Use the hub files for the marian example. (#1220)

* Use the hub files for the marian example.

* Use the secondary decoder.

* Add a readme.

* More readme.

candle-examples/examples/marian-mt/README.md

@@ -0,0 +1,19 @@
+# candle-marian-mt
+
+`marian-mt` is a neural machine translation model. In this example it is used to
+translate text from French to English. See the associated [model
+card](https://huggingface.co/Helsinki-NLP/opus-mt-tc-big-fr-en) for details on
+the model itself.
+
+## Running an example
+
+```bash
+cargo run --example marian-mt --release -- \
+    --text "Demain, dès l'aube, à l'heure où blanchit la campagne, Je partirai. Vois-tu, je sais que tu m'attends. J'irai par la forêt, j'irai par la montagne. Je ne puis demeurer loin de toi plus longtemps."
+```
+
+```
+<NIL> Tomorrow, at dawn, at the time when the country is whitening, I will go. See,
+I know you are waiting for me. I will go through the forest, I will go through the
+mountain. I cannot stay far from you any longer.</s>
+```

candle-examples/examples/marian-mt/main.rs

@@ -8,7 +8,6 @@ use anyhow::Error as E;
 use clap::Parser;
 
 use candle::{DType, Tensor};
-use candle_examples::token_output_stream::TokenOutputStream;
 use candle_nn::VarBuilder;
 use candle_transformers::models::marian;
 
@@ -18,10 +17,13 @@ use tokenizers::Tokenizer;
 #[derive(Parser)]
 struct Args {
     #[arg(long)]
-    model: String,
+    model: Option<String>,
 
     #[arg(long)]
-    tokenizer: String,
+    tokenizer: Option<String>,
+
+    #[arg(long)]
+    tokenizer_dec: Option<String>,
 
     /// Run on CPU rather than on GPU.
     #[arg(long)]
@@ -37,25 +39,52 @@ struct Args {
 }
 
 pub fn main() -> anyhow::Result<()> {
+    use hf_hub::api::sync::Api;
     let args = Args::parse();
 
     let config = marian::Config::opus_mt_tc_big_fr_en();
+    let tokenizer = {
+        let tokenizer = match args.tokenizer {
+            Some(tokenizer) => std::path::PathBuf::from(tokenizer),
+            None => Api::new()?
+                .model("lmz/candle-marian".to_string())
+                .get("tokenizer-marian-fr.json")?,
+        };
+        Tokenizer::from_file(&tokenizer).map_err(E::msg)?
+    };
+
+    let tokenizer_dec = {
+        let tokenizer = match args.tokenizer_dec {
+            Some(tokenizer) => std::path::PathBuf::from(tokenizer),
+            None => Api::new()?
+                .model("lmz/candle-marian".to_string())
+                .get("tokenizer-marian-en.json")?,
+        };
+        Tokenizer::from_file(&tokenizer).map_err(E::msg)?
+    };
 
     let device = candle_examples::device(args.cpu)?;
-    let vb = unsafe { VarBuilder::from_mmaped_safetensors(&[&args.model], DType::F32, &device)? };
+    let vb = {
+        let model = match args.model {
+            Some(model) => std::path::PathBuf::from(model),
+            None => Api::new()?
+                .model("Helsinki-NLP/opus-mt-tc-big-fr-en".to_string())
+                .get("model.safetensors")?,
+        };
+        unsafe { VarBuilder::from_mmaped_safetensors(&[&model], DType::F32, &device)? }
+    };
     let model = marian::MTModel::new(&config, vb)?;
 
-    let tokenizer = Tokenizer::from_file(&args.tokenizer).map_err(E::msg)?;
-    let mut tokenizer_dec = TokenOutputStream::new(tokenizer.clone());
     let mut logits_processor =
         candle_transformers::generation::LogitsProcessor::new(1337, None, None);
 
     let encoder_xs = {
-        let tokens = tokenizer
+        let mut tokens = tokenizer
             .encode(args.text, true)
             .map_err(E::msg)?
             .get_ids()
             .to_vec();
+        tokens.push(config.eos_token_id);
         let tokens = Tensor::new(tokens.as_slice(), &device)?.unsqueeze(0)?;
         model.encoder().forward(&tokens, 0)?
     };
@@ -70,20 +99,15 @@ pub fn main() -> anyhow::Result<()> {
         let logits = logits.squeeze(0)?;
         let logits = logits.get(logits.dim(0)? - 1)?;
         let token = logits_processor.sample(&logits)?;
+        token_ids.push(token);
         println!("{token}");
         if token == config.eos_token_id || token == config.forced_eos_token_id {
             break;
         }
-        token_ids.push(token);
-        if let Some(t) = tokenizer_dec.next_token(token)? {
-            use std::io::Write;
-            print!("{t}");
-            std::io::stdout().flush()?;
-        }
     }
-    if let Some(rest) = tokenizer_dec.decode_rest().map_err(E::msg)? {
-        print!("{rest}");
-    }
-
+    println!(
+        "{}",
+        tokenizer_dec.decode(&token_ids, true).map_err(E::msg)?
+    );
     Ok(())
 }