[ET-VK] Add 2D Reduction to Vulkan Backend

alexdean08 · alexdean08 · commit b9e001b6a68f · 2025-07-25T10:31:42.000-07:00
diff --git a/backends/vulkan/op_registry.py b/backends/vulkan/op_registry.py
@@ -532,7 +532,7 @@ def register_reduce_op(features: OpFeatures):
 
     def check_reduce_node(node: torch.fx.Node) -> bool:
         dim_list = node.args[1]
-        if isinstance(dim_list, list) and len(dim_list) != 1:
+        if isinstance(dim_list, list) and len(dim_list) > 2:
             return False
 
         keepdim = node.args[2]
diff --git a/backends/vulkan/runtime/graph/ops/glsl/reduce2d.glsl b/backends/vulkan/runtime/graph/ops/glsl/reduce2d.glsl
@@ -0,0 +1,128 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#version 450 core
+
+#define PRECISION ${PRECISION}
+#define VEC4_T ${texel_load_type(DTYPE, STORAGE)}
+
+${define_active_storage_type(STORAGE)}
+
+#extension GL_EXT_control_flow_attributes : require
+
+layout(std430) buffer;
+
+${layout_declare_tensor(B, "w", "tout", DTYPE, STORAGE)}
+${layout_declare_tensor(B, "r", "tin", DTYPE, STORAGE)}
+
+${layout_declare_ubo(B, "ivec3", "tin_limits")}
+${layout_declare_ubo(B, "ivec4", "tin_sizes")}
+
+layout(local_size_x_id = 0, local_size_y_id = 1, local_size_z_id = 2) in;
+
+layout(constant_id = 3) const int packed_dim = 0;
+layout(constant_id = 4) const int reduce_dim1 = 0;
+layout(constant_id = 5) const int reduce_dim2 = 1;
+layout(constant_id = 6) const int group_dim = 2;
+
+// A more verbose name would be NWORKERS_PER_GROUP. This describes the number of
+// threads that will co-operate to compute one reduction output. There may be
+// multiple groups computing distinct reduction outputs within one work group.
+#define NWORKERS 4
+
+// Sets an upper limit on the total size of a work group based on how many
+// elements are allocated in the shared memory array below. Each thread in the
+// work group will write into its assigned element in the shared array.
+#define MAX_NTHREADS 16
+
+
+shared vec4 shared_vecs[MAX_NTHREADS];
+
+#include "indexing_utils.h"
+
+int tid_to_smi(const ivec2 tid) {
+  return tid.x + tid.y * NWORKERS;
+}
+
+// Initializing the accumulator accepts the first value in the reduction row,
+// since some reduction operations (i.e. amax, amin) prefer to initialize with
+// a data point instead of a static value.
+#define INIT_ACCUM(first_val) ${INIT_ACCUM}
+#define UPDATE_ACCUM(accum, new_val) ${UPDATE_ACCUM}
+// Useful for operators such as mean which want to perform a final calculation
+// with the accumulator.
+#define POSTPROCESS(accum) ${POSTPROCESS}
+
+void reduce_2d(const ivec2 tid, ivec3 scan_pos) {
+  // shared memory index of this thread
+  const int smi = tid_to_smi(tid);
+
+  scan_pos[reduce_dim1] = 0;
+  scan_pos[reduce_dim2] = 0;
+  vec4 accum = INIT_ACCUM(load_texel(tin, scan_pos));
+  
+  // First dimension reduction
