ModernBERT model (#2713)

* layer_norm_no_bias

* Modernbert model.

* Format + cleanup error.

---------

Co-authored-by: laurent <laurent.mazare@gmail.com>

candle-examples/examples/modernbert/README.md

@@ -0,0 +1,12 @@
+# candle-modernbert
+
+ModernBERT is a bidirectional encoder-only language model. In this example it is used for the fill-mask task:
+
+## Usage
+
+```bash
+cargo run --example modernbert --release  -- --model modern-bert-large --prompt 'The capital of France is [MASK].'
+```
+```markdown
+Sentence: 1 : The capital of France is Paris.
+```

candle-examples/examples/modernbert/main.rs

@@ -0,0 +1,180 @@
+use std::path::PathBuf;
+
+use anyhow::{Error as E, Result};
+use candle::{Device, Tensor};
+use candle_nn::VarBuilder;
+use candle_transformers::models::modernbert;
+use clap::{Parser, ValueEnum};
+use hf_hub::{api::sync::Api, Repo, RepoType};
+use tokenizers::{PaddingParams, Tokenizer};
+
+#[derive(Debug, Clone, ValueEnum)]
+enum Model {
+    ModernBertBase,
+    ModernBertLarge,
+}
+
+#[derive(Parser, Debug)]
+#[command(author, version, about, long_about = None)]
+struct Args {
+    /// Run on CPU rather than on GPU.
+    #[arg(long)]
+    cpu: bool,
+
+    /// Enable tracing (generates a trace-timestamp.json file).
+    #[arg(long)]
+    tracing: bool,
+
+    #[arg(long)]
+    model_id: Option<String>,
+
+    #[arg(long, default_value = "main")]
+    revision: String,
+
+    #[arg(long, default_value = "modern-bert-base")]
+    model: Model,
+
+    // Path to the tokenizer file.
+    #[arg(long)]
+    tokenizer_file: Option<String>,
+
+    // Path to the weight files.
+    #[arg(long)]
+    weight_files: Option<String>,
+
+    // Path to the config file.
+    #[arg(long)]
+    config_file: Option<String>,
+
+    /// When set, compute embeddings for this prompt.
+    #[arg(long)]
+    prompt: Option<String>,
+}
+
+fn main() -> Result<()> {
+    let args = Args::parse();
+    let api = Api::new()?;
+    let model_id = match &args.model_id {
+        Some(model_id) => model_id.to_string(),
+        None => match args.model {
+            Model::ModernBertBase => "answerdotai/ModernBERT-base".to_string(),
+            Model::ModernBertLarge => "answerdotai/ModernBERT-large".to_string(),
+        },
+    };
+    let repo = api.repo(Repo::with_revision(
+        model_id,
+        RepoType::Model,
+        args.revision,
+    ));
+
+    let tokenizer_filename = match args.tokenizer_file {
+        Some(file) => std::path::PathBuf::from(file),
+        None => repo.get("tokenizer.json")?,
+    };
+
+    let config_filename = match args.config_file {
+        Some(file) => std::path::PathBuf::from(file),
+        None => repo.get("config.json")?,
+    };
+
+    let weights_filename = match args.weight_files {
+        Some(files) => PathBuf::from(files),
+        None => match repo.get("model.safetensors") {
+            Ok(safetensors) => safetensors,
+            Err(_) => match repo.get("pytorch_model.bin") {
+                Ok(pytorch_model) => pytorch_model,
+                Err(e) => {
+                    anyhow::bail!("Model weights not found. The weights should either be a `model.safetensors` or `pytorch_model.bin` file.  Error: {e}")
+                }
+            },
+        },
+    };
+
+    let config = std::fs::read_to_string(config_filename)?;
+    let config: modernbert::Config = serde_json::from_str(&config)?;
+    let mut tokenizer = Tokenizer::from_file(tokenizer_filename).map_err(E::msg)?;
+
+    let device = candle_examples::device(args.cpu)?;
+
+    let vb = if weights_filename.ends_with("model.safetensors") {
+        unsafe {
+            VarBuilder::from_mmaped_safetensors(&[weights_filename], candle::DType::F32, &device)
+                .unwrap()
+        }
+    } else {
+        println!("Loading weights from pytorch_model.bin");
+        VarBuilder::from_pth(&weights_filename, candle::DType::F32, &device).unwrap()
+    };
+    tokenizer
+        .with_padding(Some(PaddingParams {
+            strategy: tokenizers::PaddingStrategy::BatchLongest,
+            pad_id: config.pad_token_id,
+            ..Default::default()
+        }))
+        .with_truncation(None)
+        .map_err(E::msg)?;
+
+    let prompt = match &args.prompt {
+        Some(p) => vec![p.as_str()],
+        None => vec![
+            "Hello I'm a [MASK] model.",
+            "I'm a [MASK] boy.",
+            "I'm [MASK] in berlin.",
+            "The capital of France is [MASK].",
+        ],
+    };
+    let model = modernbert::ModernBertForMaskedLM::load(vb, &config)?;
+
+    let input_ids = tokenize_batch(&tokenizer, prompt.clone(), &device)?;
+    let attention_mask = get_attention_mask(&tokenizer, prompt.clone(), &device)?;
+
+    let output = model
+        .forward(&input_ids, &attention_mask)?
+        .to_dtype(candle::DType::F32)?;
+
+    let max_outs = output.argmax(2)?;
+
+    let max_out = max_outs.to_vec2::<u32>()?;
+    let max_out_refs: Vec<&[u32]> = max_out.iter().map(|v| v.as_slice()).collect();
+    let decoded = tokenizer.decode_batch(&max_out_refs, true).unwrap();
+    for (i, sentence) in decoded.iter().enumerate() {
+        println!("Sentence: {} : {}", i + 1, sentence);
+    }
+
+    Ok(())
+}
+
+pub fn tokenize_batch(
+    tokenizer: &Tokenizer,
+    input: Vec<&str>,
+    device: &Device,
+) -> anyhow::Result<Tensor> {
+    let tokens = tokenizer.encode_batch(input, true).map_err(E::msg)?;
+
+    let token_ids = tokens
+        .iter()
+        .map(|tokens| {
+            let tokens = tokens.get_ids().to_vec();
+            Tensor::new(tokens.as_slice(), device)
+        })
+        .collect::<candle::Result<Vec<_>>>()?;
+
+    Ok(Tensor::stack(&token_ids, 0)?)
+}
+
+pub fn get_attention_mask(
+    tokenizer: &Tokenizer,
+    input: Vec<&str>,
+    device: &Device,
+) -> anyhow::Result<Tensor> {
+    let tokens = tokenizer.encode_batch(input, true).map_err(E::msg)?;
+
+    let attention_mask = tokens
+        .iter()
+        .map(|tokens| {
+            let tokens = tokens.get_attention_mask().to_vec();
+            Tensor::new(tokens.as_slice(), device)
+        })
+        .collect::<candle::Result<Vec<_>>>()?;
+    Ok(Tensor::stack(&attention_mask, 0)?)
+}