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Reference Guide
StackAllocator.h
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1// @(#)root/minuit2:$Id$
2// Authors: M. Winkler, F. James, L. Moneta, A. Zsenei 2003-2005
3
4/**********************************************************************
5 * *
6 * Copyright (c) 2005 LCG ROOT Math team, CERN/PH-SFT *
7 * *
8 **********************************************************************/
9
10#ifndef ROOT_Minuit2_StackAllocator
11#define ROOT_Minuit2_StackAllocator
12
13#include "Minuit2/MnConfig.h"
14
15// comment out this line and recompile if you want to gain additional
16// performance (the gain is mainly for "simple" functions which are easy
17// to calculate and vanishes quickly if going to cost-intensive functions)
18// the library is no longer thread save however
19
20#ifdef MN_USE_STACK_ALLOC
21#define _MN_NO_THREAD_SAVE_
22#endif
23
24//#include <iostream>
25
26
27
28#include <cstdlib>
29#include <new>
30
31namespace ROOT {
32
33 namespace Minuit2 {
34
35
36
37/// define stack allocator symbol
38
39
40
42class StackError {};
43// using namespace std;
44
45/** StackAllocator controls the memory allocation/deallocation of Minuit. If
46 _MN_NO_THREAD_SAVE_ is defined, memory is taken from a pre-allocated piece
47 of heap memory which is then used like a stack, otherwise via standard
48 malloc/free. Note that defining _MN_NO_THREAD_SAVE_ makes the code thread-
49 unsave. The gain in performance is mainly for cost-cheap FCN functions.
50 */
51
53
54public:
55
56// enum {default_size = 1048576};
57 enum {default_size = 524288};
58
60#ifdef _MN_NO_THREAD_SAVE_
61 //std::cout<<"StackAllocator Allocate "<<default_size<<std::endl;
62 fStack = new unsigned char[default_size];
63#endif
64 fStackOffset = 0;
65 fBlockCount = 0;
66 }
67
69#ifdef _MN_NO_THREAD_SAVE_
70 //std::cout<<"StackAllocator destruct "<<fStackOffset<<std::endl;
71 if(fStack) delete [] fStack;
72#endif
73 }
74
75 void* Allocate( size_t nBytes) {
76#ifdef _MN_NO_THREAD_SAVE_
77 if(fStack == 0) fStack = new unsigned char[default_size];
78 int nAlloc = AlignedSize(nBytes);
79 CheckOverflow(nAlloc);
80
81// std::cout << "Allocating " << nAlloc << " bytes, requested = " << nBytes << std::endl;
82
83 // write the start position of the next block at the start of the block
85 // write the start position of the new block at the end of the block
86 WriteInt( fStackOffset + nAlloc - sizeof(int), fStackOffset);
87
88 void* result = fStack + fStackOffset + sizeof(int);
89 fStackOffset += nAlloc;
91
92#ifdef DEBUG_ALLOCATOR
94#endif
95
96#else
97 void* result = malloc(nBytes);
98 if (!result) throw std::bad_alloc();
99#endif
100
101 return result;
102 }
103
104 void Deallocate( void* p) {
105#ifdef _MN_NO_THREAD_SAVE_
106 // int previousOffset = ReadInt( fStackOffset - sizeof(int));
107 int delBlock = ToInt(p);
108 int nextBlock = ReadInt( delBlock);
109 int previousBlock = ReadInt( nextBlock - sizeof(int));
110 if ( nextBlock == fStackOffset) {
111 // deallocating last allocated
112 fStackOffset = previousBlock;
113 }
114 else {
115 // overwrite previous adr of next block
116 int nextNextBlock = ReadInt(nextBlock);
117 WriteInt( nextNextBlock - sizeof(int), previousBlock);
118 // overwrite head of deleted block
119 WriteInt( previousBlock, nextNextBlock);
120 }
121 fBlockCount--;
122
123#ifdef DEBUG_ALLOCATOR
125#endif
126#else
127 free(p);
128#endif
129 // std::cout << "Block at " << delBlock
130 // << " deallocated, fStackOffset = " << fStackOffset << std::endl;
131 }
132
133 int ReadInt( int offset) {
134 int* ip = (int*)(fStack+offset);
135
136 // std::cout << "read " << *ip << " from offset " << offset << std::endl;
137
138 return *ip;
139 }
140
141 void WriteInt( int offset, int Value) {
142
143 // std::cout << "writing " << Value << " to offset " << offset << std::endl;
144
145 int* ip = reinterpret_cast<int*>(fStack+offset);
146 *ip = Value;
147 }
148
149 int ToInt( void* p) {
150 unsigned char* pc = static_cast<unsigned char*>(p);
151
152 // std::cout << "toInt: p = " << p << " fStack = " << (void*) fStack << std::endl;
153 // VC 7.1 warning:conversin from __w64 int to int
154 int userBlock = pc - fStack;
155 return userBlock - sizeof(int); // correct for starting int
156 }
157
158 int AlignedSize( int nBytes) {
159 const int fAlignment = 4;
160 int needed = nBytes % fAlignment == 0 ? nBytes : (nBytes/fAlignment+1)*fAlignment;
161 return needed + 2*sizeof(int);
162 }
163
164 void CheckOverflow( int n) {
165 if (fStackOffset + n >= default_size) {
166 //std::cout << " no more space on stack allocator" << std::endl;
167 throw StackOverflow();
168 }
169 }
170
172
173 //std::cout << "checking consistency for " << fBlockCount << " blocks"<< std::endl;
174
175 // loop over all blocks
176 int beg = 0;
177 int end = fStackOffset;
178 int nblocks = 0;
179 while (beg < fStackOffset) {
180 end = ReadInt( beg);
181
182 // std::cout << "beg = " << beg << " end = " << end
183 // << " fStackOffset = " << fStackOffset << std::endl;
184
185 int beg2 = ReadInt( end - sizeof(int));
186 if ( beg != beg2) {
187 //std::cout << " beg != beg2 " << std::endl;
188 return false;
189 }
190 nblocks++;
191 beg = end;
192 }
193 if (end != fStackOffset) {
194 //std::cout << " end != fStackOffset" << std::endl;
195 return false;
196 }
197 if (nblocks != fBlockCount) {
198 //std::cout << "nblocks != fBlockCount" << std::endl;
199 return false;
200 }
201 //std::cout << "Allocator is in consistent state, nblocks = " << nblocks << std::endl;
202 return true;
203 }
204
205private:
206
207 unsigned char* fStack;
208// unsigned char fStack[default_size];
211
212};
213
214
215
217
218 // t.b.d need to use same trick as Boost singleton.hpp to be sure that
219 // StackAllocator is created before main()
220
221 public:
222
223
224 static StackAllocator & Get() {
225 static StackAllocator gStackAllocator;
226 return gStackAllocator;
227 }
228};
229
230
231
232 } // namespace Minuit2
233
234} // namespace ROOT
235
236#endif
#define free
Definition: civetweb.c:1539
#define malloc
Definition: civetweb.c:1536
static StackAllocator & Get()
StackAllocator controls the memory allocation/deallocation of Minuit.
void WriteInt(int offset, int Value)
void * Allocate(size_t nBytes)
define stack allocator symbol
const Int_t n
Definition: legend1.C:16
VSD Structures.
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static constexpr double pc
const char * Value
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