Expose Snapshot to pycaffe

- Solver::Snapshot is made public
- It is also added as `snapshot` to pycaffe

Addressing #3077

include/caffe/solver.hpp

@@ -60,6 +60,11 @@ class Solver {
  // RestoreSolverStateFrom___ protected methods. You should implement these
  // methods to restore the state from the appropriate snapshot type.
  void Restore(const char* resume_file);
+ // The Solver::Snapshot function implements the basic snapshotting utility
+ // that stores the learned net. You should implement the SnapshotSolverState()
+ // function that produces a SolverState protocol buffer that needs to be
+ // written to disk together with the learned net.
+ void Snapshot();
  virtual ~Solver() {}
  inline const SolverParameter& param() const { return param_; }
  inline shared_ptr<Net<Dtype> > net() { return net_; }
@@ -87,11 +92,6 @@ class Solver {
  protected:
  // Make and apply the update value for the current iteration.
  virtual void ApplyUpdate() = 0;
- // The Solver::Snapshot function implements the basic snapshotting utility
- // that stores the learned net. You should implement the SnapshotSolverState()
- // function that produces a SolverState protocol buffer that needs to be
- // written to disk together with the learned net.
- void Snapshot();
  string SnapshotFilename(const string extension);
  string SnapshotToBinaryProto();
  string SnapshotToHDF5();

python/caffe/_caffe.cpp

@@ -286,7 +286,8 @@ BOOST_PYTHON_MODULE(_caffe) {
  .def("solve", static_cast<void (Solver<Dtype>::*)(const char*)>(
  &Solver<Dtype>::Solve), SolveOverloads())
  .def("step", &Solver<Dtype>::Step)
- .def("restore", &Solver<Dtype>::Restore);
+ .def("restore", &Solver<Dtype>::Restore)
+ .def("snapshot", &Solver<Dtype>::Snapshot);
 
  bp::class_<SGDSolver<Dtype>, bp::bases<Solver<Dtype> >,
  shared_ptr<SGDSolver<Dtype> >, boost::noncopyable>(