Merge branch 'perplexity'

# Conflicts:
#	lm_eval/models/gpt2.py
#	lm_eval/models/gpt3.py
#	tests/test_misc.py
#	tests/test_models.py

lm_eval/base.py

 import abc
 import random
 import numpy as np
+import re
 
-from lm_eval.metrics import mean
+from lm_eval.metrics import mean, perplexity, weighted_mean
 
 
 class LM(abc.ABC):
@@ -27,9 +28,51 @@ class LM(abc.ABC):
         :return: list
             A list of pairs (logprob, isgreedy)
             logprob: float
-                The log probability of `contination`
+                The log probability of `continuation`
             isgreedy:
-                Whether `contination` would be generated by greedy sampling from `context`
+                Whether `continuation` would be generated by greedy sampling from `context`
+        """
+        pass
+
+    @abc.abstractmethod
+    def loglikelihood_rolling(self, requests):
+        """Compute full log-likelihood of a string, with no truncation, for perplexity computation
+        - We will use the full max context length of the model.
+        - For inputs that exceed the max context length, we divide the tokenized string into chunks of up to
+        the max context length.
+        - IMPORTANT: Each document's loglikelihood/perplexity is computed *separately*, unlike other implementaitons
+          which may simply concatenate multiple documents together.
+        - IMPORTANT: We maximize the amount of context for each prediction. Specifically, for inputs that we break into
+          multiple chunks, the last input will still a full-sized context.
+          Example:
+            Input tokens: [ 0 1 2 3 4 5 6 7 8 9 ]
+            Prefix: EOT
+            Max context length: 4
+            Resulting input/prediction pairs:
+
+                INPUT:  EOT   0   1   2
+                PRED:     0   1   2   3
+
+                INPUT:    3   4   5   6
+                PRED:     4   5   6   7
+
+                INPUT:    5   6   7   8
+                PRED:             8   9
+
+          Observe that:
+            1. Each token is predicted exactly once
+            2. For the last pair, we provide the full context, but only score the last two tokens
+
+        :param requests: list
+            A list of strings
+            string: str
+                String for which we are computing per-toke  loglikelihood
+        :return: list
+            A list of pairs (logprob, isgreedy)
+            logprob: float
+                The log probability of `continuation`
+            isgreedy:
+                Whether `continuation` would be generated by greedy sampling from `context`
         """
         pass
 
@@ -247,9 +290,68 @@ class MultipleChoiceTask(Task):
         }
 
 
+class PerplexityTask(Task, abc.ABC):
+
+    def has_training_docs(self):
+        return False
+
+    def fewshot_description(self):
+        return ""
+
+    def fewshot_examples(self, k, rnd):
+        assert k == 0
+        return []
+
+    def fewshot_context(self, doc, num_fewshot, provide_description, rnd):
+        assert num_fewshot == 0
+        assert not provide_description
+        return ""
+
+    def higher_is_better(self):
+        return {
+            "word_perplexity": False,
+            "byte_perplexity": False,
+            "bits_per_byte": False,
+        }
+
+    def doc_to_text(self, doc):
+        return doc
+
+    def doc_to_target(self, doc):
+        raise NotImplementedError()
+
+    def construct_requests(self, doc, ctx):
+        assert not ctx
+        req = rf.loglikelihood_rolling(doc)
+        return req
+
+    def process_results(self, doc, results):
+        loglikelihood, = results
+        return {
+            "word_perplexity": loglikelihood / self.count_words(self.doc_to_text(doc)),
+            "byte_perplexity": loglikelihood / self.count_bytes(self.doc_to_text(doc)),
+            "bits_per_byte": (-loglikelihood, self.count_bytes(self.doc_to_text(doc)))
+        }
+
+    def aggregation(self):
+        return {
+            "word_perplexity": perplexity,
+            "byte_perplexity": perplexity,
+            "bits_per_byte": weighted_mean
+        }
+
+    def count_bytes(self, s):
+        return len(s.encode("utf-8"))
+    
+    def count_words(self, s):
+        """ Downstream tasks with custom word boundaries should override this! """
+        return len(re.split(r"\s+", s))
+
+
 req_ret_lens = {
     'loglikelihood': 2,
     'greedy_until': None,
+    'loglikelihood_rolling': None,
 }
 
 import os

lm_eval/evaluator.py

@@ -64,6 +64,7 @@ def evaluate(lm, task_dict, provide_description, num_fewshot, limit):
         # only in index. We could implement some kind of caching, but that would be more of a bandaid
         # solution. we could also implement some kind of autogrouping here; they should end up next to each other.
 
