Add a RotatingKVCache. (#2493)

* Add a RotatingKVCache.

* Add some KvCache tests.

* Test the reset too.

* More kv-cache testing.

* More tests for the rotating kv-cache.

* Improve the api for the rotating cache so that the whole src tensor gets returned when it's overlarge.

* Handle contiguity + bugfix + use in mimi.

* Add a way to test the mimi streaming mode.

* Mimi streaming fixes.

* More rotating kv-cache.

* Fix the attn mask generation.

* Handle the abs case.

* Add some tests for the generated mask.

candle-examples/examples/mimi/main.rs

@@ -39,6 +39,11 @@ struct Args {
     /// The model weight file, in safetensor format.
     #[arg(long)]
     model: Option<String>,
+
+    /// Whether to use streaming or not, when streaming slices of data of the given size are passed
+    /// to the encoder/decoder one at a time.
+    #[arg(long)]
+    streaming: Option<usize>,
 }
 
 fn main() -> Result<()> {
@@ -87,20 +92,49 @@ fn main() -> Result<()> {
                     pcm
                 }
             };
-            let pcm_len = pcm.len();
-            let pcm = Tensor::from_vec(pcm, (1, 1, pcm_len), &device)?;
-            println!("input pcm shape: {:?}", pcm.shape());
-            model.encode(&pcm)?
+            match args.streaming {
+                Some(chunk_size) => {
+                    let mut code_chunks = vec![];
+                    for pcm in pcm.chunks(chunk_size) {
+                        let pcm = Tensor::new(pcm, &device)?.reshape((1, 1, ()))?;
+                        let code_chunk = model.encode(&pcm)?;
+                        code_chunks.push(code_chunk)
+                    }
+                    Tensor::cat(&code_chunks, candle::D::Minus1)?
+                }
+                None => {
+                    let pcm_len = pcm.len();
+                    let pcm = Tensor::from_vec(pcm, (1, 1, pcm_len), &device)?;
+                    println!("input pcm shape: {:?}", pcm.shape());
+                    model.encode(&pcm)?
+                }
+            }
         }
     };
     println!("codes shape: {:?}", codes.shape());
+    model.reset_state();
 
     match args.action {
         Action::AudioToCode => {
             codes.save_safetensors("codes", &args.out_file)?;
         }
         Action::AudioToAudio | Action::CodeToAudio => {
-            let pcm = model.decode(&codes)?;
+            let pcm = match args.streaming {
+                Some(chunk_size) => {
+                    let seq_len = codes.dim(candle::D::Minus1)?;
+                    let mut pcm_chunks = vec![];
+                    for chunk_start in (0..seq_len).step_by(chunk_size) {
+                        let chunk_len = usize::min(chunk_size, seq_len - chunk_start);
+                        let codes = codes.narrow(candle::D::Minus1, chunk_start, chunk_len)?;
+                        let pcm = model.decode_step(&codes.into())?;
+                        if let Some(pcm) = pcm.as_option() {
+                            pcm_chunks.push(pcm.clone())
+                        }
+                    }
+                    Tensor::cat(&pcm_chunks, candle::D::Minus1)?
+                }
+                None => model.decode(&codes)?,
+            };
             println!("output pcm shape: {:?}", pcm.shape());
             let pcm = pcm.i(0)?.i(0)?;
             let pcm = candle_examples::audio::normalize_loudness(&pcm, 24_000, true)?;

candle-nn/src/kv_cache.rs

@@ -1,4 +1,4 @@
-use candle::{Result, Tensor};
+use candle::{Device, Result, Tensor};
 