+  scan_pos[reduce_dim1] = tid.x;
+  for (int i = tid.x; i < tin_sizes[reduce_dim1]; 
+       i += NWORKERS, scan_pos[reduce_dim1] += NWORKERS) {
+    
+    // Second dimension reduction
+    scan_pos[reduce_dim2] = 0;
+    for (int j = 0; j < tin_sizes[reduce_dim2]; j++, scan_pos[reduce_dim2]++) {
+      accum = UPDATE_ACCUM(accum, load_texel(tin, scan_pos));
+    }
+  }
+  
+  // Write partial output to shared memory and synchronize
+  shared_vecs[smi] = accum;
+  barrier();
+  
+  // Main thread aggregates results
+  if (tid.x == 0) {
+    // Iterate over the partial outputs to obtain the overall output
+    int group_i = tid.y * NWORKERS;
+    accum = shared_vecs[group_i++];
+    for (int i = 1; i < NWORKERS; i++, group_i++) {
+      accum = UPDATE_ACCUM(accum, shared_vecs[group_i]);
+    }
+    
+    // Determine if there are any padding elements in the final texel of the
+    // packed dimension
+    const int nspill = mod4(tin_sizes[packed_dim]);
+    // Detect if this thread is working on the final texels of the packed
+    // dimension, which may have padding elements
+    const bool is_last_texel = 
+        scan_pos[packed_dim] == (tin_limits[packed_dim] - 1);
+    
+    // Explicitly set padding elements to 0
+    if (is_last_texel && nspill > 0) {
+      [[unroll]] for (int i = nspill; i < 4; i++) {
+        accum[i] = 0;
+      }
+    }
+    scan_pos[reduce_dim1] = 0;
+    scan_pos[reduce_dim2] = 0;
+    write_texel(tout, scan_pos, POSTPROCESS(accum));
+  }
+}
+
+void main() {
+  ivec3 scan_pos = ivec3(gl_GlobalInvocationID);
+  scan_pos[reduce_dim1] = 0;
+  scan_pos[reduce_dim2] = 0;
+
+  const ivec2 tid = ivec2(
+      gl_LocalInvocationID[reduce_dim1],
+      gl_LocalInvocationID[group_dim]);
+
+  if (any(greaterThanEqual(scan_pos, tin_limits))) {
+    return;
+  }
+
+  reduce_2d(tid, scan_pos);
+}
diff --git a/backends/vulkan/runtime/graph/ops/glsl/reduce2d.yaml b/backends/vulkan/runtime/graph/ops/glsl/reduce2d.yaml
@@ -0,0 +1,29 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+reduce2d:
+  parameter_names_with_default_values:
+    DTYPE: float
+    STORAGE: texture3d
+    INIT_ACCUM: VEC4_T(0)
+    UPDATE_ACCUM: accum + new_val
+    POSTPROCESS: accum
+  generate_variant_forall:
+    DTYPE:
+      - VALUE: half
+      - VALUE: float
+  shader_variants:
+    - NAME: sum2d
+    - NAME: mean2d
+      POSTPROCESS: (accum / (tin_sizes[reduce_dim1] * tin_sizes[reduce_dim2]))
+    - NAME: amax2d
+      INIT_ACCUM: first_val
+      UPDATE_ACCUM: max(accum, new_val)
+      POSTPROCESS: accum
+    - NAME: amin2d
+      INIT_ACCUM: first_val
+      UPDATE_ACCUM: min(accum, new_val)
+      POSTPROCESS: accum
diff --git a/backends/vulkan/runtime/graph/ops/impl/Reduce.cpp b/backends/vulkan/runtime/graph/ops/impl/Reduce.cpp
@@ -32,6 +32,24 @@ void resize_reduce_node(
   out->virtual_resize(new_sizes);
 }
 