+        print("Running", reqtype, "requests")
         resps = getattr(lm, reqtype)([req.args for req in reqs])
 
         resps = [x if req.index is None else x[req.index] for x, req in zip(resps, reqs)]

lm_eval/metrics.py

@@ -94,6 +94,11 @@ def perplexity(items):
     return math.exp(-mean(items))
 
 
+def weighted_mean(items):
+    a, b = zip(*items)
+    return sum(a) / sum(b)
+
+
 def bleu(items):
     """The Bilingual Evaluation Understudy Score, or BLEU for short, is a metric
     for evaluating a generated sentence to a reference sentence. It counts matching

lm_eval/models/dummy.py

@@ -26,3 +26,11 @@ class DummyLM(LM):
             assert ctx.strip() != ''
 
         return res
+
+    def loglikelihood_rolling(self, requests):
+        res = []
+        
+        for _ in requests:
+            res.append(-random.random())
+
+        return res
\ No newline at end of file

lm_eval/models/gpt2.py

@@ -5,10 +5,13 @@ import torch.nn.functional as F
 from lm_eval.base import LM
 from lm_eval import utils
 from tqdm import tqdm
+import numpy as np
 
 
 class GPT2LM(LM):
     MAX_GEN_TOKS = 256
+    VOCAB_SIZE = 50257
+    EOT_TOKEN_ID = 50256
 
     def __init__(self, device='cuda', pretrained='gpt2', batch_size=1):
         super().__init__()
@@ -51,7 +54,7 @@ class GPT2LM(LM):
         for context, continuation in requests:
             if context == "":
                 # end of text as context
-                context_enc = [50256]
+                context_enc = [self.EOT_TOKEN_ID]
             else:
                 context_enc = self.tokenizer.encode(context)
 
@@ -61,7 +64,36 @@ class GPT2LM(LM):
 
         return self._loglikelihood_tokens(new_reqs)
 
-    def _loglikelihood_tokens(self, requests):
+    def loglikelihood_rolling(self, requests):
+        # TODO: Implement caching once we've confirmed the perplexity implementation
+        # TODO: automatic batch size detection for vectorization
+
+        loglikelihoods = []
+        with torch.no_grad():
+            for string, in tqdm(requests):
+                encoded = self.tokenizer.encode_plus(string)["input_ids"]
+
+                rolling_token_windows = list(map(utils.make_disjoint_window, utils.get_rolling_token_windows(
+                    token_list=encoded,
+                    prefix_token=self.EOT_TOKEN_ID,
+                    max_seq_len=self.max_length,
+                    context_len=1,
+                )))
+
+                rolling_token_windows = [(None,) + x for x in rolling_token_windows]
+
+                # TODO: extract out this call so it only gets called once and also somehow figure out partial caching for that
+                string_nll = self._loglikelihood_tokens(rolling_token_windows, disable_tqdm=True)
+                
+                # discard is_greedy
+                string_nll = [x[0] for x in string_nll]
+                
+                string_nll = sum(string_nll)
+                loglikelihoods.append(string_nll)
+
+        return loglikelihoods
+
+    def _loglikelihood_tokens(self, requests, disable_tqdm=False):
         # TODO: implement some kind of efficient-request-middleware that lumps together requests with the same context
         res = []
         with torch.no_grad():
@@ -78,18 +110,38 @@ class GPT2LM(LM):
             
             # TODO: automatic (variable) batch size detection for vectorization
             reord = utils.Reorderer(requests, _collate)
-            for chunk in utils.chunks(tqdm(reord.get_reordered()), self.batch_size):
+            for chunk in utils.chunks(tqdm(reord.get_reordered(), disable=disable_tqdm), self.batch_size):
                 inps = []
+                contlens = []
                 inplens = []
-                ctxlens = []
 
                 padding_length = None
+
+                # because vectorizing is annoying, we first convert each (context, continuation) pair to padded
+                # tensors, then we pack them together into a batch, call the model, and then pick it all apart
+                # again because vectorizing is annoying
+
                 for _, context_enc, continuation_enc in chunk:
+                    # sanity check
+                    assert len(context_enc) > 0
+                    assert len(continuation_enc) > 0
+                    assert len(continuation_enc) <= self.max_length
+
+                    # how this all works:
+                    #          CTX      CONT
+                    # inp    0 1 2 3|4 5 6 7 8 9 <- last token is deleted by inp[:, :-1]
+                    # gpt2    \               \
+                    # logits   1 2 3|4 5 6 7 8 9   <- the ctx half gets tossed out by the [:, -len(continuation_enc):, :self.VOCAB_SIZE] slice
+                    # cont_toks      4 5 6 7 8 9
+
                     # when too long to fit in context, truncate from the left
-                    inp = torch.tensor((context_enc + continuation_enc)[-self.max_length:], dtype=torch.long).to(self.device)
-                    ctxlen = len(context_enc) - max(0, len(context_enc) + len(continuation_enc) - self.max_length)
+                    inp = torch.tensor(
+                        (context_enc + continuation_enc)[-(self.max_length+1):][:-1]
+                    , dtype=torch.long).to(self.device)
                     inplen, = inp.shape
 
