From 778b71fc93cf1cc541cabfddbd1b229898229506 Mon Sep 17 00:00:00 2001
From: baiyf <baiyfbupt@gmail.com>
Date: Wed, 27 Jun 2018 16:51:42 +0800
Subject: [PATCH] Optimize bipartite_match_op in large scale input (#11730)

* optimize bipartite_match_op in large scale input
---
 .../operators/detection/bipartite_match_op.cc | 98 +++++++++++++------
 .../unittests/test_bipartite_match_op.py      | 17 ++++
 2 files changed, 84 insertions(+), 31 deletions(-)

diff --git a/paddle/fluid/operators/detection/bipartite_match_op.cc b/paddle/fluid/operators/detection/bipartite_match_op.cc
index d437ad5c198..c23b65fe4de 100644
--- a/paddle/fluid/operators/detection/bipartite_match_op.cc
+++ b/paddle/fluid/operators/detection/bipartite_match_op.cc
@@ -51,6 +51,12 @@ class BipartiteMatchOp : public framework::OperatorWithKernel {
   }
 };
 
+template <class T>
+bool DistPairDescend(std::tuple<int, int, T> pair1,
+                     std::tuple<int, int, T> pair2) {
+  return std::get<2>(pair1) > std::get<2>(pair2);
+}
+
 template <typename T>
 class BipartiteMatchKernel : public framework::OpKernel<T> {
  public:
@@ -58,46 +64,76 @@ class BipartiteMatchKernel : public framework::OpKernel<T> {
   // The match_dist must be initialized to 0 at first.
   void BipartiteMatch(const Tensor& dist, int* match_indices,
                       T* match_dist) const {
-    constexpr T kEPS = static_cast<T>(1e-6);
     PADDLE_ENFORCE_EQ(dist.dims().size(), 2, "The rank of dist must be 2.");
     int64_t row = dist.dims()[0];
     int64_t col = dist.dims()[1];
     auto* dist_data = dist.data<T>();
-    std::vector<int> row_pool;
-    for (int i = 0; i < row; ++i) {
-      row_pool.push_back(i);
-    }
-    while (row_pool.size() > 0) {
-      int max_idx = -1;
-      int max_row_idx = -1;
-      T max_dist = -1;
-      for (int64_t j = 0; j < col; ++j) {
-        if (match_indices[j] != -1) {
-          continue;
+    // Test result: When row==130 the speed of these two methods almost the same
+    if (row >= 130) {
+      std::vector<std::tuple<int, int, T>> match_pair;
+
+      for (int64_t i = 0; i < row; ++i) {
+        for (int64_t j = 0; j < col; ++j) {
+          match_pair.push_back(std::make_tuple(i, j, dist_data[i * col + j]));
         }
-        for (size_t k = 0; k < row_pool.size(); ++k) {
-          int m = row_pool[k];
-          // distance is 0 between m-th row and j-th column
-          if (dist_data[m * col + j] < kEPS) {
+      }
+      std::sort(match_pair.begin(), match_pair.end(), DistPairDescend<T>);
+      std::vector<int> row_indices(row, -1);
+
+      int64_t idx = 0;
+      for (int64_t k = 0; k < row * col; ++k) {
+        int64_t i = std::get<0>(match_pair[k]);
+        int64_t j = std::get<1>(match_pair[k]);
+        T dist = std::get<2>(match_pair[k]);
+
+        if (idx >= row) {
+          break;
+        }
+        if (match_indices[j] == -1 && row_indices[i] == -1 && dist > 0) {
+          match_indices[j] = i;
+          row_indices[i] = j;
+          match_dist[j] = dist;
+          idx += 1;
+        }
+      }
+    } else {
+      constexpr T kEPS = static_cast<T>(1e-6);
+      std::vector<int> row_pool;
+      for (int i = 0; i < row; ++i) {
+        row_pool.push_back(i);
+      }
+      while (row_pool.size() > 0) {
+        int max_idx = -1;
+        int max_row_idx = -1;
+        T max_dist = -1;
+        for (int64_t j = 0; j < col; ++j) {
+          if (match_indices[j] != -1) {
             continue;
           }
-          if (dist_data[m * col + j] > max_dist) {
-            max_idx = j;
-            max_row_idx = m;
-            max_dist = dist_data[m * col + j];
+          for (size_t k = 0; k < row_pool.size(); ++k) {
+            int m = row_pool[k];
+            // distance is 0 between m-th row and j-th column
+            if (dist_data[m * col + j] < kEPS) {
+              continue;
+            }
+            if (dist_data[m * col + j] > max_dist) {
+              max_idx = j;
+              max_row_idx = m;
+              max_dist = dist_data[m * col + j];
+            }
           }
         }
-      }
-      if (max_idx == -1) {
-        // Cannot find good match.
-        break;
-      } else {
-        PADDLE_ENFORCE_EQ(match_indices[max_idx], -1);
-        match_indices[max_idx] = max_row_idx;
-        match_dist[max_idx] = max_dist;
-        // Erase the row index.
-        row_pool.erase(
-            std::find(row_pool.begin(), row_pool.end(), max_row_idx));
+        if (max_idx == -1) {
+          // Cannot find good match.
+          break;
+        } else {
+          PADDLE_ENFORCE_EQ(match_indices[max_idx], -1);
+          match_indices[max_idx] = max_row_idx;
+          match_dist[max_idx] = max_dist;
+          // Erase the row index.
+          row_pool.erase(
+              std::find(row_pool.begin(), row_pool.end(), max_row_idx));
+        }
       }
     }
   }
diff --git a/python/paddle/fluid/tests/unittests/test_bipartite_match_op.py b/python/paddle/fluid/tests/unittests/test_bipartite_match_op.py
index 1a245fd756c..d5bd726c4a8 100644
--- a/python/paddle/fluid/tests/unittests/test_bipartite_match_op.py
+++ b/python/paddle/fluid/tests/unittests/test_bipartite_match_op.py
@@ -114,6 +114,23 @@ class TestBipartiteMatchOpWithoutLoD(OpTest):
         self.check_output()
 
 
+class TestBipartiteMatchOpWithoutLoDLargeScaleInput(OpTest):
+    def setUp(self):
+        self.op_type = 'bipartite_match'
+        lod = [[300]]
+        dist = np.random.random((300, 17)).astype('float32')
+        match_indices, match_dist = batch_bipartite_match(dist, lod[0])
+
+        self.inputs = {'DistMat': dist}
+        self.outputs = {
+            'ColToRowMatchIndices': match_indices,
+            'ColToRowMatchDist': match_dist,
+        }
+
+    def test_check_output(self):
+        self.check_output()
+
+
 class TestBipartiteMatchOpWithPerPredictionType(OpTest):
     def setUp(self):
         self.op_type = 'bipartite_match'
-- 
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