Table Of Contents
Table Of Contents

HybridBlock

class mxnet.gluon.nn.HybridBlock(prefix=None, params=None)[source]

HybridBlock supports forwarding with both Symbol and NDArray.

HybridBlock is similar to Block, with a few differences:

import mxnet as mx
from mxnet.gluon import HybridBlock, nn

class Model(HybridBlock):
    def __init__(self, **kwargs):
        super(Model, self).__init__(**kwargs)
        # use name_scope to give child Blocks appropriate names.
        with self.name_scope():
            self.dense0 = nn.Dense(20)
            self.dense1 = nn.Dense(20)

    def hybrid_forward(self, F, x):
        x = F.relu(self.dense0(x))
        return F.relu(self.dense1(x))

model = Model()
model.initialize(ctx=mx.cpu(0))
model.hybridize()
model(mx.nd.zeros((10, 10), ctx=mx.cpu(0)))

Forward computation in HybridBlock must be static to work with Symbol s, i.e. you cannot call NDArray.asnumpy(), NDArray.shape, NDArray.dtype, NDArray indexing (x[i]) etc on tensors. Also, you cannot use branching or loop logic that bases on non-constant expressions like random numbers or intermediate results, since they change the graph structure for each iteration.

Before activating with hybridize(), HybridBlock works just like normal Block. After activation, HybridBlock will create a symbolic graph representing the forward computation and cache it. On subsequent forwards, the cached graph will be used instead of hybrid_forward().

Please see references for detailed tutorial.

References

Hybrid - Faster training and easy deployment

__init__(prefix=None, params=None)[source]

Initialize self. See help(type(self)) for accurate signature.

Methods

__init__([prefix, params]) Initialize self.
apply(fn) Applies fn recursively to every child block as well as self.
cast(dtype) Cast this Block to use another data type.
collect_params([select]) Returns a ParameterDict containing this Block and all of its children’s Parameters(default), also can returns the select ParameterDict which match some given regular expressions.
export(path[, epoch]) Export HybridBlock to json format that can be loaded by SymbolBlock.imports, mxnet.mod.Module or the C++ interface.
forward(x, *args) Defines the forward computation.
hybrid_forward(F, x, *args, **kwargs) Overrides to construct symbolic graph for this Block.
hybridize([active]) Activates or deactivates HybridBlock s recursively.
infer_shape(*args) Infers shape of Parameters from inputs.
infer_type(*args) Infers data type of Parameters from inputs.
initialize([init, ctx, verbose, force_reinit]) Initializes Parameter s of this Block and its children.
load_parameters(filename[, ctx, …]) Load parameters from file previously saved by save_parameters.
load_params(filename[, ctx, allow_missing, …]) [Deprecated] Please use load_parameters.
name_scope() Returns a name space object managing a child Block and parameter names.
register_child(block[, name]) Registers block as a child of self.
register_forward_hook(hook) Registers a forward hook on the block.
register_forward_pre_hook(hook) Registers a forward pre-hook on the block.
save_parameters(filename) Save parameters to file.
save_params(filename) [Deprecated] Please use save_parameters.
summary(*inputs) Print the summary of the model’s output and parameters.

Attributes

name Name of this Block, without ‘_’ in the end.
params Returns this Block’s parameter dictionary (does not include its children’s parameters).
prefix Prefix of this Block.