Method cache_activation

cake-core/src/backends/vulkan/mod.rs:552–563

Cache a dispatch output buffer by the returned Tensor's TensorId. If the next dispatch consumes this tensor, `get_or_upload` will find the buffer here and skip the re-upload.

(&self, tensor_id: TensorId, buf: MappedBuffer)

    /// If the next dispatch consumes this tensor, `get_or_upload` will find
    /// the buffer here and skip the re-upload.
    fn cache_activation(&self, tensor_id: TensorId, buf: MappedBuffer) {
        let buf = Arc::new(buf);
        let mut act_cache = self.activation_cache.lock().unwrap();
        if act_cache.len() >= 16 {
            // Evict oldest entry, release its buffer back to pool
            let (_, old_buf) = act_cache.remove(0);
            if let Ok(old) = Arc::try_unwrap(old_buf) {
                self.release_output(old);
            }
        }
        act_cache.push((tensor_id, buf));
    }

    /// Compute a stable cache key from tensor's storage pointer + layout.
    /// Survives `.t()` calls which create new TensorIds but share storage.