Add the quantized mpt model. (#1123)

* Add the quantized mpt model.

* Support the quantized model for replit-code.

candle-examples/examples/replit-code/main.rs

@@ -7,7 +7,8 @@ extern crate accelerate_src;
 use anyhow::{Error as E, Result};
 use clap::Parser;
 
-use candle_transformers::models::mpt::{Config, Model};
+use candle_transformers::models::mpt::{Config, Model as M};
+use candle_transformers::models::quantized_mpt::Model as Q;
 
 use candle::{DType, Device, Tensor};
 use candle_nn::VarBuilder;
@@ -15,6 +16,20 @@ use candle_transformers::generation::LogitsProcessor;
 use hf_hub::{api::sync::Api, Repo, RepoType};
 use tokenizers::Tokenizer;
 
+enum Model {
+    M(M),
+    Q(Q),
+}
+
+impl Model {
+    fn forward(&mut self, xs: &Tensor) -> candle::Result<Tensor> {
+        match self {
+            Self::M(model) => model.forward(xs),
+            Self::Q(model) => model.forward(xs),
+        }
+    }
+}
+
 struct TextGeneration {
     model: Model,
     device: Device,
@@ -148,6 +163,9 @@ struct Args {
     #[arg(long)]
     revision: Option<String>,
 
+    #[arg(long)]
+    quantized: bool,
+
     #[arg(long)]
     weight_file: Option<String>,
 
@@ -206,16 +224,29 @@ fn main() -> Result<()> {
     };
     let filename = match args.weight_file {
         Some(weight_file) => std::path::PathBuf::from(weight_file),
-        None => repo.get("model.safetensors")?,
+        None => {
+            if args.quantized {
+                repo.get("model-replit-code-v1_5-q4k.gguf")?
+            } else {
+                repo.get("model.safetensors")?
+            }
+        }
     };
     println!("retrieved the files in {:?}", start.elapsed());
     let tokenizer = Tokenizer::from_file(tokenizer_filename).map_err(E::msg)?;
 
     let start = std::time::Instant::now();
     let config = Config::replit_code_v1_5_3b();
-    let device = candle_examples::device(args.cpu)?;
-    let vb = unsafe { VarBuilder::from_mmaped_safetensors(&[filename], DType::F32, &device)? };
-    let model = Model::new(&config, vb.pp("transformer"))?;
+    let (model, device) = if args.quantized {
+        let vb = candle_transformers::quantized_var_builder::VarBuilder::from_gguf(&filename)?;
+        let model = Model::Q(Q::new(&config, vb.pp("transformer"))?);
+        (model, Device::Cpu)
+    } else {
+        let device = candle_examples::device(args.cpu)?;
+        let vb = unsafe { VarBuilder::from_mmaped_safetensors(&[filename], DType::F32, &device)? };
+        let model = Model::M(M::new(&config, vb.pp("transformer"))?);
+        (model, device)
+    };
     println!("loaded the model in {:?}", start.elapsed());
 
     let mut pipeline = TextGeneration::new(