mureva opened a new issue #18221:
URL: https://github.com/apache/incubator-mxnet/issues/18221
I'm a little lost on using a custom loss function and would appreciate some
help.
I have a network which is doing some regression and have been using the
MAERegressionOutput with some success.
net = CreateNetwork( ... )
lossNet = MAERegressionOutput( "maeLoss", net, idealResult );
When I use MAERegressionOutput things are fairly simple, we just do
1) bind: auto *exec = lossNet.SimpleBind(ctx, args);
2) upload input batch data to the right arrays.
3) forward pass: exec->Forward(true);
4) backward pass: exec->Backward();
If I want metrics on that batch, or to visualise the result of that batch, I
can just get the outputs from exec:
mx::NDArray ND = exec->outputs[0].Copy( mx::Context::cpu() );
These outputs would be the same whether I use lossNet or just net. But what
about when I use a custom loss? I had understood that if I wanted to have both
the output of the custom loss and the output of the network then I would need
to use the Group method:
net = CreateNetwork( ... )
lossNet = Group( { MakeLoss( MyCustomLoss( net, idealData ) ), net } )
And indeed, if I do that then exec->outputs has two symbols of the sizes I
would expect.
However, I'm a little unclear on how to perform the backward pass.
exec->Backward(); This just gives an error complaining about grad_heads,
but
exec->Backward(exec->outputs[0]); is not syntactically correct.
What should I be giving to exec->Backward?
----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
For queries about this service, please contact Infrastructure at:
[email protected]