+                    cont = continuation_enc
+
                     # since in _collate we make sure length is descending, the longest is always the first one.
                     padding_length = padding_length if padding_length is not None else inplen
 
@@ -100,19 +152,24 @@ class GPT2LM(LM):
                     ], dim=0)
 
                     inps.append(inp.unsqueeze(0))
+                    contlens.append(cont)
                     inplens.append(inplen)
-                    ctxlens.append(ctxlen)
 
-                multi_logits = F.log_softmax(self.gpt2(torch.cat(inps, dim=0))[0][:, :, :50257], dim=-1)  # [batch, seq, vocab]
+                multi_logits = F.log_softmax(self.gpt2(torch.cat(inps, dim=0))[0][:, :, :50257], dim=-1).cpu()  # [batch, seq, vocab]
+
+                for (cache_key, _, _), logits, inp, inplen, cont_toks in zip(chunk, multi_logits, inps, inplens, contlens):
+                    contlen = len(cont_toks)
 
-                for (cache_key, _, _), logits, ctxlen, inp, inplen in zip(chunk, multi_logits, ctxlens, inps, inplens):
-                    logits = logits[ctxlen - 1:inplen - 1].unsqueeze(0) # [1, seq, vocab]
+                    logits = logits[inplen-contlen:inplen].unsqueeze(0) # [1, seq, vocab]
 
                     greedy_tokens = logits.argmax(dim=-1)
-                    cont_toks = inp[:, ctxlen:inplen]  # [1, seq]
+
+                    # cont_toks :: [1, seq]
+                    cont_toks = torch.tensor(cont_toks, dtype=torch.long).unsqueeze(0)
+
                     max_equal = (greedy_tokens == cont_toks).all()
 
-                    last_token_slice = logits[:, -1, :].squeeze(0).tolist()
+                    #last_token_slice = logits[:, -1, :].squeeze(0).tolist()
 
                     logits = torch.gather(logits, 2, cont_toks.unsqueeze(-1)).squeeze(-1) # [1, seq]
 

lm_eval/models/gpt3.py

 import os
+import numpy as np
 import transformers
 from lm_eval.base import LM
 from lm_eval import utils
@@ -58,6 +59,7 @@ class GPT3LM(LM):
         self.tokenizer.pad_token = "<|endoftext|>"
         assert self.tokenizer.encode('hello\n\nhello') == [31373, 198, 198, 31373]
         self.truncate = truncate
+        self.end_of_text_token_id = self.tokenizer.convert_tokens_to_ids(["<|endoftext|>"])[0]
 
         # Read from environment variable OPENAI_API_SECRET_KEY
         openai.api_key = os.environ["OPENAI_API_SECRET_KEY"]
@@ -83,6 +85,30 @@ class GPT3LM(LM):
 
         return self._loglikelihood_tokens(new_reqs)
 
+    def loglikelihood_rolling(self, requests):
+        # TODO: switch implementation to use _loglikelihood_tokens rather than having it do its own thing
+
+        loglikelihoods = []
+        for string, in tqdm(requests):
+            encoded = self.tokenizer.encode_plus(string)["input_ids"]
+            rolling_token_windows = utils.get_rolling_token_windows(
+                token_list=encoded,
+                prefix_token=self.end_of_text_token_id,
+                max_seq_len=self.MAX_LENGTH,
+                context_len=1,
+            )
+            string_loglikelihoods = []
+            for input_tokens, pred_tokens in rolling_token_windows:
+                block_output = self.get_token_logprobs(
+                    input_tokens=input_tokens,
+                    pred_tokens=pred_tokens,
+                )
+                string_loglikelihoods.append(block_output["logprobs"])
+            string_loglikelihoods = np.concatenate(string_loglikelihoods).sum()
+            loglikelihoods.append(string_loglikelihoods)
+
+        return loglikelihoods
+
     def _loglikelihood_tokens(self, requests):
         import openai
         res = []
@@ -95,7 +121,7 @@ class GPT3LM(LM):
             return (-len(toks), tuple(toks))
         
         reord = utils.Reorderer(requests, _collate)
-        
+
         for chunk in tqdm(list(utils.chunks(reord.get_reordered(), self.REQ_CHUNK_SIZE))):
             inps = []
             ctxlens = []
@@ -122,9 +148,30 @@ class GPT3LM(LM):
                 # partial caching
                 if cache_key is not None:
                     self.cache_hook.add_partial("loglikelihood", cache_key, answer)
-            
+
         return reord.get_original(res)
 
