Source code for alibi_detect.utils.tensorflow.prediction

from functools import partial
from typing import Callable, Type, Union

import numpy as np
import tensorflow as tf
from alibi_detect.utils.prediction import tokenize_transformer


def predict_batch(x: Union[list, np.ndarray, tf.Tensor], model: Union[Callable, tf.keras.Model],
                  batch_size: int = int(1e10), preprocess_fn: Callable = None,
                  dtype: Union[Type[np.generic], tf.DType] = np.float32) -> Union[np.ndarray, tf.Tensor, tuple]:
    """
    Make batch predictions on a model.

    Parameters
    ----------
    x
        Batch of instances.
    model
        tf.keras model or one of the other permitted types defined in Data.
    batch_size
        Batch size used during prediction.
    preprocess_fn
        Optional preprocessing function for each batch.
    dtype
        Model output type, e.g. np.float32 or tf.float32.

    Returns
    -------
    Numpy array, tensorflow tensor or tuples of those with model outputs.
    """
    n = len(x)
    n_minibatch = int(np.ceil(n / batch_size))
    return_np = not isinstance(dtype, tf.DType)
    return_list = False
    preds: Union[list, tuple] = []
    for i in range(n_minibatch):
        istart, istop = i * batch_size, min((i + 1) * batch_size, n)
        x_batch = x[istart:istop]
        if isinstance(preprocess_fn, Callable):  # type: ignore
            x_batch = preprocess_fn(x_batch)
        preds_tmp = model(x_batch)
        if isinstance(preds_tmp, (list, tuple)):
            if len(preds) == 0:  # init tuple with lists to store predictions
                preds = tuple([] for _ in range(len(preds_tmp)))
                return_list = isinstance(preds_tmp, list)
            for j, p in enumerate(preds_tmp):
                preds[j].append(p if not return_np or isinstance(p, np.ndarray) else p.numpy())
        elif isinstance(preds_tmp, (np.ndarray, tf.Tensor)):
            preds.append(preds_tmp if not return_np or isinstance(preds_tmp, np.ndarray)  # type: ignore
                         else preds_tmp.numpy())
        else:
            raise TypeError(f'Model output type {type(preds_tmp)} not supported. The model output '
                            f'type needs to be one of list, tuple, np.ndarray or tf.Tensor.')
    concat = np.concatenate if return_np else tf.concat
    out = tuple(concat(p, axis=0) for p in preds) if isinstance(preds, tuple) else concat(preds, axis=0)
    if return_list:
        out = list(out)
    return out


def predict_batch_transformer(x: Union[list, np.ndarray], model: tf.keras.Model, tokenizer: Callable,
                              max_len: int, batch_size: int = int(1e10),
                              dtype: Union[Type[np.generic], tf.DType] = np.float32) \
        -> Union[np.ndarray, tf.Tensor]:
    """
    Make batch predictions using a transformers tokenizer and model.

    Parameters
    ----------
    x
        Batch of instances.
    model
        Transformer model.
    tokenizer
        Tokenizer for model.
    max_len
        Max token length.
    batch_size
        Batch size.
    dtype
        Model output type, e.g. np.float32 or tf.float32.

    Returns
    -------
    Numpy array or tensorflow tensor with model outputs.
    """
    preprocess_fn = partial(tokenize_transformer, tokenizer=tokenizer, max_len=max_len, backend='tf')
    return predict_batch(x, model, preprocess_fn=preprocess_fn, batch_size=batch_size, dtype=dtype)