+void resize_reduce2d_node(
+    ComputeGraph* graph,
+    const std::vector<ArgGroup>& args,
+    const std::vector<ValueRef>& resize_args) {
+  vTensorPtr out = graph->get_tensor(args[0].refs[0]);
+  vTensorPtr in = graph->get_tensor(args[1].refs[0]);
+
+  // Extract the dimensions to reduce over
+  const std::vector<int64_t> dims_list = graph->extract_int_or_symint_list(resize_args.at(0));
+  int32_t reduce_dim1_nchw = dims_list[0];
+  int32_t reduce_dim2_nchw = dims_list[1];
+
+  std::vector<int64_t> new_sizes = in->sizes();
+  new_sizes.at(normalize(reduce_dim1_nchw, new_sizes.size())) = 1;
+  new_sizes.at(normalize(reduce_dim2_nchw, new_sizes.size())) = 1;
+  out->virtual_resize(new_sizes);
+}
+
 utils::uvec3 reduce_global_wg_size(
     ComputeGraph* graph,
     const vkapi::ShaderInfo& shader,
@@ -137,15 +155,89 @@ void add_reduce_node(
       resize_reduce_node));
 }
 
+void add_reduce2d_node(
+    ComputeGraph& graph,
+    const ValueRef in,
+    const ValueRef dims_ref,
+    const ValueRef out,
+    const std::string& op_name) {
+  
+  VK_CHECK_COND(
+      !graph.is_buffer_storage(in) && !graph.is_buffer_storage(out),
+      "Vulkan reduction only supports texture storage");
+
+  const int64_t ndim = graph.dim_of(in);
+  
+  // Extract the two dimensions to reduce over
+  const std::vector<int64_t> dims_list = graph.extract_int_or_symint_list(dims_ref);
+  VK_CHECK_COND(dims_list.size() == 2, "reduce2d requires exactly 2 dimensions");
+  
+  int32_t reduce_dim1 = normalize(dims_list[0], ndim);
+  int32_t reduce_dim2 = normalize(dims_list[1], ndim);
+  
+  // Convert to WHCN format
+  reduce_dim1 = nchw_dim_to_whcn_dim(reduce_dim1, ndim);
+  reduce_dim2 = nchw_dim_to_whcn_dim(reduce_dim2, ndim);
+  
+  // Check that the concat dim is not one of the reduction dims
+  if (graph.dim_of(in) == 4 && graph.size_at<int>(0, in) > 1) {
+    VK_CHECK_COND(graph.concat_dim_of(in) != reduce_dim1);
+    VK_CHECK_COND(graph.concat_dim_of(in) != reduce_dim2);
+    VK_CHECK_COND(graph.concat_dim_of(out) != reduce_dim1);
+    VK_CHECK_COND(graph.concat_dim_of(out) != reduce_dim2);
+  }
+
+  std::string kernel_name = op_name + "2d";  // Add "2d" suffix
+  kernel_name.reserve(kShaderNameReserve);
+  add_dtype_suffix(kernel_name, graph.dtype_of(out));
+
+  // Calculate group_dim for specialization constants (use remaining dimension)
+  int32_t group_dim = 0;
+  for (int i = 0; i < 3; i++) {
+    if (i != reduce_dim1 && i != reduce_dim2) {
+      group_dim = i;
+      break;
+    }
+  }
+
+  const ValueRef reduce_dim1_whcn_ref = graph.get_or_add_value_for_int(reduce_dim1);
+  const ValueRef reduce_dim2_whcn_ref = graph.get_or_add_value_for_int(reduce_dim2);
+  const ValueRef group_dim_whcn_ref = graph.get_or_add_value_for_int(group_dim);
+
+  graph.execute_nodes().emplace_back(new DynamicDispatchNode(
+      graph,
+      VK_KERNEL_FROM_STR(kernel_name),
+      reduce_global_wg_size,
+      reduce_local_wg_size,
+      // Inputs and Outputs
+      {{out, vkapi::kWrite}, {in, vkapi::kRead}},
+      // Shader params buffers
+      {graph.logical_limits_ubo(in), graph.sizes_ubo(in)},
+      // Push Constants
+      {},
+      // Specialization Constants
+      {graph.packed_dim_of(out), reduce_dim1, reduce_dim2, group_dim},
+      // Resize Args
+      {dims_ref, reduce_dim1_whcn_ref, reduce_dim2_whcn_ref, group_dim_whcn_ref},
+      // Resizing Logic
+      resize_reduce2d_node));
+}
+
 #define DEFINE_REDUCE_FN(op_name, out_arg_idx)                           \
   void op_name(ComputeGraph& graph, const std::vector<ValueRef>& args) { \
     const std::vector<int64_t> dims_list =                               \
-        graph.extract_int_or_symint_list(args[1]);                       \
-    VK_CHECK_COND(dims_list.size() == 1);                                \
-    const int64_t dim_val = dims_list.at(0);                             \
-    const ValueRef dim_ref = graph.get_or_add_value_for_int(dim_val);    \
-    return add_reduce_node(                                              \
-        graph, args[0], dim_ref, args[out_arg_idx], #op_name);           \
+      graph.extract_int_or_symint_list(args[1]);                         \
+    if (dims_list.size() == 1) {                                         \
+      const int64_t dim_val = dims_list.at(0);                           \
+      const ValueRef dim_ref = graph.get_or_add_value_for_int(dim_val);  \
+      return add_reduce_node(                                            \
+          graph, args[0], dim_ref, args[out_arg_idx], #op_name);         \
+    } else if (dims_list.size() == 2) {                                  \
+      return add_reduce2d_node(                                          \
+          graph, args[0], args[1], args[out_arg_idx], #op_name);         \
+    } else {                                                             \
+      VK_CHECK_COND(false, "Only 1 or 2 dimensions supported");          \
+    }                                                                    \
   }
 
 DEFINE_REDUCE_FN(sum, 4)