+    def get_token_logprobs(self, input_tokens, pred_tokens):
+        pred_start = len(input_tokens) - len(pred_tokens) + 1
+        # We're going to stitch together the input_tokens and pred_tokens
+        # In the longest case, this gets us to length = max_seq_len+1 (which the API works with)
+        assert input_tokens[pred_start:] == pred_tokens[:-1]
+        token_ids = input_tokens + [pred_tokens[-1]]
+        response = oa_completion(
+            engine=self.engine,
+            prompt=token_ids,
+            max_tokens=0,
+            temperature=0.0,
+            logprobs=0,
+            echo=True,
+        )
+        logprobs = np.array(response["choices"][0]["logprobs"]["token_logprobs"][pred_start:])
+        positions = np.arange(pred_start-1, pred_start-1 + len(token_ids[pred_start:]))
+        return {
+            "logprobs": logprobs,
+            "positions": positions,
+        }
+
     def greedy_until(self, requests):
         if not requests: return []
         import openai

lm_eval/tasks/__init__.py

@@ -37,6 +37,7 @@ from . import hendrycks_test
 from . import hendrycks_math
 from . import cbt
 from . import lambada_cloze
+from . import pile
 
 ########################################
 # Translation tasks
@@ -171,6 +172,31 @@ TASK_REGISTRY = {
     "cycle_letters": unscramble.CycleLetters,
     "random_insertion": unscramble.RandomInsertion,
     "reversed_words": unscramble.ReversedWords,
+
+    # Pile
+    "pile_arxiv": pile.PileArxiv,
+    "pile_books3": pile.PileBooks3,
+    "pile_bookcorpus2": pile.PileBookCorpus2,
+    "pile_commoncrawl": pile.PileCommonCrawl,
+    "pile_dm-mathematics": pile.PileDmMathematics,
+    "pile_enron": pile.PileEnron,
+    "pile_europarl": pile.PileEuroparl,
+    "pile_freelaw": pile.PileFreeLaw,
+    "pile_github": pile.PileGithub,
+    "pile_gutenberg": pile.PileGutenberg,
+    "pile_hackernews": pile.PileHackernews,
+    "pile_nih-exporter": pile.PileNIHExporter,
+    "pile_opensubtitles": pile.PileOpenSubtitles,
+    "pile_openwebtext2": pile.PileOpenWebText2,
+    "pile_philpapers": pile.PilePhilPapers,
+    "pile_pile-cc": pile.PilePileCc,
+    "pile_pubmed-abstracts": pile.PilePubmedAbstracts,
+    "pile_pubmed-central": pile.PilePubmedCentral,
+    "pile_stackexchange": pile.PileStackExchange,
+    "pile_uspto": pile.PileUspto,
+    "pile_ubuntu-irc": pile.PileUbuntuIrc,
+    "pile_wikipedia": pile.PileWikipedia,
+    "pile_youtubesubtitles": pile.PileYoutubeSubtitles,
 }
 
 

