constrained_generation.py

"""
    constrained_generation.py - use constrained beam search to generate text from a model with entered constraints
"""

import copy
import logging
logging.basicConfig(level=logging.INFO)
import time
from pathlib import Path

import yake
from transformers import AutoTokenizer, PhrasalConstraint

def get_tokenizer(model_name="gpt2", verbose=False):
    """
    get_tokenizer - returns a tokenizer object

    :param model_name: name of the model to use, default gpt2
    :param verbose: verbosity
    """
    tokenizer = AutoTokenizer.from_pretrained(
        model_name, add_special_tokens=False, padding=True, truncation=True
    )
    tokenizer.pad_token = tokenizer.eos_token
    if verbose:
        print(f"loaded tokenizer {model_name}")
    return tokenizer


def unique_words(list_of_strings):
    """
    unique_words - return a list of unique words from a list of strings. Uses set to remove duplicates.
    """
    unique_words = []
    output_list = []
    for string in list_of_strings:
        # split string into words
        words = string.split()
        # check if word is unique
        unique_status = True
        for word in words:
            if word not in unique_words:
                unique_words.append(word)
            else:
                unique_status = False
                break
        if unique_status:
            output_list.append(string)

    return output_list


def create_kw_extractor(
    language="en",
    max_ngram_size=3,
    deduplication_algo="seqm",
    windowSize=10,
    numOfKeywords=10,
    ddpt=0.7,
):
    """
    creates a keyword extractor object

    :param language: language of the text
    :param max_ngram_size: max ngram size
    :param deduplication_algo: deduplication algorithm
    :param windowSize: window size
    :param numOfKeywords: number of keywords
    :param ddpt: Deduplication Percentage Threshold

    :return: keyword extractor object
    """
    assert ddpt >= 0 and ddpt <= 1, f"need 0<thresh<1, got {ddpt}"
    return yake.KeywordExtractor(
        lan=language,
        n=max_ngram_size,
        dedupLim=ddpt,
        dedupFunc=deduplication_algo,
        windowsSize=windowSize,
        top=numOfKeywords,
        features=None,
    )


def simple_kw(body_text: str, yake_ex=None, max_kw=15, verbose=False):
    """
    simple_kw - extract keywords from a text using yake

    Args:
        body_text (str): text to extract keywords from
        yake_ex (yake.KeywordExtractor, optional): yake keyword extractor. Defaults to None.
        max_kw (int, optional): maximum number of keywords to extract. Defaults to 10.
        verbose (bool, optional): Defaults to False.

    Returns:
        list: list of keywords
    """
    yake_ex = yake_ex or create_kw_extractor(
        max_ngram_size=2,
        ddpt=0.9,
        windowSize=10,
        deduplication_algo="seqm",
        numOfKeywords=max_kw,
    )  # per optuna study

    keywords = yake_ex.extract_keywords(body_text)
    keywords_list = [str(kw[0]).lower() for kw in keywords]
    logging.info(
        f"YAKE: found {len(keywords_list)} keywords, the top {max_kw} are: {keywords_list[:max_kw]}"
    )

    if verbose:

        print(f"found {len(keywords_list)} keywords, the top {max_kw} are:")
        print(keywords_list[:max_kw])
        logging.info(f"found {len(keywords_list)} keywords, the top {max_kw} are:")

    return keywords_list[:max_kw]


def constrained_generation(
    prompt: str,
    pipeline,
    tokenizer=None,
    no_repeat_ngram_size=2,
    length_penalty=0.7,
    repetition_penalty=3.5,
    num_beams=4,
    max_generated_tokens=48,
    min_generated_tokens=2,
    timeout=300,
    num_return_sequences=1,
    verbose=False,
    full_text=False,
    force_word: str = None,
    speaker_name: str = "Person Alpha",
    responder_name: str = "Person Beta",
    **kwargs,
):
    """
    constrained_generation - generate text based on prompt and constraints

    USAGE
    -----
    response = constrained_generation("hey man - how have you been lately?",
                                        tokenizer, my_chatbot, verbose=True,
                                        force_word=" meme", num_beams=32)

    Parameters
    ----------
    prompt : str, prompt to use for generation,
    tokenizer : transformers.PreTrainedTokenizer, tokenizer to use, must be compatible with model
    pipeline : transformers.pipeline, pipeline to use, must be compatible with tokenizer & text2text model
    no_repeat_ngram_size : int, optional, default=2,
    num_beams : int, optional, default=8,
    max_generated_tokens : int, optional, default=64,
    min_generated_tokens : int, optional, default=16,
    verbose : bool, optional, default=False, print output
    force_word : _type_, optional, default=None, force word to be used in generation
    speaker_name : str, optional, default="Person Alpha", name of speaker
    responder_name : str, optional, default="Person Beta", name of responder

    Returns
    -------
    response : str, generated text
    """
    st = time.perf_counter()
    tokenizer = tokenizer or copy.deepcopy(pipeline.tokenizer)
    tokenizer.add_prefix_space = True
    tokenizer.add_special_tokens = False

    prompt_length = len(tokenizer(prompt, truncation=True).input_ids)
    if responder_name.lower() not in prompt.lower():
        prompt = f"{prompt}\n\n{responder_name}:\n"
    # key_prompt_phrases = get_keyberts(prompt)
    key_prompt_phrases = simple_kw(prompt)

    try:
        responder_name_words = responder_name.lower().split()
        speaker_name_words = speaker_name.lower().split()
    except Exception as e:
        responder_name_words = []
        speaker_name_words = []
        logging.info(f"could not split names: {e}")

    key_prompt_phrases = [
        p
        for p in key_prompt_phrases
        if not any([name in p for name in responder_name_words])
        and not any([name in p for name in speaker_name_words])
    ]
    force_flexible = unique_words(key_prompt_phrases)
    print(f"found keywords: {force_flexible}")

    if verbose:
        logging.info(f"found the following keywords: {force_flexible}")
        logging.info(
            f"forcing the word: {force_word}"
        ) if force_word is not None else logging.info("\n")
    else:
        logging.info(f"found the following keywords: {force_flexible}")

    if len(force_flexible) == 0:
        force_flexible = None
    constraints = (
        [
            PhrasalConstraint(
                tokenizer(force_word, add_special_tokens=False).input_ids,
            ),
        ]
        if force_word is not None
        else None
    )
    force_words_ids = (
        [
            tokenizer(
                force_flexible,
            ).input_ids,
        ]
        if force_flexible is not None
        else None
    )
    try:
        logging.info("generating text..")
        result = pipeline(
            prompt,
            constraints=constraints if force_word is not None else None,
            force_words_ids=force_words_ids if force_flexible is not None else None,
            max_length=None,
            max_new_tokens=max_generated_tokens,
            min_length=min_generated_tokens + prompt_length if full_text else min_generated_tokens,
            num_beams=num_beams,
            no_repeat_ngram_size=no_repeat_ngram_size,
            num_return_sequences=num_return_sequences,
            max_time=timeout,
            length_penalty=length_penalty,
            repetition_penalty=repetition_penalty,
            return_full_text=full_text,
            clean_up_tokenization_spaces=True,
            early_stopping=True,
            do_sample=False,
            **kwargs,
        )
        response = result[0]["generated_text"]
        rt = round((time.perf_counter() - st) / 60, 3)
        logging.info(f"generated response in {rt} minutes")
        if verbose:
            print(f"input prompt:\n\t{prompt}")
            print(f"response:\n\t{response}")
    except Exception as e:
        logging.info(f"could not generate response: {e}")
        response = "Sorry, I don't know how to respond to that."
    return response