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use anyhow::Result;
use serde::Deserialize;
use std::path::Path;
use tokenizers::Tokenizer;
#[derive(Debug, Deserialize)]
struct DollyRow {
instruction: String,
#[serde(default)]
context: String,
response: String,
}
/// A tokenized example. `mask[i] = 1.0` marks the positions that count
/// towards the loss: only the answer, never the prompt.
#[derive(Debug, Clone)]
pub struct Example {
pub ids: Vec<i64>,
pub mask: Vec<f32>,
}
fn encode(tok: &Tokenizer, text: &str) -> Result<Vec<i64>> {
Ok(tok
.encode(text, false)
.map_err(|e| anyhow::anyhow!("{e}"))?
.get_ids()
.iter()
.map(|&i| i as i64)
.collect())
}
pub fn load_dolly(
path: impl AsRef<Path>,
tok: &Tokenizer,
max_len: usize,
limit: usize,
) -> Result<Vec<Example>> {
let raw = std::fs::read_to_string(path)?;
let mut out = Vec::new();
for line in raw.lines() {
if out.len() >= limit {
break;
}
let row: DollyRow = match serde_json::from_str(line) {
Ok(r) => r,
Err(_) => continue,
};
// ChatML, the SmolLM2 chat template
let user = if row.context.trim().is_empty() {
row.instruction.clone()
} else {
format!("{}\n\n{}", row.instruction, row.context)
};
let prompt = format!("<|im_start|>user\n{user}<|im_end|>\n<|im_start|>assistant\n");
let answer = format!("{}<|im_end|>", row.response);
let p = encode(tok, &prompt)?;
let a = encode(tok, &answer)?;
if p.len() + a.len() > max_len || a.is_empty() {
continue;
}
let mut ids = p.clone();
ids.extend_from_slice(&a);
let mut mask = vec![0.0; p.len()];
mask.extend(std::iter::repeat(1.0).take(a.len()));
out.push(Example { ids, mask });
}
Ok(out)
}
/// Pads a batch to its longest example. Padding has mask 0, so it adds
/// nothing to the loss.
pub struct Batch {
pub ids: Vec<i64>,
pub mask: Vec<f32>,
pub batch: usize,
pub seq: usize,
}
pub fn collate(examples: &[Example]) -> Batch {
let seq = examples.iter().map(|e| e.ids.len()).max().unwrap_or(1);
let batch = examples.len();
let mut ids = Vec::with_capacity(batch * seq);
let mut mask = Vec::with_capacity(batch * seq);
for e in examples {
ids.extend_from_slice(&e.ids);
mask.extend_from_slice(&e.mask);
for _ in e.ids.len()..seq {
ids.push(0);
mask.push(0.0);
}
}
Batch {
ids,
mask,
batch,
seq,
}
}
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