def transform(counts):
aligned_counts = lt.select(
total_counts, {'target': list(counts.axes['target'].labels)})
return counts / lt.cast(aligned_counts, tf.float32)
def transform(counts): return lt.cast(counts >= float(threshold), tf.float32)
def upsample_positives(feature_tensors,
count_names,
total_reads_defining_positive,
min_fraction_positive,
seed=None):
"""Returns feature tensors with positives upsampled to the desired rate.
Args:
feature_tensors: Dict[str, lt.LabeledTensor] with parsed featured created by
`build_features`.
count_names: A list of labels that are count names.
total_reads_defining_positive: The minimum number of reads detected across
all conditions that defines a sequence as being a positive example.
min_fraction_positive: The minimum fraction of positive examples to allow
in the data.
seed: The random seed to use in upsampling.
Returns:
A dictionary mapping from string feature name to lt.LabeledTensor of parsed
features created by `build_features` and positive examples upsampled to the
desired rate.
Raises:
ValueError: The minimum positive fraction requested is invalid.
"""
# Goal: Find the fraction of all input feature tensors that should be
# classified as "positive" based on the total_reads_defining_positive.
# Upsample those using resample.resample_at_rate() until they are at least
# min_fraction_positive of the entire set.
if min_fraction_positive < 0 or min_fraction_positive >= 1:
raise ValueError('Invalid fraction positive, must be in [0, 1): %s' %
min_fraction_positive)
with tf.name_scope('upsample_positives'):
# Classify the inputs as positive or negative.
total_reads_defining_positive = tf.constant(
total_reads_defining_positive, dtype=tf.float32)
min_fraction_positive = tf.constant(min_fraction_positive,
dtype=tf.float32)
counts = lt.pack(
[lt.cast(feature_tensors[k], tf.float32) for k in count_names],
('sequence_counts', count_names),
axis_position=1)
greater_equal = (lt.reduce_sum(counts, 'sequence_counts') >=
total_reads_defining_positive)
num_pos = lt.reduce_sum(lt.cast(greater_equal, tf.int32))
less_than = lt.logical_not(greater_equal)
num_neg = lt.reduce_sum(lt.cast(less_than, tf.int32))
# With an initial number of positives P and number of negatives N,
# if we keep the negative sampling rate at 1 (to try to retain negatives),
# to achieve a total positive input fraction of F, we need a positive
# sampling rate R that satisfies:
# P * R / (P * R + N) >= F
#
# Solving for R:
#
# P * R = F * (P*R + N) = F*P*R + F*N
# P * R (1 - F) = F * N
# R = F*N / (P * (1 - F))
numerator = min_fraction_positive * tf.cast(num_neg, tf.float32)
denom = tf.cast(num_pos, tf.float32) * (1 - min_fraction_positive)
denom = tf.cond(
denom > 0.0,
lambda: denom,
# If denom == 0, we can set it to anything we want since the
# tf.cond below is guaranteed to return the input without
# resampling.
lambda: tf.constant(1.0, dtype=tf.float32))
positive_rate = numerator / denom
batch_size = tf.shape(greater_equal)[0]
negative_rates = tf.ones([batch_size], tf.float32)
positive_rates = tf.fill([batch_size], positive_rate)
rates = tf.where(greater_equal, positive_rates, negative_rates)
# Pack the LabeledTensors into normal tensors, keeping relevant information
# for unpacking back to LabeledTensors available.
ordered_names = sorted(feature_tensors)
packed_tensors = []
tensor_axes = []
tensor_shapes = []
for name in ordered_names:
labeled_tensor = feature_tensors[name]
packed_tensors.append(labeled_tensor.tensor)
tensor_axes.append(labeled_tensor.axes)
tensor_shapes.append(labeled_tensor.get_shape())
# Perform the resampling.
resampled_tensors = tf.cond(
tf.logical_or(
tf.equal(num_pos, 0),
tf.cast(num_pos, dtype=tf.float32) >=
(min_fraction_positive *
tf.cast(batch_size, dtype=tf.float32))),
lambda: packed_tensors, lambda: resample.resample_at_rate(
packed_tensors, rates, seed=seed))
