Config object for StaticAttentionIOManager and decoding helper (#12379)

Summary:
Pull Request resolved: #12379

- Group individual config variables into a configuration object.
- Add a simple decoding helper in preparation for lookahead decoding next.

Reviewed By: billmguo

Differential Revision: D78113341

Author: sxu

examples/models/llama/runner/static_attention_io_manager.h

@@ -168,6 +168,10 @@ class StaticKVCache {
     }
   }
 
+  size_t size() {
+    return valid_len_;
+  }
+
  private:
   void init_ptrs() {
     input_ptrs_.resize(n_caches_);
@@ -339,26 +343,40 @@ template <
     typename MaskAllocatorT = std::allocator<MaskT>>
 class StaticAttentionIOManager {
  public:
-  StaticAttentionIOManager(
-      size_t n_caches,
-      size_t cache_len,
-      size_t head_dim,
-      size_t max_input_len,
-      size_t rope_freqs_cos_index,
-      size_t rope_freqs_sin_index,
-      RopeT* rope_freqs_cos,
-      RopeT* rope_freqs_sin,
-      StaticAttentionUpdateStyle style =
-          StaticAttentionUpdateStyle::SLIDING_CACHE)
-      : cache_len_(cache_len),
-        head_dim_(head_dim),
-        style_(style),
-        kCaches_(n_caches, cache_len, head_dim, max_input_len, false, style),
-        vCaches_(n_caches, cache_len, head_dim, max_input_len, false, style),
-        rope_freqs_cos_index_(rope_freqs_cos_index),
-        rope_freqs_sin_index_(rope_freqs_sin_index),
-        rope_freqs_cos_(rope_freqs_cos),
-        rope_freqs_sin_(rope_freqs_sin) {}
+  struct StaticAttentionIOConfig {
+    size_t n_caches{};
+    size_t cache_len{};
+    size_t head_dim{};
+    size_t max_input_len{};
+    size_t attn_mask_input_index{};
+    size_t rope_freqs_cos_input_index{};
+    size_t rope_freqs_sin_input_index{};
+    std::vector<size_t> k_cache_input_indices;
+    std::vector<size_t> k_cache_output_indices;
+    std::vector<size_t> v_cache_input_indices;
+    std::vector<size_t> v_cache_output_indices;
+    RopeT* rope_freqs_cos;
+    RopeT* rope_freqs_sin;
+    StaticAttentionUpdateStyle style =
+        StaticAttentionUpdateStyle::SLIDING_CACHE;
+  };
+
+  StaticAttentionIOManager(StaticAttentionIOConfig config)
+      : config_(std::move(config)),
+        kCaches_(
+            config_.n_caches,
+            config_.cache_len,
+            config_.head_dim,
+            config_.max_input_len,
+            false,
+            config_.style),
+        vCaches_(
+            config_.n_caches,
+            config_.cache_len,
+            config_.head_dim,
+            config_.max_input_len,
+            false,
+            config_.style) {}
 
   /**
    * Create a new StaticAttentionMask that will be managed by this object.
@@ -369,36 +387,38 @@ class StaticAttentionIOManager {
         std::piecewise_construct,
         std::forward_as_tuple(input_len),
         std::forward_as_tuple(
-            cache_len_, input_len, head_dim_, zero_val, mask_val, style_));
+            config_.cache_len,
+            input_len,
+            config_.head_dim,
+            zero_val,
+            mask_val,
+            config_.style));
     return it.first->second;
   }
 
   /**
    * Retrieve a mask suitable for given input length.
    */
-  StaticAttentionMask<MaskT, MaskAllocatorT>& getMask(size_t input_len) {
+  StaticAttentionMask<MaskT, MaskAllocatorT>& get_mask(size_t input_len) {
     return attentionMasks_.at(input_len);
   }
 
   /**
    * Set I/O pointers for KV cache and RoPE freqencies.
    */
-  void prepare(
-      torch::executor::Method& method,
-      const std::vector<size_t>& k_cache_input_indices,
-      const std::vector<size_t>& k_cache_output_indices,
-      const std::vector<size_t>& v_cache_input_indices,
-      const std::vector<size_t>& v_cache_output_indices) {
-    kCaches_.prepare(method, k_cache_input_indices, k_cache_output_indices);
-    vCaches_.prepare(method, v_cache_input_indices, v_cache_output_indices);
+  void prepare(torch::executor::Method& method) {
+    kCaches_.prepare(
+        method, config_.k_cache_input_indices, config_.k_cache_output_indices);
+    vCaches_.prepare(
+        method, config_.v_cache_input_indices, config_.v_cache_output_indices);
     set_input(
         method,
-        rope_freqs_cos_index_,
-        rope_freqs_cos_ + input_pos_ * head_dim_ / 2);
+        config_.rope_freqs_cos_input_index,
+        config_.rope_freqs_cos + input_pos_ * config_.head_dim / 2);
     set_input(
         method,
-        rope_freqs_sin_index_,
-        rope_freqs_sin_ + input_pos_ * head_dim_ / 2);
+        config_.rope_freqs_sin_input_index,
+        config_.rope_freqs_sin + input_pos_ * config_.head_dim / 2);
   }
 
   /**
@@ -430,6 +450,36 @@ class StaticAttentionIOManager {
     }
   }
 
+  template <typename TokenT>
+  std::vector<TokenT> decode(
+      TokenT prev_tok,
+      executorch::runtime::Span<TokenT> input_buffer,
+      executorch::runtime::Method& method,
+      std::function<TokenT(executorch::runtime::Method&)>& sample,
+      std::function<bool(TokenT)>& should_stop) {
+    set_input(method, 0, input_buffer.data());
+    auto& mask = get_mask(input_buffer.size());
+    set_input(method, config_.attn_mask_input_index, mask.get());
+
+    std::vector<TokenT> generated_tokens;
+    while (kCaches_.size() + 1 <= config_.cache_len) {
+      input_buffer[0] = prev_tok;
+      prepare(method);
+      ET_CHECK(method.execute() == executorch::runtime::Error::Ok);
+      update(
+          method,
+          config_.k_cache_output_indices,
+          config_.v_cache_output_indices,
+          1);
+      prev_tok = sample(method);
+      generated_tokens.emplace_back(prev_tok);
+      if (should_stop(prev_tok)) {
+        break;
+      }
+    }
+    return generated_tokens;
+  }
+
  private:
   template <typename T>
   void set_input(executorch::runtime::Method& method, size_t idx, T* data) {
@@ -447,19 +497,12 @@ class StaticAttentionIOManager {
     ET_CHECK(method.set_input(t, idx) == executorch::runtime::Error::Ok);
   }
 
-  size_t cache_len_;
-  size_t input_len_;
-  size_t head_dim_;
+  StaticAttentionIOConfig config_;
   size_t input_pos_;
-  StaticAttentionUpdateStyle style_;
   StaticKVCache<CacheT, CacheAllocatorT> kCaches_;
   StaticKVCache<CacheT, CacheAllocatorT> vCaches_;
   std::unordered_map<size_t, StaticAttentionMask<MaskT, MaskAllocatorT>>
       attentionMasks_;
-  size_t rope_freqs_cos_index_;
-  size_t rope_freqs_sin_index_;
-  RopeT* rope_freqs_cos_;
-  RopeT* rope_freqs_sin_;
 };
 
 } // namespace example