 #[derive(Debug, Clone)]
 pub struct Cache {
@@ -145,3 +145,225 @@ impl KvCache {
         self.v.reset();
     }
 }
+
+#[derive(Debug, Clone)]
+pub struct RotatingCache {
+    all_data: Option<Tensor>,
+    dim: usize,
+    // `offset` is the current write index in the buffer
+    offset: usize,
+    // The total size of the sequence seen so far.
+    current_seq_len: usize,
+    // max_seq_len is the size of the rotating buffer, it is actually allowed for the full
+    // sequence to grow past this limit.
+    max_seq_len: usize,
+}
+
+impl RotatingCache {
+    pub fn new(dim: usize, max_seq_len: usize) -> Self {
+        Self {
+            all_data: None,
+            dim,
+            offset: 0,
+            current_seq_len: 0,
+            max_seq_len,
+        }
+    }
+
+    pub fn offset(&self) -> usize {
+        self.offset
+    }
+
+    pub fn dim(&self) -> usize {
+        self.dim
+    }
+
+    pub fn current_seq_len(&self) -> usize {
+        self.current_seq_len
+    }
+
+    pub fn max_seq_len(&self) -> usize {
+        self.max_seq_len
+    }
+
+    pub fn all_data(&self) -> &Option<Tensor> {
+        &self.all_data
+    }
+
+    pub fn current_data(&self) -> Result<Option<Tensor>> {
+        let data = match self.all_data.as_ref() {
+            None => None,
+            Some(d) => {
+                if self.current_seq_len >= self.max_seq_len {
+                    Some(d.clone())
+                } else {
+                    Some(d.narrow(self.dim, 0, self.current_seq_len)?)
+                }
+            }
+        };
+        Ok(data)
+    }
+
+    pub fn reset(&mut self) {
+        self.offset = 0;
+        self.current_seq_len = 0;
+        self.all_data = None;
+    }
+
+    pub fn append(&mut self, src: &Tensor) -> Result<Tensor> {
+        let seq_len = src.dim(self.dim)?;
+        // This doesn't seem very idiomatic but because the creation can fail, it's tricky to use
+        // self.all_data.get_or_insert_with.
+        if self.all_data.is_none() {
+            let mut shape = src.dims().to_vec();
+            shape[self.dim] = self.max_seq_len;
+            let ad = Tensor::zeros(shape, src.dtype(), src.device())?;
+            self.all_data = Some(ad)
+        };
+        let ad = self.all_data.as_mut().unwrap();
+
+        self.current_seq_len += seq_len;
+        if seq_len >= self.max_seq_len {
+            let to_copy = src
+                .narrow(self.dim, seq_len - self.max_seq_len, self.max_seq_len)?
+                .contiguous()?;
+            ad.slice_set(&to_copy, self.dim, 0)?;
+            self.offset = 0;
+            // Here we return `src` rather than `ad` so that all the past can be used.
+            Ok(src.clone())
+        } else {
+            let rem_len = self.max_seq_len - self.offset;
+            if seq_len <= rem_len {
+                ad.slice_set(&src.contiguous()?, self.dim, self.offset)?;
+                self.offset = (self.offset + seq_len) % self.max_seq_len;
+            } else {
+                // We have to make two copies here as we go over the boundary of the cache.
+                if rem_len > 0 {
+                    let src1 = src.narrow(self.dim, 0, rem_len)?.contiguous()?;
+                    ad.slice_set(&src1, self.dim, self.offset)?;
+                }
+                let src2 = src
+                    .narrow(self.dim, rem_len, seq_len - rem_len)?
+                    .contiguous()?;
+                ad.slice_set(&src2, self.dim, 0)?;
+                self.offset = seq_len - rem_len;
+            }
+            if self.current_seq_len >= self.max_seq_len {
+                Ok(ad.clone())
+            } else {
+                Ok(ad.narrow(self.dim, 0, self.current_seq_len)?)
+            }
+        }
+    }
+
+    fn get_mask_abs(&self, size1: usize, size2: usize, device: &Device) -> Result<Tensor> {
+        let context = self.max_seq_len;
+        let mask: Vec<_> = (0..size1)
+            .flat_map(|i| {
+                (0..size2).map(move |j| {
+                    u8::from(size1 + j > size2 + i || size1 + j + context < size2 + i)
+                })
+            })
+            .collect();
+        Tensor::from_slice(&mask, (size1, size2), device)
+    }
+
+    fn get_mask_rel(&self, size1: usize, size2: usize, device: &Device) -> Result<Tensor> {
+        let context = self.max_seq_len;
+        let upd_offset = (self.offset + size1) % self.max_seq_len;
+        let mask: Vec<_> = (0..size1)
+            .flat_map(|pos_src| {
+                // The absolute position of the elements that will get added to the cache.
+                let pos_src = self.current_seq_len + pos_src;
+                (0..size2).map(move |pos_cache_rel| {
+                    // The absolute position of the cache elements after the addition.
+                    let pos_cache = self.current_seq_len + size1 + pos_cache_rel - upd_offset;
+                    let pos_cache = if pos_cache_rel < upd_offset {
+                        pos_cache
+                    } else {
+                        pos_cache - self.max_seq_len
+                    };
+                    u8::from(pos_cache > pos_src || pos_cache + context < pos_src)
+                })
+            })
+            .collect();
+        Tensor::from_slice(&mask, (size1, size2), device)
+    }
+
+    /// Returns the attn_mask to be applied *after* adding `seq_len` to the cache.
+    pub fn attn_mask(&self, seq_len: usize, device: &Device) -> Result<Option<Tensor>> {
+        let mask = if seq_len == 1 {
+            None
+        } else {
+            let mask = if seq_len < self.max_seq_len {
+                let cache_out_len = (self.current_seq_len + seq_len).min(self.max_seq_len);
+                self.get_mask_rel(seq_len, cache_out_len, device)?
+            } else {
+                self.get_mask_abs(seq_len, seq_len, device)?
+            };
+            Some(mask)
+        };
+        Ok(mask)
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct RotatingKvCache {
+    k: RotatingCache,
+    v: RotatingCache,
+}
+
+impl RotatingKvCache {
+    pub fn new(dim: usize, max_seq_len: usize) -> Self {
+        let k = RotatingCache::new(dim, max_seq_len);
+        let v = RotatingCache::new(dim, max_seq_len);
+        Self { k, v }
+    }
+
+    pub fn k_cache(&self) -> &RotatingCache {
+        &self.k
+    }
+
+    pub fn v_cache(&self) -> &RotatingCache {
+        &self.v
+    }
+
+    pub fn k_cache_mut(&mut self) -> &mut RotatingCache {
+        &mut self.k
+    }
+
+    pub fn v_cache_mut(&mut self) -> &mut RotatingCache {
+        &mut self.v
+    }
+
+    pub fn k(&self) -> Result<Option<Tensor>> {
+        self.k.current_data()
+    }
+
+    pub fn v(&self) -> Result<Option<Tensor>> {
+        self.v.current_data()
+    }
+
+    pub fn append(&mut self, k: &Tensor, v: &Tensor) -> Result<(Tensor, Tensor)> {
+        let out_k = self.k.append(k)?;
+        let out_v = self.v.append(v)?;
+        Ok((out_k, out_v))
+    }
+
+    pub fn offset(&self) -> usize {
+        self.k.offset()
+    }
+
+    pub fn current_seq_len(&self) -> usize {
+        self.k.current_seq_len()
+    }
+
+    pub fn attn_mask(&self, seq_len: usize, device: &Device) -> Result<Option<Tensor>> {
+        self.k.attn_mask(seq_len, device)
+    }
+
+    pub fn reset(&mut self) {
+        self.k.reset();
+        self.v.reset();
+    }
+}