xgboost

group_data.h
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1
14 #ifndef XGBOOST_COMMON_GROUP_DATA_H_
15 #define XGBOOST_COMMON_GROUP_DATA_H_
16
17 #include <cstddef>
18 #include <vector>
19 #include <algorithm>
20 #include <utility>
21
22 #include "xgboost/base.h"
23
24 namespace xgboost {
25 namespace common {
32 template<typename ValueType, typename SizeType = bst_ulong, bool is_row_major = false>
33 class ParallelGroupBuilder {
34 public:
45 ParallelGroupBuilder(std::vector<SizeType> *p_rptr,
46 std::vector<ValueType> *p_data,
47 size_t base_row_offset = 0)
48 : rptr_(*p_rptr),
49 data_(*p_data),
50 base_row_offset_(base_row_offset) {}
51
59 void InitBudget(std::size_t max_key, int nthread) {
60 thread_rptr_.resize(nthread);
61 const size_t full_size = is_row_major ? max_key : max_key - std::min(base_row_offset_, max_key);
62 thread_displacement_ = is_row_major ? full_size / nthread : 0;
63 for (std::size_t i = 0; i < thread_rptr_.size() - 1; ++i) {
64 const size_t thread_size = is_row_major ? thread_displacement_ : full_size;
65 thread_rptr_[i].resize(thread_size, 0);
66 }
67 const size_t last_thread_size = is_row_major ? (full_size - (nthread - 1)*thread_displacement_)
68 : full_size;
69 thread_rptr_[nthread - 1].resize(last_thread_size, 0);
70 }
71
78 void AddBudget(std::size_t key, int threadid, SizeType nelem = 1) {
79 std::vector<SizeType> &trptr = thread_rptr_[threadid];
80 size_t offset_key = is_row_major ? (key - base_row_offset_ - threadid*thread_displacement_)
81 : (key - base_row_offset_);
82 if (trptr.size() < offset_key + 1) {
83 trptr.resize(offset_key + 1, 0);
84 }
85 trptr[offset_key] += nelem;
86 }
87
89 inline void InitStorage() {
90 if (is_row_major) {
91 size_t expected_rows = 0;
92 for (std::size_t tid = 0; tid < thread_rptr_.size(); ++tid) {
93 expected_rows += thread_rptr_[tid].size();
94 }
95 // initialize rptr to be beginning of each segment
96 SizeType rptr_fill_value = rptr_.empty() ? 0 : rptr_.back();
97 rptr_.resize(expected_rows + base_row_offset_ + 1, rptr_fill_value);
98
99 std::size_t count = 0;
100 size_t offset_idx = base_row_offset_ + 1;
101 for (std::size_t tid = 0; tid < thread_rptr_.size(); ++tid) {
102 std::vector<SizeType> &trptr = thread_rptr_[tid];
103 for (std::size_t i = 0; i < trptr.size(); ++i) {
104 std::size_t thread_count = trptr[i]; // how many entries in this row
105 trptr[i] = count + rptr_fill_value;
106 count += thread_count;
107 if (offset_idx < rptr_.size()) {
108 rptr_[offset_idx++] += count;
109 }
110 }
111 }
112 data_.resize(rptr_.back()); // usage of empty allocator can help to improve performance
113 } else {
114 // set rptr to correct size
115 SizeType rptr_fill_value = rptr_.empty() ? 0 : rptr_.back();
116 for (std::size_t tid = 0; tid < thread_rptr_.size(); ++tid) {
117 if (rptr_.size() <= thread_rptr_[tid].size() + base_row_offset_) {
118 rptr_.resize(thread_rptr_[tid].size() + base_row_offset_ + 1,
119 rptr_fill_value); // key + 1
120 }
121 }
122 // initialize rptr to be beginning of each segment
123 std::size_t count = 0;
124 for (std::size_t i = base_row_offset_; i + 1 < rptr_.size(); ++i) {
125 for (std::size_t tid = 0; tid < thread_rptr_.size(); ++tid) {
126 std::vector<SizeType> &trptr = thread_rptr_[tid];
127 if (i < trptr.size() +
128 base_row_offset_) { // i^th row is assigned for this thread
129 std::size_t thread_count =
130 trptr[i - base_row_offset_]; // how many entries in this row
131 trptr[i - base_row_offset_] = count + rptr_.back();
132 count += thread_count;
133 }
134 }
135 rptr_[i + 1] += count; // pointer accumulated from all thread
136 }
137 data_.resize(rptr_.back());
138 }
139 }
140
149 void Push(std::size_t key, ValueType&& value, int threadid) {
150 size_t offset_key = is_row_major ? (key - base_row_offset_ - threadid * thread_displacement_)
151 : (key - base_row_offset_);
152 SizeType &rp = thread_rptr_[threadid][offset_key];
153 data_[rp++] = std::move(value);
154 }
155
156 private:
158 std::vector<SizeType> &rptr_;
160 std::vector<ValueType> &data_;
162 std::vector<std::vector<SizeType> > thread_rptr_;
164 size_t base_row_offset_;
166 size_t thread_displacement_;
167 };
168 } // namespace common
169 } // namespace xgboost
170 #endif // XGBOOST_COMMON_GROUP_DATA_H_
base.h
defines configuration macros of xgboost.
xgboost::common::ParallelGroupBuilder
multi-thread version of group builder
Definition: group_data.h:33
xgboost::common::ParallelGroupBuilder::InitBudget
void InitBudget(std::size_t max_key, int nthread)
step 1: initialize the helper, with hint of number keys and thread used in the construction
Definition: group_data.h:59
xgboost::common::ParallelGroupBuilder::AddBudget
void AddBudget(std::size_t key, int threadid, SizeType nelem=1)
step 2: add budget to each key
Definition: group_data.h:78
xgboost::common::ParallelGroupBuilder::Push
void Push(std::size_t key, ValueType &&value, int threadid)
step 4: add data to the allocated space, the calls to this function should be exactly match previous ...
Definition: group_data.h:149
xgboost::common::ParallelGroupBuilder::InitStorage
void InitStorage()
step 3: initialize the necessary storage
Definition: group_data.h:89
xgboost::common::ParallelGroupBuilder::ParallelGroupBuilder
ParallelGroupBuilder(std::vector< SizeType > *p_rptr, std::vector< ValueType > *p_data, size_t base_row_offset=0)
parallel group builder of data.
Definition: group_data.h:45
xgboost
namespace of xgboost
Definition: base.h:110