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alt_generator.py
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alt_generator.py
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import cuda_ext
from model import ExLlama, ExLlamaCache
from tokenizer import ExLlamaTokenizer
from lora import ExLlamaLora
import torch
import torch.nn.functional as F
MAX_CACHED_STRINGS = 100
class ExLlamaAltGenerator:
class Settings:
temperature = 0.95
top_k = 40 # consider the most probable top_k samples, 0 to disable top_k sampling
top_p = 0.65 # consider tokens up to a cumulative probabiltiy of top_p, 0.0 to disable top_p sampling
min_p = 0.0 # Do not consider tokens with probability less than this
typical = 0.0 # Locally typical sampling threshold, 0.0 to disable typical sampling
token_repetition_penalty_max = 1.15 # Repetition penalty for most recent tokens
token_repetition_penalty_sustain = -1 # No. most recent tokens to repeat penalty for, -1 to apply to whole context
token_repetition_penalty_decay = 0 # Gradually decrease penalty over this many tokens
disallowed_tokens: list[int] = None # List of tokens to inhibit, e.g. tokenizer.eos_token_id
lora: ExLlamaLora = None # LoRA to apply when generating
# Internal state
model: ExLlama
cache: ExLlamaCache
tokenizer: ExLlamaTokenizer
tokenizer_cache = {}
settings: Settings
stop_strings: list = []
stop_tokens: list = []
held_text: str = ""
max_stop_tokens: int = 2
sequence_ids: torch.Tensor = None
sequence_str: str = None
remaining_tokens: int = 0
def __init__(self, model: ExLlama, tokenizer: ExLlamaTokenizer, cache: ExLlamaCache):
self.model = model
self.tokenizer = tokenizer
self.cache = cache
self.settings = ExLlamaAltGenerator.Settings()
def cached_tokenize(self, text: str, encode_special_characters = False):
if text in self.tokenizer_cache:
return self.tokenizer_cache[text]
while len(self.tokenizer_cache) >= MAX_CACHED_STRINGS:
del self.tokenizer_cache[next(iter(self.tokenizer_cache))] # Always removes oldest entry, as of Python 3.7
new_enc = self.tokenizer.encode(text, encode_special_characters = encode_special_characters)
self.tokenizer_cache[text] = new_enc
return new_enc
def get_num_tokens(self, text: str, encode_special_characters = False):
return self.cached_tokenize(text, encode_special_characters = encode_special_characters).shape[-1]
# Begin generating
#
# prompt: The input prompt. Will be tokenized and then truncated to the models max sequence length minus max_new_tokens
# stop_conditions: List of strings or integer token IDs that will end the sequence
# settings: ExLlamaAltGeneratorSettings
# encode_special_characters: Set to true to tokenize "</s>" etc.
def begin_stream(self, prompt: str, stop_conditions: list, max_new_tokens: int, gen_settings: Settings, encode_special_characters = False):
assert isinstance(prompt, str), "ExLlamaAltGenerator does not support batched generation"
# Tokenize prompt and limit length to allow prompt and (max) new tokens within max sequence length
max_input_tokens = self.model.config.max_seq_len - max_new_tokens
self.remaining_tokens = max_new_tokens
input_ids = self.cached_tokenize(prompt, encode_special_characters)
applied_input_ids = input_ids[:, -max_input_tokens:]
self.sequence_str = self.tokenizer.decode(applied_input_ids)[0] if applied_input_ids.shape[0] < input_ids.shape[0] else prompt
# Settings
self.stop_strings = []
self.stop_tokens = []
for t in stop_conditions:
if isinstance(t, int): self.stop_tokens += [t]
elif isinstance(t, str): self.stop_strings += [t]
else: raise ValueError("Unsupported type in stop_conditions")
self.held_text = ""
self.max_stop_tokens = 2
for ss in self.stop_strings:
self.max_stop_tokens = max(self.max_stop_tokens, self.get_num_tokens(ss) + 2)
self.settings = gen_settings
# Start generation
self.gen_begin_reuse(applied_input_ids, gen_settings)
# Get the next chunk of text in the stream
#
# Returns stream_chunk: str, EOS: bool
def stream(self):
# Check total response length
if self.remaining_tokens == 0:
self.sequence_str += self.held_text
return self.held_text, True
self.remaining_tokens -= 1
# Decode the current tail end of the sequence
old_tail = self.tokenizer.decode(self.sequence_ids[:, -self.max_stop_tokens:])[0]
# Generate a single token and append to the sequence
next_token = self.gen_single_token(self.settings)
# End immediately if it was a stop token
if next_token in self.stop_tokens:
self.sequence_str += self.held_text
return self.held_text, True
# Decode the tail end of the sequence with the added token to get (actual) characters added
new_tail = self.tokenizer.decode(self.sequence_ids[:, -(self.max_stop_tokens + 1):])[0]
self.held_text += new_tail[len(old_tail):]
# Hold text as long as it contains part of a stop string
partial_ss = False
for ss in self.stop_strings:
# Check if held_text fully contains stop string
position = self.held_text.find(ss)
if position != -1:
self.sequence_str += self.held_text[:position]
