Expose some helper functions to create quantized models. (#1837)

candle-transformers/src/models/with_tracing.rs

@@ -116,6 +116,12 @@ impl QMatMul {
         let span = tracing::span!(tracing::Level::TRACE, "qmatmul");
         Ok(Self { inner, span })
     }
+
+    pub fn from_weights(ws: std::sync::Arc<candle::quantized::QTensor>) -> Result<Self> {
+        let inner = candle::quantized::QMatMul::from_arc(ws)?;
+        let span = tracing::span!(tracing::Level::TRACE, "qmatmul");
+        Ok(Self { inner, span })
+    }
 }
 
 impl Module for QMatMul {

candle-transformers/src/quantized_nn.rs

@@ -35,6 +35,14 @@ pub struct Linear {
 }
 
 impl Linear {
+    pub fn from_arc(
+        weight: std::sync::Arc<candle::quantized::QTensor>,
+        bias: Option<Tensor>,
+    ) -> Result<Self> {
+        let weight = QMatMul::from_weights(weight)?;
+        Ok(Self { weight, bias })
+    }
+
     pub fn from_weights(weight: QMatMul, bias: Option<Tensor>) -> Self {
         Self { weight, bias }
     }

candle-transformers/src/quantized_var_builder.rs

@@ -3,6 +3,7 @@ use candle::{Device, Result, Shape};
 use std::sync::Arc;
 
 // VarBuilder specialized for QTensors
+#[derive(Clone)]
 pub struct VarBuilder {
     data: Arc<std::collections::HashMap<String, Arc<QTensor>>>,
     path: Vec<String>,