Computes the mean squared error between the labels and predictions.
The mean_squared_error function creates two local variables, total and count that are used to compute the mean squared error. This average is weighted by weights, and it is ultimately returned as mean_squared_error: an idempotent operation that simply divides total by count.
For estimation of the metric over a stream of data, the function creates an update_op operation that updates these variables and returns the mean_squared_error. Internally, a squared_error operation computes the element-wise square of the difference between predictions and labels. Then update_op increments total with the reduced sum of the product of weights and squared_error, and it increments count with the reduced sum of weights.
metrics_collections: An optional list of collections that mean_squared_error should be added to.
mean_squared_error: A Tensor representing the current mean, the value of total divided by count.
update_op: An operation that increments the total and count variables appropriately and whose value matches mean_squared_error.