Add a dequantize command to tensor-tools. (#1565)

* Add a dequantize command to tensor-tools.

* Clippy fixes.

candle-core/examples/tensor-tools.rs

@@ -102,7 +102,7 @@ enum Command {
     },
 
     Quantize {
-        /// The input file, in gguf format.
+        /// The input file(s), in safetensors format.
         in_file: Vec<std::path::PathBuf>,
 
         /// The output file, in gguf format.
@@ -117,6 +117,15 @@ enum Command {
         #[arg(long, value_enum, default_value_t = QuantizationMode::Llama)]
         mode: QuantizationMode,
     },
+
+    Dequantize {
+        /// The input file, in gguf format.
+        in_file: std::path::PathBuf,
+
+        /// The output file, in safetensors format.
+        #[arg(long)]
+        out_file: std::path::PathBuf,
+    },
 }
 
 #[derive(Parser, Debug, Clone)]
@@ -285,6 +294,19 @@ fn run_quantize_safetensors(
     Ok(())
 }
 
+fn run_dequantize(in_file: std::path::PathBuf, out_file: std::path::PathBuf) -> Result<()> {
+    let mut in_file = std::fs::File::open(in_file)?;
+    let content = gguf_file::Content::read(&mut in_file)?;
+    let mut tensors = std::collections::HashMap::new();
+    for (tensor_name, _) in content.tensor_infos.iter() {
+        let tensor = content.tensor(&mut in_file, tensor_name)?;
+        let tensor = tensor.dequantize(&Device::Cpu)?;
+        tensors.insert(tensor_name.to_string(), tensor);
+    }
+    candle_core::safetensors::save(&tensors, out_file)?;
+    Ok(())
+}
+
 fn run_quantize(
     in_files: &[std::path::PathBuf],
     out_file: std::path::PathBuf,
@@ -379,6 +401,7 @@ fn main() -> anyhow::Result<()> {
             quantization,
             mode,
         } => run_quantize(&in_file, out_file, quantization, mode)?,
+        Command::Dequantize { in_file, out_file } => run_dequantize(in_file, out_file)?,
     }
     Ok(())
 }