lm_eval/tasks/pile.py

+import os
+
+import lm_dataformat
+import abc
+import numpy as np
+from lm_eval.base import rf, PerplexityTask
+from ..metrics import mean, matthews_corrcoef, f1_score
+from ..utils import general_detokenize
+from best_download import download_file
+
+
+class PilePerplexityTask(PerplexityTask, abc.ABC):
+
+    PILE_SET_NAME = None
+    VAL_PATH = 'data/pile/val.jsonl.zst'
+    TEST_PATH = 'data/pile/test.jsonl.zst'
+
+    def download(self):
+        # TODO: separate pile val/test out by component so we don't have to scan the entire file once per set
+        os.makedirs("data/pile/", exist_ok=True)
+        if not os.path.exists(self.VAL_PATH):
+            download_file("https://the-eye.eu/public/AI/pile/val.jsonl.zst", self.VAL_PATH)
+        if not os.path.exists(self.TEST_PATH):
+            download_file("https://the-eye.eu/public/AI/pile/test.jsonl.zst", self.TEST_PATH)
+
+    def validation_docs(self):
+        rdr = lm_dataformat.Reader(self.VAL_PATH)
+        for doc, metadata in rdr.stream_data(get_meta=True):
+            if metadata["pile_set_name"] == self.PILE_SET_NAME:
+                yield doc
+
+    def test_docs(self):
+        rdr = lm_dataformat.Reader(self.TEST_PATH)
+        for doc, metadata in rdr.stream_data(get_meta=True):
+            if metadata["pile_set_name"] == self.PILE_SET_NAME:
+                yield doc
+
+    def has_validation_docs(self):
+        return True
+
+    def has_test_docs(self):
+        return True
+
+
+class PileArxiv(PilePerplexityTask):
+    PILE_SET_NAME = "ArXiv"
+
+
+class PileBooks3(PilePerplexityTask):
+    PILE_SET_NAME = "Books3"
+
+
+class PileBookCorpus2(PilePerplexityTask):
+    PILE_SET_NAME = "BookCorpus2"
+
+
+class PileCommonCrawl(PilePerplexityTask):
+    PILE_SET_NAME = "CommonCrawl"
+
+
+class PileDmMathematics(PilePerplexityTask):
+    PILE_SET_NAME = "DM Mathematics"
+
+
+class PileEnron(PilePerplexityTask):
+    PILE_SET_NAME = "Enron Emails"
+
+
+class PileEuroparl(PilePerplexityTask):
+    PILE_SET_NAME = "EuroParl"
+
+
+class PileFreeLaw(PilePerplexityTask):
+    PILE_SET_NAME = "FreeLaw"
+
+
+class PileGithub(PilePerplexityTask):
+    PILE_SET_NAME = "Github"
+
+
+class PileGutenberg(PilePerplexityTask):
+    PILE_SET_NAME = "Gutenberg (PG-19)"
+
+
+class PileHackernews(PilePerplexityTask):
+    PILE_SET_NAME = "HackerNews"
+
+
+class PileNIHExporter(PilePerplexityTask):
+    PILE_SET_NAME = "NIH ExPorter"
+
+
+class PileOpenSubtitles(PilePerplexityTask):
+    PILE_SET_NAME = "OpenSubtitles"
+
+
+class PileOpenWebText2(PilePerplexityTask):
+    PILE_SET_NAME = "OpenWebText2"
+
+
+class PilePhilPapers(PilePerplexityTask):
+    PILE_SET_NAME = "PhilPapers"
+
+
+class PilePileCc(PilePerplexityTask):
+    PILE_SET_NAME = "Pile-CC"
+
+
+class PilePubmedAbstracts(PilePerplexityTask):
+    PILE_SET_NAME = "PubMed Abstracts"
+
+
+class PilePubmedCentral(PilePerplexityTask):
+    PILE_SET_NAME = "PubMed Central"
+
+
+class PileStackExchange(PilePerplexityTask):
+    PILE_SET_NAME = "StackExchange"
+
+
+class PileUspto(PilePerplexityTask):
+    PILE_SET_NAME = "USPTO Backgrounds"
+
+
+class PileUbuntuIrc(PilePerplexityTask):
+    PILE_SET_NAME = "Ubuntu IRC"
+
+
+class PileWikipedia(PilePerplexityTask):
+    PILE_SET_NAME = "Wikipedia (en)"
+
+
+class PileYoutubeSubtitles(PilePerplexityTask):
+    PILE_SET_NAME = "YoutubeSubtitles"

lm_eval/utils.py

@@ -61,6 +61,56 @@ def general_detokenize(string):
     return string
 
 
+def get_rolling_token_windows(token_list, prefix_token, max_seq_len, context_len):
+    """
+    - context_len allows for a rolling window context, allowing each prediction window to potentially
+      condition on some context
+
+    :param token_list: list
+        List of tokens to be PREDICTED
+    :param max_seq_len: int
+        max_seq_len of model (or max_seq_len we want to use)
+    :param context_len: int
+        Amount of desired token context for prediction. Needs to be at least 1.
+    :param prefix_token: token
+        Dummy token like <eos> so the first token has something to condition on
+    :return: generator
+        Generator of tuples
+            (input_tokens, pred_tokens)
+        Note: Score only the last len(pred_tokens) logits of the LM
+    """
+    assert 1 <= context_len <= max_seq_len
+    if not token_list:
+        return
+    # +1 offset, going from input->preds
+    pred_len = max_seq_len - context_len + 1
+    predicted = 0
+
+    # Special handling for first window: predict all tokens
+    first_seq_len = min(max_seq_len, len(token_list))
+    yield (
+        [prefix_token] + token_list[:first_seq_len - 1],
+        token_list[:first_seq_len]
+    )
+    predicted += first_seq_len
+
+    while predicted < len(token_list):
+        window_pred_len = min(len(token_list) - predicted, pred_len)
+        window_end = predicted + window_pred_len
+
+        yield (
+            token_list[window_end - max_seq_len - 1:window_end - 1],
+            token_list[window_end - window_pred_len:window_end],
+        )
+        predicted += window_pred_len
+
+def make_disjoint_window(pair):
+    """ Takes output from get_rolling_token_windows and makes the context not overlap with the continuation """
+
+    a, b = pair
+
+    return a[:-(len(b) - 1)], b
+
 class Reorderer:
     def __init__(self, arr, fn):
         self.size = len(arr)

