空间开销模型源码-白红宇

空间开销模型源码

阅读量：5884 次

发布时间：2019-06-19

本文共 3703 字，大约阅读时间需要 12 分钟。

此源码参考编程珠玑附录C时空开销源码例一。改动在于用template代替Macro。

Measure 方法：连续new类型T十二次，查看系统为每一个对象分配的实际大小。

结论：在64位的机器上，如果类型大小小于等于4字节，则分配64字节的空间。如果类型大小大于4字节，则最低分配72字节，以后每多出8字节，就分配多8字节。

#include "stdafx.h"#include 
     
      using namespace std;template 
      
       void MEASURE() {                        cout << typeid(T).name() << "\t";                        cout << sizeof(T) << "\t";                    int lastp = 0;                            for (int i = 0; i < 11; i++) {                            T *p = new T;                            int thisp = (int) p;                        if (lastp != 0)                                cout << " " << thisp - lastp;                    lastp = thisp;                        }                                cout << "\n";                        }template 
       
        struct structii { char c[i]; };int main(){    cout << "Raw sizeof";    cout << "\nsizeof(char)="     << sizeof(char);        cout << "  sizeof(short)="    << sizeof(short);    cout << "  sizeof(int)="      << sizeof(int);    cout << "\nsizeof(float)="    << sizeof(float);    cout << "  sizeof(struct *)=" << sizeof(structii<1> *);    cout << "  sizeof(long)="     << sizeof(long);    cout << "\nsizeof(double)="   << sizeof(double);    cout << "\n\nMEASURE\n";    MEASURE
        
         <1>>();    MEASURE
         
          <2>>();    MEASURE
          
           <3>>(); MEASURE
           
            <4>>(); MEASURE
            
             <5>>(); MEASURE
             
              <6>>(); MEASURE
              
               <7>>(); MEASURE
               
                <8>>(); MEASURE
                
                 <9>>(); MEASURE
                 
                  <10>>(); MEASURE
                  
                   <11>>(); MEASURE
                   
                    <12>>(); MEASURE
                    
                     <13>>(); MEASURE
                     
                      <14>>(); MEASURE
                      
                       <15>>(); MEASURE
                       
                        <16>>(); MEASURE
                        
                         <17>>(); MEASURE
                         
                          <18>>(); MEASURE
                          
                           <19>>(); MEASURE
                           
                            <20>>(); MEASURE
                            
                             <21>>(); MEASURE
                             
                              <22>>(); MEASURE
                              
                               <23>>(); MEASURE
                               
                                <24>>(); MEASURE
                                
                                 <25>>(); MEASURE
                                 
                                  <26>>(); MEASURE
                                  
                                   <27>>(); return 0;}

Output on my machine：x64

Raw sizeofsizeof(char)=1  sizeof(short)=2  sizeof(int)=4sizeof(float)=4  sizeof(struct *)=4  sizeof(long)=4sizeof(double)=8MEASUREstruct structii<1>      1        12904 -9184 9616 64 64 64 368 64 64 64struct structii<2>      2        64 64 64 64 64 64 64 64 64 64struct structii<3>      3        64 64 64 64 64 64 64 64 64 64struct structii<4>      4        64 64 64 64 64 64 64 64 64 64struct structii<5>      5        72 72 72 72 72 72 72 72 72 72struct structii<6>      6        72 72 72 72 72 72 72 72 72 72struct structii<7>      7        72 72 72 72 72 72 72 72 72 72struct structii<8>      8        72 72 72 72 72 72 72 72 72 72struct structii<9>      9        72 72 72 72 72 72 72 72 72 72struct structii<10>     10       72 72 72 72 72 72 72 72 72 72struct structii<11>     11       72 72 72 72 72 72 72 72 72 72struct structii<12>     12       72 72 72 72 72 72 72 72 72 72struct structii<13>     13       80 80 80 80 80 80 80 80 80 80struct structii<14>     14       80 80 80 80 80 80 80 80 80 80struct structii<15>     15       80 80 80 80 80 80 80 80 80 80struct structii<16>     16       80 80 80 80 80 80 80 80 80 80struct structii<17>     17       80 80 80 80 80 80 80 80 80 80struct structii<18>     18       80 80 80 80 80 80 80 80 80 80struct structii<19>     19       80 80 80 80 80 80 80 80 80 80struct structii<20>     20       80 80 80 80 80 80 80 80 80 80struct structii<21>     21       88 88 88 88 88 88 88 88 88 88struct structii<22>     22       88 88 88 88 88 88 88 88 88 88struct structii<23>     23       88 88 88 88 88 88 88 88 88 88struct structii<24>     24       88 88 88 88 88 88 88 88 88 88struct structii<25>     25       88 88 88 88 88 88 88 88 88 88struct structii<26>     26       88 88 88 88 88 88 88 88 88 88struct structii<27>     27       88 88 88 88 88 88 88 88 88 88

转载于:https://www.cnblogs.com/liquadli/p/3611108.html

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