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stack_alloc.hpp
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1 #ifndef STAN_MATH_MEMORY_STACK_ALLOC_HPP
2 #define STAN_MATH_MEMORY_STACK_ALLOC_HPP
3
4 // TODO(Bob): <cstddef> replaces this ifdef in C++11, until then this
5 // is best we can do to get safe pointer casts to uints.
6 #if defined(_MSC_VER)
7 #include <msinttypes.h> // Microsoft Visual Studio lacks full stdint.h
8 #else
9 #include <stdint.h>
10 #endif
11 #include <stan/math/prim/scal/meta/likely.hpp>
12 #include <cstdlib>
13 #include <cstddef>
14 #include <sstream>
15 #include <stdexcept>
16 #include <vector>
17
18 namespace stan {
19
20 namespace math {
21
33 template <typename T>
34 bool is_aligned(T* ptr, unsigned int bytes_aligned) {
35 return (reinterpret_cast<uintptr_t>(ptr) % bytes_aligned) == 0U;
36 }
37
38
39 namespace {
40 const size_t DEFAULT_INITIAL_NBYTES = 1 << 16; // 64KB
41
42
43 // FIXME: enforce alignment
44 // big fun to inline, but only called twice
45 inline char* eight_byte_aligned_malloc(size_t size) {
46 char* ptr = static_cast<char*>(malloc(size));
47 if (!ptr) return ptr; // malloc failed to alloc
48 if (!is_aligned(ptr, 8U)) {
49 std::stringstream s;
50 s << "invalid alignment to 8 bytes, ptr="
51 << reinterpret_cast<uintptr_t>(ptr)
52 << std::endl;
53 throw std::runtime_error(s.str());
54 }
55 return ptr;
56 }
57 }
58
78 class stack_alloc {
79 private:
80 std::vector<char*> blocks_; // storage for blocks,
81 // may be bigger than cur_block_
82 std::vector<size_t> sizes_; // could store initial & shift for others
83 size_t cur_block_; // index into blocks_ for next alloc
84 char* cur_block_end_; // ptr to cur_block_ptr_ + sizes_[cur_block_]
85 char* next_loc_; // ptr to next available spot in cur
86 // block
87 // next three for keeping track of nested allocations on top of stack:
88 std::vector<size_t> nested_cur_blocks_;
89 std::vector<char*> nested_next_locs_;
90 std::vector<char*> nested_cur_block_ends_;
91
92
101 char* move_to_next_block(size_t len) {
102 char* result;
103 ++cur_block_;
104 // Find the next block (if any) containing at least len bytes.
105 while ((cur_block_ < blocks_.size()) && (sizes_[cur_block_] < len))
106 ++cur_block_;
107 // Allocate a new block if necessary.
108 if (unlikely(cur_block_ >= blocks_.size())) {
109 // New block should be max(2*size of last block, len) bytes.
110 size_t newsize = sizes_.back() * 2;
111 if (newsize < len)
112 newsize = len;
113 blocks_.push_back(eight_byte_aligned_malloc(newsize));
114 if (!blocks_.back())
115 throw std::bad_alloc();
116 sizes_.push_back(newsize);
117 }
118 result = blocks_[cur_block_];
119 // Get the object's state back in order.
120 next_loc_ = result + len;
121 cur_block_end_ = result + sizes_[cur_block_];
122 return result;
123 }
124
125 public:
135 explicit stack_alloc(size_t initial_nbytes = DEFAULT_INITIAL_NBYTES) :
136 blocks_(1, eight_byte_aligned_malloc(initial_nbytes)),
137 sizes_(1, initial_nbytes),
138 cur_block_(0),
139 cur_block_end_(blocks_[0] + initial_nbytes),
140 next_loc_(blocks_[0]) {
141 if (!blocks_[0])
142 throw std::bad_alloc(); // no msg allowed in bad_alloc ctor
143 }
144
151 ~stack_alloc() {
152 // free ALL blocks
153 for (size_t i = 0; i < blocks_.size(); ++i)
154 if (blocks_[i])
155 free(blocks_[i]);
156 }
157
170 inline void* alloc(size_t len) {
171 // Typically, just return and increment the next location.
