[已解决]c预定义问题

lqhenwunai

请教各位大神，

我在读别人代码时遇到以下预定义语句，其中v是一个结构体变量，包含val,sum,sum2 这三个real类型数据，n是int型参数

before:

1. 
   
2. #define PropAvg(v, n) \
   
3.    v.sum /= n, v.sum2 = sqrt (Max (v.sum2 / n - Sqr (v.sum), 0.))
   

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即PropAvg这个函数把v的sum2运算后返还给v的sum2


但是当我对相关变量进行打印时（check 那行语句），即显示打印v.sum2, 以及 v.sum2等号右面内容，得到的结果却不同

1. 
   
2. #define PropAvg(v, n) \
   
3.    v.sum /= n, v.sum2 = sqrt (Max (v.sum2 / n - Sqr (v.sum), 0.));\
   
4.   printf("Check if same  %f %f \n",      v.sum2,       sqrt (Max (v.sum2 / n - Sqr (v.sum), 0.)));\
   
5. 
   

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得到的结果是：
Check if same 0.146077 0.000000

请问这是什么原因呢？

最佳答案

月排行榜 / 总排行榜

人造人

2022-9-21 00:58:50

今天有点晚了，明天给你看看

跳转到最佳答案楼层

人造人

发完整的代码，你不发完整的代码我们就没办法给你调试代码

lqhenwunai

人造人 发表于 2022-9-19 15:27
发完整的代码，你不发完整的代码我们就没办法给你调试代码

谢谢。
有好几个文件构成，所以请直接下载吧：
链接: https://pan.baidu.com/s/13h7lZvPcbc55j_KTREfsEw?pwd=p8wx 提取码: p8wx

相关预定义文件在src/in_mddefs.h文件中。

编译运行的话，直接./crun.sh

lqhenwunai

人造人 发表于 2022-9-19 15:27
发完整的代码，你不发完整的代码我们就没办法给你调试代码

谢谢。
文件比较多，请直接下载吧。

提取码4tdw


上面提到的预定义的文件在src/in_mddefs.h中

加压后直接运行./crun.sh

会得到类似这样的输出
usage ./crun.sh chp# hw#. i.e. ./crun.sh 02 1
NameList -- data
deltaT                0.00500000
density                0.800000
initUcell        20 20
stepAvg                100
stepEquil        0
stepLimit        10000
temperature        1.00000
----
lqtest  1 sum sum2 1.106495 1.224331   
lqtest  2 sum sum2 2.383097 2.854043   
lqtest  3 sum sum2 3.859806 5.034715   
lqtest  4 sum sum2 5.563714 7.938016   
lqtest  5 sum sum2 7.522566 11.775116   
lqtest  6 sum sum2 9.763801 16.798253   

....
----------------------
Check if same 0.000059 0.000000
------------------------
----------------------
Check if same 0.016839 0.000000
------------------------

（跑一两秒结束循环就好。）

人造人

今天有点晚了，明天给你看看

lqhenwunai

人造人 发表于 2022-9-21 00:58
今天有点晚了，明天给你看看

哦，非常感谢。不过已经查出问题在哪了。不用浪费时间了。实在不好意思。

人造人

lqhenwunai 发表于 2022-9-21 20:41
哦，非常感谢。不过已经查出问题在哪了。不用浪费时间了。实在不好意思。

结果确实是0，没问题
把代码改成这样，然后你看我的调试过程

1.     //PropAvg (totEnergy, stepAvg);
   
2. 
   
3.      /*
   
4.     totEnergy.sum /= stepAvg;
   
5.     totEnergy.sum2 = sqrt (Max (totEnergy.sum2 / stepAvg - Sqr (totEnergy.sum), 0.));
   
6.     printf("Check if same%f %f \n",totEnergy.sum2,sqrt (Max (totEnergy.sum2 / stepAvg - Sqr (totEnergy.sum), 0.)));
   
7.     */
   
8.     totEnergy.sum /= stepAvg;
   
9.     //totEnergy.sum2 = sqrt (Max (totEnergy.sum2 / stepAvg - Sqr (totEnergy.sum), 0.));
   
10.     {
    
11.         double a = Sqr(totEnergy.sum);
    
12.         double b = totEnergy.sum2 / stepAvg;
    
