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import random
import numpy as np
import torch
import torch.nn as nn
from torch.nn import functional as F
def set_seed(seed):
random.seed(seed)
np.random.seed(seed)
torch.manual_seed(seed)
torch.cuda.manual_seed_all(seed)
def top_k_logits(logits, k):
v, ix = torch.topk(logits, k)
out = logits.clone()
out[out < v[:, [-1]]] = -float('Inf')
return out
@torch.no_grad()
def sample(model, x, steps, temperature=1.0, sample=False, top_k=None):
"""
take a conditioning sequence of indices in x (of shape (b,t)) and predict the next token in
the sequence, feeding the predictions back into the model each time. Clearly the sampling
has quadratic complexity unlike an RNN that is only linear, and has a finite context window
of block_size, unlike an RNN that has an infinite context window.
"""
block_size = model.get_block_size()
model.eval()
for k in range(steps):
x_cond = x if x.size(1) <= block_size else x[:, -block_size:] # crop context if needed
logits, _ = model(x_cond)
# pluck the logits at the final step and scale by temperature
logits = logits[:, -1, :] / temperature
# optionally crop probabilities to only the top k options
if top_k is not None:
logits = top_k_logits(logits, top_k)
# apply softmax to convert to probabilities
probs = F.softmax(logits, dim=-1)
# sample from the distribution or take the most likely
if sample:
ix = torch.multinomial(probs, num_samples=1)
else:
_, ix = torch.topk(probs, k=1, dim=-1)
# append to the sequence and continue
x = torch.cat((x, ix), dim=1)
return x
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