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Returns private cumulative sums by clipping and adding correlated noise.
Inherits From: SumAggregationDPQuery
, DPQuery
tf_privacy.TreeCumulativeSumQuery(
record_specs, noise_generator, clip_fn, clip_value, use_efficient=True
)
Consider calling get_noised_result
T times, and each (x_i, i=0,2,...,T1) is
the private value returned by accumulate_record
, i.e. xi = sum{j=0}^{n1}
x{i,j} where each x{i,j} is a private record in the database. This class is
intended to make multiple queries, which release privatized values of the
cumulative sums si = sum{k=0}^{i} x_k, for i=0,...,T1.
Each call to get_noised_result
releases the next cumulative sum s_i, which
is in contrast to the GaussianSumQuery that releases x_i. Noise for the
cumulative sums is accomplished using the tree aggregation logic in
tree_aggregation
, which is proportional to log(T).
Example usage:
query = TreeCumulativeSumQuery(...) global_state = query.initial_global_state() params = query.derive_sample_params(global_state) for i, samples in enumerate(streaming_samples): sample_state = query.initial_sample_state(samples[0]) # Compute xi = sum{j=0}^{n1} x_{i,j} for j,sample in enumerate(samples): sample_state = query.accumulate_record(params, sample_state, sample) # noised_cumsum is privatized estimate of s_i noised_cumsum, global_state, event = query.get_noised_result( sample_state, global_state)
Args  

record_specs

A nested structure of tf.TensorSpec s specifying structure
and shapes of records.

noise_generator

tree_aggregation.ValueGenerator to generate the noise
value for a tree node. Should be coupled with clipping norm to guarantee
privacy.

clip_fn

Callable that specifies clipping function. Input to clip is a flat list of vars in a record. 
clip_value

Float indicating the value at which to clip the record. 
use_efficient

Boolean indicating the usage of the efficient tree aggregation algorithm based on the paper "Efficient Use of Differentially Private Binary Trees". 
Attributes  

clip_fn

Callable that specifies clipping function. clip_fn receives two
arguments: a flat list of vars in a record and a clip_value to clip the
corresponding record, e.g. clip_fn(flat_record, clip_value).

clip_value

float indicating the value at which to clip the record. 
record_specs

Collection[tf.TensorSpec] specifying shapes of records.

tree_aggregator

tree_aggregation.TreeAggregator initialized with user
defined noise_generator . noise_generator is a
tree_aggregation.ValueGenerator to generate the noise value for a tree
node. Noise stdandard deviation is specified outside the dp_query by the
user when defining noise_fn and should have order
O(clip_norm*log(T)/eps) to guarantee epsDP.

Child Classes
Methods
accumulate_preprocessed_record
accumulate_preprocessed_record(
sample_state, preprocessed_record
)
Implements tensorflow_privacy.DPQuery.accumulate_preprocessed_record
.
accumulate_record
accumulate_record(
params, sample_state, record
)
Accumulates a single record into the sample state.
This is a helper method that simply delegates to preprocess_record
and
accumulate_preprocessed_record
for the common case when both of those
functions run on a single device. Typically this will be a simple sum.
Args  

params

The parameters for the sample. In standard DPSGD training, the clipping norm for the sample's microbatch gradients (i.e., a maximum norm magnitude to which each gradient is clipped) 
sample_state

The current sample state. In standard DPSGD training, the accumulated sum of previous clipped microbatch gradients. 
record

The record to accumulate. In standard DPSGD training, the gradient computed for the examples in one microbatch, which may be the gradient for just one example (for size 1 microbatches). 
Returns  

The updated sample state. In standard DPSGD training, the set of previous microbatch gradients with the addition of the record argument. 
build_l2_gaussian_query
@classmethod
build_l2_gaussian_query( clip_norm, noise_multiplier, record_specs, noise_seed=None, use_efficient=True )
Returns a query instance with L2 norm clipping and Gaussian noise.
Args  

clip_norm

Each record will be clipped so that it has L2 norm at most
clip_norm .

noise_multiplier

The effective noise multiplier for the sum of records.
Noise standard deviation is clip_norm*noise_multiplier .

record_specs

A nested structure of tf.TensorSpec s specifying structure
and shapes of records.

noise_seed

Integer seed for the Gaussian noise generator. If None , a
nondeterministic seed based on system time will be generated.

use_efficient

Boolean indicating the usage of the efficient tree aggregation algorithm based on the paper "Efficient Use of Differentially Private Binary Trees". 
derive_metrics
derive_metrics(
global_state
)
Derives metric information from the current global state.
Any metrics returned should be derived only from privatized quantities.
Args  

global_state

The global state from which to derive metrics. 
Returns  

A collections.OrderedDict mapping string metric names to tensor values.

derive_sample_params
derive_sample_params(
global_state
)
Implements tensorflow_privacy.DPQuery.derive_sample_params
.
get_noised_result
get_noised_result(
sample_state, global_state
)
Implements tensorflow_privacy.DPQuery.get_noised_result
.
Updates tree state, and returns noised cumulative sum and updated state.
Computes new cumulative sum, and returns its noised value. Grows tree state by one new leaf, and returns the new state.
Args  

sample_state

Sum of clipped records for this round. 
global_state

Global state with current sample's cumulative sum and tree state. 
Returns  

A tuple of (noised_cumulative_sum, new_global_state). 
initial_global_state
initial_global_state()
Implements tensorflow_privacy.DPQuery.initial_global_state
.
initial_sample_state
initial_sample_state(
template=None
)
Implements tensorflow_privacy.DPQuery.initial_sample_state
.
merge_sample_states
merge_sample_states(
sample_state_1, sample_state_2
)
Implements tensorflow_privacy.DPQuery.merge_sample_states
.
preprocess_record
preprocess_record(
params, record
)
Implements tensorflow_privacy.DPQuery.preprocess_record
.
Args  

params

clip_value for the record.

record

The record to be processed. 
Returns  

Structure of clipped tensors. 
reset_state
reset_state(
noised_results, global_state
)
Returns state after resetting the tree.
This function will be used in restart_query.RestartQuery
after calling
get_noised_result
when the restarting condition is met.
Args  

noised_results

Noised cumulative sum returned by get_noised_result .

global_state

Updated global state returned by get_noised_result , which
has current sample's cumulative sum and tree state for the next
cumulative sum.

Returns  

New global state with current noised cumulative sum and restarted tree state for the next cumulative sum. 