| 48 | } |
| 49 | |
| 50 | bool IsGradNode(const string& name, string* forward_name) { |
| 51 | // Given a forward operation with name op, its gradient op has the following |
| 52 | // name: ...gradients/op_grad/... |
| 53 | // TODO(xpan): This is hacky. |
| 54 | auto grad_prefix = name.find("gradients/"); |
| 55 | auto grad_suffix = name.find("_grad/"); |
| 56 | if (grad_prefix == name.npos || grad_suffix == name.npos) { |
| 57 | return false; |
| 58 | } |
| 59 | auto start = grad_prefix + string("gradients/").length(); |
| 60 | auto len = grad_suffix - start; |
| 61 | if (len <= 0) { |
| 62 | return false; |
| 63 | } |
| 64 | *forward_name = name.substr(start, len); |
| 65 | return true; |
| 66 | } |
| 67 | |
| 68 | // StringTable maps each string to an id. |
| 69 | class StringTable { |