Migrate `erf` and `erf_` from the TH to Aten (CUDA) : Closes #24558 (#36724)
Summary:
Closes https://github.com/pytorch/pytorch/issues/24558
Benchmark with same build settings on same system.
gcc : version 7.5.0 (Ubuntu 7.5.0-3ubuntu1~18.04)
CUDA : 10.1
GPU : 1050ti
```python
import timeit
for n, t in [(10_000, 20000),
(100_000, 20000)]:
for dtype in ('torch.half', 'torch.float', 'torch.double'):
print(f'torch.erf(a) a.numel() == {n} for {t} times {dtype}')
print(timeit.timeit(f'torch.erf(a); torch.cuda.synchronize()',
setup=f'import torch; a=torch.arange({n}, dtype={dtype}, device="cuda")',
number=t))
```
Before:
```
torch.erf(a) a.numel() == 10000 for 20000 times torch.half
0.29057903600187274
torch.erf(a) a.numel() == 10000 for 20000 times torch.float
0.2836507789979805
torch.erf(a) a.numel() == 10000 for 20000 times torch.double
0.44974555500084534
torch.erf(a) a.numel() == 100000 for 20000 times torch.half
0.31807255600142526
torch.erf(a) a.numel() == 100000 for 20000 times torch.float
0.3216503109979385
torch.erf(a) a.numel() == 100000 for 20000 times torch.double
2.0413486910001666
```
After:
```
torch.erf(a) a.numel() == 10000 for 20000 times torch.half
0.2867302739996376
torch.erf(a) a.numel() == 10000 for 20000 times torch.float
0.28851128199858067
torch.erf(a) a.numel() == 10000 for 20000 times torch.double
0.4592030350013374
torch.erf(a) a.numel() == 100000 for 20000 times torch.half
0.28704102400115517
torch.erf(a) a.numel() == 100000 for 20000 times torch.float
0.29036039400125446
torch.erf(a) a.numel() == 100000 for 20000 times torch.double
2.04035638699861
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/36724
Differential Revision: D21164626
Pulled By: VitalyFedyunin
fbshipit-source-id: e6f3390b2bbb6e8d21e18ffe15f5d49a170fae83