return self.held_text[:position], True
# Check for overlap between end of held_text and start of stop string
overlap = 0
for j in range(1, min(len(self.held_text), len(ss)) + 1):
if self.held_text[-j:] == ss[:j]: overlap = j
if overlap > 0: partial_ss = True
# If holding text because of a partial stop condition, return nothing but also EOS = False
if partial_ss:
return "", False
# No stop condition, so return whatever has been generated
stream_text = self.held_text
self.held_text = ""
self.sequence_str += stream_text
return stream_text, False
# Generate and return a full prompt completion. See begin_stream() above
def generate(self, prompt: str, stop_conditions: list, max_new_tokens: int, gen_settings: Settings, encode_special_characters = False):
self.begin_stream(prompt, stop_conditions, max_new_tokens, gen_settings, encode_special_characters)
response = ""
while True:
chunk, eos = self.stream()
response += chunk
if eos: break
return response
# Begin generation
def gen_begin(self, in_tokens, gen_settings):
self.sequence_ids = in_tokens.clone()
self.cache.current_seq_len = 0
self.model.forward(self.sequence_ids[:, :-1], self.cache, preprocess_only = True, lora = gen_settings.lora)
def gen_begin_reuse(self, in_tokens, gen_settings):
if self.sequence_ids is None or self.cache.current_seq_len == 0:
self.gen_begin(in_tokens, gen_settings)
return
reuse = 0
while reuse < self.sequence_ids.shape[-1] and reuse < in_tokens.shape[-1] and self.sequence_ids[0, reuse] == in_tokens[0, reuse]:
reuse += 1
if reuse < 2:
self.gen_begin(in_tokens, gen_settings)
return
self.cache.current_seq_len = reuse - 1
self.sequence_ids = in_tokens[:, :reuse]
if reuse < in_tokens.shape[-1]: self.gen_feed_tokens(in_tokens[:, reuse:], gen_settings)
def gen_feed_tokens(self, in_tokens, gen_settings):
if self.sequence_ids is None:
self.gen_begin(in_tokens, gen_settings)
return
start = self.cache.current_seq_len
self.sequence_ids = torch.cat((self.sequence_ids, in_tokens), dim = 1)
self.model.forward(self.sequence_ids[:, start : -1], self.cache, preprocess_only = True, lora = gen_settings.lora)
# Generate one token in current sequence
def gen_single_token(self, gen_settings):
# Simple sampling case:
logits = self.model.forward(self.sequence_ids[:, -1:], self.cache, lora = gen_settings.lora)
token, _ = self.sample(logits, gen_settings)
self.sequence_ids = torch.cat([self.sequence_ids, token], dim = 1)
return token
def sample(self, logits, gen_settings):
cuda_ext.ext_apply_rep_penalty_mask_cpu(self.sequence_ids,
self.settings.token_repetition_penalty_max,
self.settings.token_repetition_penalty_sustain,
self.settings.token_repetition_penalty_decay,
logits)
logits[:, :, self.tokenizer.bos_token_id] = -10000.0
if logits.dim() == 3: logits = logits[0, -1, :]
elif logits.dim() == 2: logits = logits[-1, :]
else: raise ValueError("Bad logits dimension")
# Disallow tokens
if gen_settings.disallowed_tokens is not None:
logits[gen_settings.disallowed_tokens] = float("-inf")
# Base probabilities
logits /= gen_settings.temperature
logits += 1e-8
probs = torch.softmax(logits, dim = -1)
# Top K
if gen_settings.top_k == 0:
top_probs, top_indices = torch.sort(probs, descending = True)
else:
top_probs, top_indices = torch.topk(probs, gen_settings.top_k)
top_probs = F.normalize(top_probs, p = 1, dim = -1)
# Top P
if gen_settings.top_p > 0.0:
num_top_p_probs = 0
cum_prob = top_probs[0].item()
while True:
num_top_p_probs += 1
if num_top_p_probs == top_probs.shape[-1]: break
if top_probs[num_top_p_probs].item() < gen_settings.min_p: break
cum_prob += top_probs[num_top_p_probs].item()
if cum_prob > gen_settings.top_p: break
top_probs = top_probs[:num_top_p_probs]
top_probs = F.normalize(top_probs, p = 1, dim = -1)
top_indices = top_indices[:num_top_p_probs]
# Locally typical sampling
if gen_settings.typical > 0.0:
epsilon = 1e-10
log_probs = (top_probs + epsilon).log()
neg_entropy = (top_probs * log_probs).sum()
entropy_dev = (neg_entropy - log_probs).abs()
_, entropy_dev_order = torch.sort(entropy_dev)
top_probs = top_probs.gather(-1, entropy_dev_order)
top_indices = top_indices.gather(-1, entropy_dev_order)
num_typical_probs = 0
cum_prob = top_probs[0].item()
while True:
num_typical_probs += 1
if num_typical_probs == top_probs.shape[-1]: break
cum_prob += top_probs[num_typical_probs].item()
if cum_prob > gen_settings.typical: break
top_probs = top_probs[:num_typical_probs]
top_probs = F.normalize(top_probs, p = 1, dim = -1)
top_indices = top_indices[:num_typical_probs]
# Multinomial sampling from top_probs, kept in same order as top_indices
sampled_ind = torch.multinomial(top_probs, 1)
sampled_tokens = top_indices[sampled_ind]
sampled_probs = top_probs[sampled_ind] # Return probs before second norm
# if sampled_tokens.shape[0] > 1:
# sampled_tokens, ind = sampled_tokens.sort()
# sampled_probs = sampled_probs[ind]
return sampled_tokens.unsqueeze(0), sampled_probs.unsqueeze(0)