# Stochastic Computation Graph Helper Functions

### tf.contrib.bayesflow.stochastic_graph.surrogate_loss(sample_losses, stochastic_tensors=None, name='SurrogateLoss')

Surrogate loss for stochastic graphs.

This function will call loss_fn on each StochasticTensor upstream of sample_losses, passing the losses that it influenced.

Note that currently surrogate_loss does not work with StochasticTensors instantiated in while_loops or other control structures.

##### Args:
• sample_losses: a list or tuple of final losses. Each loss should be per example in the batch (and possibly per sample); that is, it should have dimensionality of 1 or greater. All losses should have the same shape.
• stochastic_tensors: a list of StochasticTensors to add loss terms for. If None, defaults to all StochasticTensors in the graph upstream of the Tensors in sample_losses.
• name: the name with which to prepend created ops.
##### Returns:

Tensor loss, which is the sum of sample_losses and the loss_fns returned by the StochasticTensors.

##### Raises:
• TypeError: if sample_losses is not a list or tuple, or if its elements are not Tensors.
• ValueError: if any loss in sample_losses does not have dimensionality 1 or greater.