# Unpack the tensors into a dictionary of LabeledTensors again.
# First, change the shape so that the batch axis is unknown.
tensor_shapes = [[None] + list(shape)[1:] for shape in tensor_shapes]
for tensor, shape in zip(resampled_tensors, tensor_shapes):
tensor.set_shape(shape)
unpacked_feature_tensors = {}
for i, name in enumerate(ordered_names):
labeled = lt.LabeledTensor(resampled_tensors[i], tensor_axes[i])
unpacked_feature_tensors[name] = labeled
return unpacked_feature_tensors
def create_input_and_outputs(feature_tensors,
experiment_proto,
input_features=(SEQUENCE_ONE_HOT, ),
skip_all_zero_counts=True,
kmer_k_max=4,
additional_output=None):
"""Create inputs and outputs from parsed features.
Args:
feature_tensors: Dict[str, tf.Tensor] with parsed featured created by
`build_features`.
experiment_proto: selection_pb2.Experiment describing the experiment.
input_features: optional sequence of feature constants defined in this
module.
skip_all_zero_counts: some sequences have no counts, e.g., because they were
created artificially for validation purposes on the binding array. We want
to skip these sequences for training.
kmer_k_max: optional integer giving the maximum kmer length to use if
SEQUENCE_KMER_COUNT is in `input_features`.
additional_output: optional list of strings contains additional outputs.
Returns:
inputs: LabeledTensor with dtype=float32 and axes
[batch_axis, input_position_axis, input_channel_axis], of one-hot-encoded
rasterized sequences for input into machine learning models.
outputs: LabeledTensor with dtype=float32 and axes [batch_axis, output_axis]
denoting possible output tensors, including counts and binding array
measurements.
"""
sequence_length = experiment_proto.sequence_length
count_names = selection.all_count_names(experiment_proto)
array_names = selection.binding_array_names(experiment_proto)
sequence_tensor = feature_tensors['sequence']
batch_axis = sequence_tensor.axes['batch']
position_axis = ('position', list(range(sequence_length)))
inputs = {}
if SEQUENCE_ONE_HOT in input_features:
seq_indices = custom_ops.dna_sequence_to_indices(
sequence_tensor, sequence_length)
tensor = tf.one_hot(seq_indices, depth=4, dtype=tf.float32)
channel_axis = ('channel', list(dna.DNA_BASES))
axes = [batch_axis, position_axis, channel_axis]
one_hots = lt.LabeledTensor(tensor, axes)
inputs[SEQUENCE_ONE_HOT] = one_hots
if SEQUENCE_KMER_COUNT in input_features:
raw_counts = custom_ops.count_all_dna_kmers(sequence_tensor,
kmer_k_max)
kmer_axis = lt.Axis('kmer', _kmer_labels(kmer_k_max))
counts = lt.LabeledTensor(raw_counts, [batch_axis, kmer_axis])
means, stds = _all_kmer_mean_and_std(kmer_k_max, sequence_length)
mean_count = lt.constant(means, tf.float32, axes=[kmer_axis])
std_count = lt.constant(stds, tf.float32, axes=[kmer_axis])
inputs[SEQUENCE_KMER_COUNT] = (
(lt.cast(counts, tf.float32) - mean_count) / std_count)
if STRUCTURE_PARTITION_FUNCTION in input_features:
with tf.name_scope('structure_partition_fn'):
raw_pf_tensor = lt.expand_dims(
feature_tensors['partition_function'],
['batch', 'partition_fn_axis'])
inputs[STRUCTURE_PARTITION_FUNCTION] = lt.log(raw_pf_tensor)
output_names = count_names + array_names
outputs = [lt.cast(feature_tensors[k], tf.float32) for k in output_names]
if additional_output and additional_output[0]:
outputs += [
lt.cast(feature_tensors[k], tf.float32) for k in additional_output
]
output_names += additional_output
outputs = lt.pack(outputs, ('output', output_names), axis_position=1)
if skip_all_zero_counts:
with tf.name_scope('counts_filtering'):
counts = lt.select(outputs, {'output': count_names})
keep = lt.reduce_any(lt.not_equal(counts, 0.0), 'output')
inputs = {k: lt.boolean_mask(v, keep) for k, v in inputs.items()}
outputs = lt.boolean_mask(outputs, keep)
return inputs, outputs
def preprocess(strs,
experiment_proto,
input_features=(SEQUENCE_ONE_HOT, ),
mode=PREPROCESS_SKIP_ALL_ZERO_COUNTS,
kmer_k_max=4,
ratio_random_dna=1,
total_reads_defining_positive=0,
additional_output=None):
"""Build a small TF graph to preprocess a minibatch of tf.Example protos.
