor> >&&)
     ...
    -780  ???:at::_ops::view::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)'2
    -780  ???:at::_ops::view::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
    -920  ???:c10::SmallVectorImpl<long>::operator=(c10::SmallVectorImpl<long> const&)
   -1220  ???:torch::autograd::generated::ViewBackward::apply(std::vector<at::Tensor, std::allocator<at::Tensor> >&&)
   -1520  ???:at::_ops::view::call(at::Tensor const&, c10::ArrayRef<long>)
   -1580  ???:torch::ADInplaceOrView::(anonymous namespace)::view(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
   -1680  ???:at::Tensor at::native::alias_with_sizes_and_strides<c10::SmallVector<long, 5u> >(at::Tensor const&, c10::SmallVector<long, 5u> const&, c10::SmallVector<long, 5u> const&)
   -2640  ???:at::native::view(at::Tensor const&, c10::ArrayRef<long>)
   -4860  ???:torch::autograd::VariableType::(anonymous namespace)::view(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)

Total: 3500
```

```

[<torch.utils.benchmark.utils.common.Measurement object at 0x7f5287adfb20>
x.view(-1);
setup: at::Tensor x=torch::empty({2,2});
  Median: 505.10 ns
  IQR:    20.04 ns (500.41 to 520.45)
  944 measurements, 10000 runs per measurement, 1 thread]

[<torch.utils.benchmark.utils.common.Measurement object at 0x7f526951b430>
x.reshape(-1);
setup: at::Tensor x=torch::empty({2,2});
  Median: 536.01 ns
  IQR:    17.81 ns (531.34 to 549.16)
  916 measurements, 10000 runs per measurement, 1 thread]

56896
60376

<torch.utils.benchmark.utils.valgrind_wrapper.timer_interface.FunctionCounts object at 0x7f5295896c10>
    2000  ???:at::native::reshape(at::Tensor const&, c10::ArrayRef<long>)
    1860  ???:torch::autograd::VariableType::(anonymous namespace)::_reshape_alias(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)
    1780  ???:torch::ADInplaceOrView::(anonymous namespace)::_reshape_alias(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)
    1660  ???:at::_ops::_reshape_alias::call(at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)
    1600  ???:at::Tensor at::native::alias_with_sizes_and_strides<c10::ArrayRef<long> >(at::Tensor const&, c10::ArrayRef<long> const&, c10::ArrayRef<long> const&)
    1520  ???:at::_ops::reshape::call(at::Tensor const&, c10::ArrayRef<long>)
    1240  ???:at::_ops::_reshape_alias::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)'2
    1240  ???:at::_ops::_reshape_alias::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>, c10::ArrayRef<long>)
     980  ???:void at::infer_size_impl<c10::SmallVector<long, 5u> >(c10::ArrayRef<long>, long, c10::SmallVector<long, 5u>&)
     ...
    -620  ???:at::Tensor c10::Dispatcher::redispatch<at::Tensor, at::Tensor const&, c10::ArrayRef<long ... ::ArrayRef<long>)> const&, c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>) const
    -780  ???:at::_ops::view::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)'2
    -780  ???:at::_ops::view::redispatch(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
    -920  ???:c10::SmallVectorImpl<long>::operator=(c10::SmallVectorImpl<long> const&)
   -1520  ???:at::_ops::view::call(at::Tensor const&, c10::ArrayRef<long>)
   -1580  ???:torch::ADInplaceOrView::(anonymous namespace)::view(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
   -1680  ???:at::Tensor at::native::alias_with_sizes_and_strides<c10::SmallVector<long, 5u> >(at::Tensor const&, c10::SmallVector<long, 5u> const&, c10::SmallVector<long, 5u> const&)
   -1740  ???:torch::autograd::VariableType::(anonymous namespace)::view(c10::DispatchKeySet, at::Tensor const&, c10::ArrayRef<long>)
   -2640  ???:at::native::view(at::Tensor const&, c10::ArrayRef<long>)

Total: 3480


```

</details>


[ghstack-poisoned]