tests/test_evaluator.py

@@ -15,6 +15,7 @@ def test_evaluator(taskname, Task):
 
     def ll_fn(reqs):
         for ctx, cont in reqs:
+            if len(ctx) == 0: continue
             # space convention
             assert ctx[-1] != ' '
             assert cont[0] == ' ' or ctx[-1] == '\n'
@@ -26,7 +27,18 @@ def test_evaluator(taskname, Task):
             res.append((-random.random(), False))
 
         return res
-        
+
+    def ll_perp_fn(reqs):
+        for string, in reqs:
+            assert isinstance(string, str)
+
+        res = []
+        random.seed(42)
+        for _ in reqs:
+            res.append(-random.random())
+
+        return res
 
     lm.loglikelihood = ll_fn
+    lm.loglikelihood_rolling = ll_perp_fn
     evaluator.evaluate(lm, task_dict, False, 0, 10)

tests/test_misc.py

@@ -7,6 +7,6 @@ def test_bootstrapping():
     random.seed(42)
     arr = [random.random() for _ in range(1000)]
     expected = metrics.mean_stderr(arr)
-    bootstrapped = metrics.bootstrap_stderr(metrics.mean, arr)
+    bootstrapped = metrics.bootstrap_stderr(metrics.mean, arr, iters=100000)
 
     assert bootstrapped == pytest.approx(expected, abs=1e-4)

tests/test_models.py

@@ -41,4 +41,19 @@ def test_gpt2():
     targets = [-61.60536193847656, -56.57843780517578, -62.131004333496094, -9.799489974975586, -153.96334838867188, -341.222900390625, -731.1475830078125, -61.60536193847656, -8.682319641113281]
 
     for (pred, _), tgt in zip(vals, targets):
-        assert pred == pytest.approx(tgt, abs=1e-3)
+        assert pred == pytest.approx(tgt, abs=1e-3)
\ No newline at end of file
+
+
+
+def test_gpt2_perplexity():
+    gpt2 = models.get_model('gpt2').create_from_arg_string("device=cpu")
+    test_string = "We study empirical scaling laws for language model performance on the cross-entropy loss."
+    perplexity = gpt2.loglikelihood_perplexity([(test_string,)])[0]
+    tgt = sum([-4.9599953, -8.069298, -8.308624, -10.178513, -8.906924, -1.9318912, -7.745445, -7.146077, -5.2072, -3.5882986, -1.9957212, -8.044922, -0.20841774, -5.1096807, -0.099879116, -8.888423, -4.6180487])
+    assert perplexity == pytest.approx(tgt, abs=1e-3)
+
+    # Hack: modify gpt2 to have shorter context length to induce rolling windows
+    gpt2.max_length = 5
+    perplexity = gpt2.loglikelihood_perplexity([(test_string,)])[0]
+    tgt = sum([-4.96001, -8.069275, -8.308612, -10.178482, -8.90691, -4.037338, -8.09261, -11.662385, -10.206891, -4.425003, -2.2563353, -7.909143, -1.9304147, -7.3610134, -2.3120654, -7.3229, -2.1643813])
+    assert perplexity == pytest.approx(tgt, abs=1e-3)