Args:
strs: LabeledTensor holding a minibatch of serialized tf.Example protos
experiment_proto: selection_pb2.Experiment describing the experiment.
input_features: optional sequence of feature constants defined in this
module.
mode: optional preprocess mode defined in this module.
kmer_k_max: optional integer giving the maximum kmer length to use if
SEQUENCE_KMER_COUNT is in `input_features`.
ratio_random_dna: optional ratio of random sequences to inject if mode ==
PREPROCESS_INJECT_RANDOM_SEQUENCES
total_reads_defining_positive: optional integer indicating the sum of all
read counts required to be seen to classify the tensor as a "positive"
example when balancing input classes.
additional_output: optional list of strings contains additional outputs.
Returns:
inputs: LabeledTensor with dtype=float32 and axes
[batch_axis, input_position_axis, input_channel_axis], of one-hot-encoded
rasterized sequences for input into machine learning models.
outputs: LabeledTensor with dtype=float32 and axes [batch_axis, output_axis]
denoting possible output tensors, including counts and binding array
measurements.
"""
with tf.name_scope('preprocess'):
features = build_features(experiment_proto)
parsed_feature_tensors = lt.parse_example(strs, features)
count_names = selection.all_count_names(experiment_proto)
if mode == PREPROCESS_SKIP_ALL_ZERO_COUNTS:
skip_all_zero_counts = True
feature_tensors = parsed_feature_tensors
elif mode == PREPROCESS_ALL_COUNTS:
skip_all_zero_counts = False
feature_tensors = parsed_feature_tensors
elif mode == PREPROCESS_INJECT_RANDOM_SEQUENCES:
skip_all_zero_counts = False
# replace zero counts with NaN in real data
for count_name in count_names:
count = parsed_feature_tensors[count_name]
parsed_feature_tensors[count_name] = lt.LabeledTensor(
tf.where(count != 0, tf.cast(count, tf.float32),
tf.fill(tf.shape(count), np.float32(np.nan))),
count.axes)
# only random sequences will have a count of zero
input_batch_size = tf.shape(strs.tensor)[list(
strs.axes.keys()).index('batch')]
n_randoms = tf.cast(
tf.cast(input_batch_size, tf.float32) * ratio_random_dna,
tf.int32)
random_feature_tensors = random_dna_features(
experiment_proto, n_randoms)
for count_name in count_names:
random_feature_tensors[count_name] = lt.cast(
random_feature_tensors[count_name], tf.float32)
feature_tensors = {
k: lt.concat(
[random_feature_tensors[k], parsed_feature_tensors[k]],
'batch')
for k in features
}
# shuffle random and non-random inputs because preprocess batches get
# split across many mini-batches for training
batch_size = tf.shape(feature_tensors['sequence'].tensor)[0]
order = tf.random_shuffle(tf.range(batch_size, dtype=tf.int32))
order.set_shape(feature_tensors['sequence'].tensor.get_shape())
feature_tensors = {
k: lt.LabeledTensor(tf.gather(v.tensor, order), v.axes)
for k, v in feature_tensors.items()
}
else:
raise ValueError('unknown mode: %r' % mode) # pylint: disable=g-doc-exception
feature_tensors = upsample_positives(
feature_tensors,
count_names,
total_reads_defining_positive=total_reads_defining_positive,
min_fraction_positive=0.1)
inputs, outputs = create_input_and_outputs(
feature_tensors,
experiment_proto,
input_features=input_features,
kmer_k_max=kmer_k_max,
skip_all_zero_counts=skip_all_zero_counts,
additional_output=additional_output)
return inputs, outputs