13.         double c = b - a;
    
14.         double d = Max(c, 0);
    
15.         totEnergy.sum2 = sqrt(d);
    
16.     }
    
17.     //printf("Check if same%f %f \n",totEnergy.sum2,sqrt (Max (totEnergy.sum2 / stepAvg - Sqr (totEnergy.sum), 0.)));
    
18.     {
    
19.         double a = Sqr(totEnergy.sum);
    
20.         double b = totEnergy.sum2 / stepAvg;
    
21.         double c = b - a;
    
22.         double d = Max(c, 0);
    
23.         double e = sqrt(d);
    
24.         printf("Check if same%f %f \n", totEnergy.sum2, e);
    
25.     }
    
26. 
    
27. 
    
28. 
    
29.     PropAvg (kinEnergy, stepAvg);
    
30. //  printf("~~~~~~~~~~~~~~~~~~~~~~~~~~\n");
    
31. //  printf("before %f %f\n",PropEst(pressure));
    

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1. PropEst  100 sum sum2 457.510422 2166.029826
   
2. 
   
3. Breakpoint 1, AccumProps (icode=2) at src/pr_02_1.c:323
   
4. 323            totEnergy.sum /= stepAvg;
   
5. (gdb) display totEnergy
   
6. 1: totEnergy = {val = 0.99522634417443578, sum = 99.518657934111843, sum2 = 99.039636125322588}
   
7. (gdb) display stepAvg
   
8. 2: stepAvg = 100
   
9. (gdb) n
   
10. 326                double a = Sqr(totEnergy.sum);
    
11. 1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 99.039636125322588}
    
12. 2: stepAvg = 100
    
13. (gdb) n
    
14. 327                double b = totEnergy.sum2 / stepAvg;
    
15. 1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 99.039636125322588}
    
16. 2: stepAvg = 100
    
17. (gdb) print a
    
18. $1 = 0.9903963277006762
    
19. (gdb) n
    
20. 328                double c = b - a;
    
21. 1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 99.039636125322588}
    
22. 2: stepAvg = 100
    
23. (gdb) print b
    
24. $2 = 0.99039636125322583
    
25. (gdb) n
    
26. 329                double d = Max(c, 0);
    
27. 1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 99.039636125322588}
    
28. 2: stepAvg = 100
    
29. (gdb) print c
    
30. $3 = 3.3552549627557937e-08
    
31. (gdb) n
    
32. 330                totEnergy.sum2 = sqrt(d);
    
33. 1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 99.039636125322588}
    
34. 2: stepAvg = 100
    
35. (gdb) print d
    
36. $4 = 3.3552549627557937e-08
    
37. (gdb) n
    
38. 334                double a = Sqr(totEnergy.sum);
    
39. 1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 0.00018317355056764593}
    
40. 2: stepAvg = 100
    
41. (gdb) n
    
42. 335                double b = totEnergy.sum2 / stepAvg;
    
43. 1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 0.00018317355056764593}
    
44. 2: stepAvg = 100
    
45. (gdb) print a
    
46. $5 = 0.9903963277006762
    
47. (gdb) n
    
48. 336                double c = b - a;
    
49. 1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 0.00018317355056764593}
    
50. 2: stepAvg = 100
    
51. (gdb) print b
    
52. $6 = 1.8317355056764593e-06
    
53. (gdb) n
    
54. 337                double d = Max(c, 0);
    
55. 1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 0.00018317355056764593}
    
56. 2: stepAvg = 100
    
57. (gdb) print c
    
58. $7 = -0.99039449596517048
    
59. (gdb) n
    
60. 338                double e = sqrt(d);
    
61. 1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 0.00018317355056764593}
    
62. 2: stepAvg = 100
    
63. (gdb) print d
    
64. $8 = 0
    
65. (gdb) n
    
66. 339                printf("Check if same%f %f \n", totEnergy.sum2, e);
    
67. 1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 0.00018317355056764593}
    
68. 2: stepAvg = 100
    
69. (gdb) print e
    
70. $9 = 0
    
71. (gdb) n
    
72. Check if same0.000183 0.000000
    
73. 344            PropAvg (kinEnergy, stepAvg);
    
74. 1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 0.00018317355056764593}
    
75. 2: stepAvg = 100
    
76. (gdb)
    

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