tests/test_utils.py

+from lm_eval.utils import get_rolling_token_windows, make_disjoint_window
+
+
+# noinspection DuplicatedCode
+def test_get_rolling_token_windows_v1():
+    gold = [
+        ([-100, 0, 1, 2, 3, 4, 5, 6, 7, 8], [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]),
+        ([9, 10, 11, 12, 13, 14, 15, 16, 17, 18], [10, 11, 12, 13, 14, 15, 16, 17, 18, 19]),
+        ([19, 20, 21, 22, 23, 24, 25, 26, 27, 28], [20, 21, 22, 23, 24, 25, 26, 27, 28, 29]),
+        ([23, 24, 25, 26, 27, 28, 29, 30, 31, 32], [30, 31, 32, 33]),
+    ]
+    x = list(range(34))
+    generator = get_rolling_token_windows(
+        token_list=x,
+        prefix_token=-100,
+        max_seq_len=10,
+        context_len=1,
+    )
+    pred_length = 0
+    output = []
+    for input_tokens, pred_tokens in generator:
+        output.append((input_tokens, pred_tokens))
+        pred_length += len(pred_tokens)
+    assert pred_length == len(x)
+    assert gold == output
+
+
+# noinspection DuplicatedCode
+def test_get_rolling_token_windows_v2():
+    gold = [
+        ([-100, 0, 1, 2, 3, 4, 5, 6, 7, 8], [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]),
+        ([2, 3, 4, 5, 6, 7, 8, 9, 10, 11], [10, 11, 12]),
+        ([5, 6, 7, 8, 9, 10, 11, 12, 13, 14], [13, 14, 15]),
+        ([8, 9, 10, 11, 12, 13, 14, 15, 16, 17], [16, 17, 18]),
+        ([11, 12, 13, 14, 15, 16, 17, 18, 19, 20], [19, 20, 21]),
+        ([14, 15, 16, 17, 18, 19, 20, 21, 22, 23], [22, 23, 24]),
+        ([17, 18, 19, 20, 21, 22, 23, 24, 25, 26], [25, 26, 27]),
+        ([20, 21, 22, 23, 24, 25, 26, 27, 28, 29], [28, 29, 30]),
+        ([23, 24, 25, 26, 27, 28, 29, 30, 31, 32], [31, 32, 33]),
+    ]
+    x = list(range(34))
+    generator = get_rolling_token_windows(
+        token_list=x,
+        prefix_token=-100,
+        max_seq_len=10,
+        context_len=8,
+    )
+    pred_length = 0
+    output = []
+    for input_tokens, pred_tokens in generator:
+        output.append((input_tokens, pred_tokens))
+        pred_length += len(pred_tokens)
+    assert pred_length == len(x)
+    assert gold == output
+
+
+# noinspection DuplicatedCode
+def test_get_rolling_token_windows_v3():
+    gold = [
+        ([-100, 0, 1, 2, 3, 4, 5, 6, 7, 8], [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]),
+        ([0, 1, 2, 3, 4, 5, 6, 7, 8, 9], [10]),
+        ([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], [11]),
+        ([2, 3, 4, 5, 6, 7, 8, 9, 10, 11], [12]),
+        ([3, 4, 5, 6, 7, 8, 9, 10, 11, 12], [13]),
+        ([4, 5, 6, 7, 8, 9, 10, 11, 12, 13], [14]),
+        ([5, 6, 7, 8, 9, 10, 11, 12, 13, 14], [15]),
+        ([6, 7, 8, 9, 10, 11, 12, 13, 14, 15], [16]),
+        ([7, 8, 9, 10, 11, 12, 13, 14, 15, 16], [17]),
+        ([8, 9, 10, 11, 12, 13, 14, 15, 16, 17], [18]),
+        ([9, 10, 11, 12, 13, 14, 15, 16, 17, 18], [19]),
+        ([10, 11, 12, 13, 14, 15, 16, 17, 18, 19], [20]),
+        ([11, 12, 13, 14, 15, 16, 17, 18, 19, 20], [21]),
+        ([12, 13, 14, 15, 16, 17, 18, 19, 20, 21], [22]),
+        ([13, 14, 15, 16, 17, 18, 19, 20, 21, 22], [23]),
+        ([14, 15, 16, 17, 18, 19, 20, 21, 22, 23], [24]),
+        ([15, 16, 17, 18, 19, 20, 21, 22, 23, 24], [25]),
+        ([16, 17, 18, 19, 20, 21, 22, 23, 24, 25], [26]),
+        ([17, 18, 19, 20, 21, 22, 23, 24, 25, 26], [27]),
+        ([18, 19, 20, 21, 22, 23, 24, 25, 26, 27], [28]),
+        ([19, 20, 21, 22, 23, 24, 25, 26, 27, 28], [29]),
+        ([20, 21, 22, 23, 24, 25, 26, 27, 28, 29], [30]),
+        ([21, 22, 23, 24, 25, 26, 27, 28, 29, 30], [31]),
+        ([22, 23, 24, 25, 26, 27, 28, 29, 30, 31], [32]),
+        ([23, 24, 25, 26, 27, 28, 29, 30, 31, 32], [33]),
+    ]
+    x = list(range(34))
+    generator = get_rolling_token_windows(
+        token_list=x,
+        prefix_token=-100,
+        max_seq_len=10,
+        context_len=10,
+    )
+    pred_length = 0
+    output = []