172 char* result = next_loc_;
173 next_loc_ += len;
174 // Occasionally, we have to switch blocks.
175 if (unlikely(next_loc_ >= cur_block_end_))
176 result = move_to_next_block(len);
177 return reinterpret_cast<void*>(result);
178 }
179
188 template <typename T>
189 inline
190 T* alloc_array(size_t n) {
191 return static_cast<T*>(alloc(n * sizeof(T)));
192 }
193
194
201 inline void recover_all() {
202 cur_block_ = 0;
203 next_loc_ = blocks_[0];
204 cur_block_end_ = next_loc_ + sizes_[0];
205 }
206
211 inline void start_nested() {
212 nested_cur_blocks_.push_back(cur_block_);
213 nested_next_locs_.push_back(next_loc_);
214 nested_cur_block_ends_.push_back(cur_block_end_);
215 }
216
220 inline void recover_nested() {
221 if (unlikely(nested_cur_blocks_.empty()))
222 recover_all();
223
224 cur_block_ = nested_cur_blocks_.back();
225 nested_cur_blocks_.pop_back();
226
227 next_loc_ = nested_next_locs_.back();
228 nested_next_locs_.pop_back();
229
230 cur_block_end_ = nested_cur_block_ends_.back();
231 nested_cur_block_ends_.pop_back();
232 }
233
239 inline void free_all() {
240 // frees all BUT the first (index 0) block
241 for (size_t i = 1; i < blocks_.size(); ++i)
242 if (blocks_[i])
243 free(blocks_[i]);
244 sizes_.resize(1);
245 blocks_.resize(1);
246 recover_all();
247 }
248
259 size_t bytes_allocated() {
260 size_t sum = 0;
261 for (size_t i = 0; i <= cur_block_; ++i) {
262 sum += sizes_[i];
263 }
264 return sum;
265 }
266 };
267
268 }
269 }
270 #endif
stan::math::sum
fvar< T > sum(const std::vector< fvar< T > > &m)
Return the sum of the entries of the specified standard vector.
Definition: sum.hpp:20
stan::math::stack_alloc::~stack_alloc
~stack_alloc()
Destroy this memory allocator.
Definition: stack_alloc.hpp:151
stan::math::stack_alloc::recover_nested
void recover_nested()
recover memory back to the last start_nested call.
Definition: stack_alloc.hpp:220
stan::math::stack_alloc::free_all
void free_all()
Free all memory used by the stack allocator other than the initial block allocation back to the syste...
Definition: stack_alloc.hpp:239
stan::math::stack_alloc::recover_all
void recover_all()
Recover all the memory used by the stack allocator.
Definition: stack_alloc.hpp:201
unlikely
#define unlikely(x)
Definition: likely.hpp:9
stan::math::stack_alloc::bytes_allocated
size_t bytes_allocated()
Return number of bytes allocated to this instance by the heap.
Definition: stack_alloc.hpp:259
likely.hpp
stan::math::stack_alloc::alloc_array
T * alloc_array(size_t n)
Allocate an array on the arena of the specified size to hold values of the specified template paramet...
Definition: stack_alloc.hpp:190
stan::math::size
int size(const std::vector< T > &x)
Definition: size.hpp:11
stan::math::stack_alloc::start_nested
void start_nested()
Store current positions before doing nested operation so can recover back to start.
Definition: stack_alloc.hpp:211
stan::math::is_aligned
bool is_aligned(T *ptr, unsigned int bytes_aligned)
Return true if the specified pointer is aligned on the number of bytes.
Definition: stack_alloc.hpp:34
stan::math::stack_alloc::stack_alloc
stack_alloc(size_t initial_nbytes=DEFAULT_INITIAL_NBYTES)
Construct a resizable stack allocator initially holding the specified number of bytes.
Definition: stack_alloc.hpp:135
stan::math::stack_alloc
An instance of this class provides a memory pool through which blocks of raw memory may be allocated ...
Definition: stack_alloc.hpp:78
stan::math::stack_alloc::alloc
void * alloc(size_t len)
Return a newly allocated block of memory of the appropriate size managed by the stack allocator...
Definition: stack_alloc.hpp:170

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