[GitHub] [incubator-tvm] kongroo opened a new pull request #6349: [CODEGEN][CUDA]: fix cuda half math function is undefined: herf

[GitBox]

kongroo opened a new pull request #6349:
URL: https://github.com/apache/incubator-tvm/pull/6349


   I got an "identifier herf undefined" error when converting a model into TVM, 
which can be reproduced by the following code
   ```
   import torch
   import numpy as np
   import tvm
   from tvm import relay
   
   class ErfTest(torch.nn.Module):
       def forward(self, data):
           return torch.erf(data)
   
   def run(data):
       # convert pytorch to tvm
       traced = torch.jit.trace(ErfTest(), torch.from_numpy(data).cuda())
       mod, params = relay.frontend.from_pytorch(traced, [('data', data.shape)])
   
       # compile
       with tvm.transform.PassContext(opt_level=3):
           relay_graph, relay_lib, relay_params = tvm.relay.build(mod, 
target='cuda', params=params)
           relay_model = tvm.contrib.graph_runtime.create(relay_graph, 
relay_lib, tvm.context('gpu', 0))
   
       # run
       relay_model.set_input('data', data)
       relay_model.run()
       return relay_model.get_output(0)
   
   data = np.random.rand(3, 4).astype(np.float32)
   print(torch.erf(torch.Tensor(data)))
   print(run(data))
   print(run(data.astype(np.float16)))
   ```
   
![image](https://user-images.githubusercontent.com/16698151/91425664-04197a00-e88e-11ea-8212-5e08ec9b4650.png)
   
   I fixed this in the same way as #6225 and the results seem ok
   
   <img 
src="https://user-images.githubusercontent.com/16698151/91427276-3deb8000-e890-11ea-8fa0-2fb0c3585cae.png";
 width="300">
   
   cc @vinx13 Could you help to review this?


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