enable Half for cat serial kernel (#96021)
Summary:
1.31 x speedup.
| | shape | before | after |
| ------------ | ------------- | ------------ | ------------- |
| half | 1024 * (100 + i) | 235.75 us | 179.11 us |
Benchmark with
```
import torch
import torch.utils.benchmark as benchmark
def cat(*args, dim=0):
return torch.cat(args, dim)
tensors = []
for i in range(10):
tensors.append(torch.rand(1024, 100 + i).half())
t0 = benchmark.Timer(
stmt="cat(*tensors, dim=1)",
setup="from __main__ import cat",
globals={"tensors": tensors},
num_threads=1,
)
```
Test Plan: CI
Differential Revision: D43810514
Pull Request resolved: https://github.com/pytorch/pytorch/pull/96021
Approved by: https://github.com/ngimel, https://github.com/houseroad, https://github.com/jgong5