+    for input_tokens, pred_tokens in generator:
+        output.append((input_tokens, pred_tokens))
+        pred_length += len(pred_tokens)
+    assert pred_length == len(x)
+    assert gold == output
+
+
+# noinspection DuplicatedCode
+def test_get_rolling_token_windows_v4():
+    gold = [
+        ([-100, 0, 1, 2, 3, 4, 5, 6, 7, 8], [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]),
+        ([0, 1, 2, 3, 4, 5, 6, 7, 8, 9], [10]),
+        ([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], [11]),
+        ([2, 3, 4, 5, 6, 7, 8, 9, 10, 11], [12]),
+        ([3, 4, 5, 6, 7, 8, 9, 10, 11, 12], [13]),
+        ([4, 5, 6, 7, 8, 9, 10, 11, 12, 13], [14]),
+        ([5, 6, 7, 8, 9, 10, 11, 12, 13, 14], [15]),
+        ([6, 7, 8, 9, 10, 11, 12, 13, 14, 15], [16]),
+        ([7, 8, 9, 10, 11, 12, 13, 14, 15, 16], [17]),
+        ([8, 9, 10, 11, 12, 13, 14, 15, 16, 17], [18]),
+        ([9, 10, 11, 12, 13, 14, 15, 16, 17, 18], [19]),
+        ([10, 11, 12, 13, 14, 15, 16, 17, 18, 19], [20]),
+        ([11, 12, 13, 14, 15, 16, 17, 18, 19, 20], [21]),
+        ([12, 13, 14, 15, 16, 17, 18, 19, 20, 21], [22]),
+        ([13, 14, 15, 16, 17, 18, 19, 20, 21, 22], [23]),
+        ([14, 15, 16, 17, 18, 19, 20, 21, 22, 23], [24]),
+        ([15, 16, 17, 18, 19, 20, 21, 22, 23, 24], [25]),
+        ([16, 17, 18, 19, 20, 21, 22, 23, 24, 25], [26]),
+        ([17, 18, 19, 20, 21, 22, 23, 24, 25, 26], [27]),
+        ([18, 19, 20, 21, 22, 23, 24, 25, 26, 27], [28]),
+        ([19, 20, 21, 22, 23, 24, 25, 26, 27, 28], [29]),
+
+    ]
+    x = list(range(30))
+    generator = get_rolling_token_windows(
+        token_list=x,
+        prefix_token=-100,
+        max_seq_len=10,
+        context_len=10,
+    )
+    pred_length = 0
+    output = []
+    for input_tokens, pred_tokens in generator:
+        output.append((input_tokens, pred_tokens))
+        pred_length += len(pred_tokens)
+    assert pred_length == len(x)
+    assert gold == output
+
+
+# noinspection DuplicatedCode
+def test_get_rolling_token_windows_v5():
+    gold = [
+        ([-100, 0, 1, 2, 3, 4, 5, 6, 7, 8], [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]),
+        ([9, 10, 11, 12, 13, 14, 15, 16, 17, 18], [10, 11, 12, 13, 14, 15, 16, 17, 18, 19]),
+        ([19, 20, 21, 22, 23, 24, 25, 26, 27, 28], [20, 21, 22, 23, 24, 25, 26, 27, 28, 29]),
+    ]
+    x = list(range(30))
+    generator = get_rolling_token_windows(
+        token_list=x,
+        prefix_token=-100,
+        max_seq_len=10,
+        context_len=1,
+    )
+    pred_length = 0
+    output = []
+    for input_tokens, pred_tokens in generator:
+        output.append((input_tokens, pred_tokens))
+        pred_length += len(pred_tokens)
+    assert pred_length == len(x)
+    assert gold == output
+
+
+# noinspection DuplicatedCode
+def test_get_rolling_token_windows_v6():
+    gold = [
+        ([-100, 0], [0, 1]),
+        ([1, 2], [2, 3]),
+        ([3, 4], [4, 5]),
+        ([5, 6], [6, 7]),
+        ([6, 7], [8]),
+    ]
+    x = list(range(9))
+    generator = get_rolling_token_windows(
+        token_list=x,
+        prefix_token=-100,
+        max_seq_len=2,
+        context_len=1,
+    )
+    pred_length = 0
+    output = []
+    for input_tokens, pred_tokens in generator:
+        output.append((input_tokens, pred_tokens))
+        pred_length += len(pred_tokens)
+    assert pred_length == len(x)
+    assert gold == output
+
+
+def test_get_rolling_token_windows_empty():
+    generator = get_rolling_token_windows(
+        token_list=[],
+        prefix_token=-100,
+        max_seq_len=2,
+        context_len=1,
+    )
+    n = 0
+    for _ in generator:
+        n += 1
+    assert n == 0
+
+
+def test_make_disjoint_window():
+    assert make_disjoint_window(([1,2,3,4,5], [2,3,4,5,6])) == ([1], [2,3,4,5,6])
+    assert make_disjoint_window(([1,2,3,4,5], [4,5,6])) == ([1,2,3], [4,5,6])
\ No newline at end of file