[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:

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

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

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

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

    //PropAvg (totEnergy, stepAvg);

     /*
    totEnergy.sum /= stepAvg;
    totEnergy.sum2 = sqrt (Max (totEnergy.sum2 / stepAvg - Sqr (totEnergy.sum), 0.));
    printf("Check if same%f %f \n",totEnergy.sum2,sqrt (Max (totEnergy.sum2 / stepAvg - Sqr (totEnergy.sum), 0.)));
    */
    totEnergy.sum /= stepAvg;
    //totEnergy.sum2 = sqrt (Max (totEnergy.sum2 / stepAvg - Sqr (totEnergy.sum), 0.));
    {
        double a = Sqr(totEnergy.sum);
        double b = totEnergy.sum2 / stepAvg;
        double c = b - a;
        double d = Max(c, 0);
        totEnergy.sum2 = sqrt(d);
    }
    //printf("Check if same%f %f \n",totEnergy.sum2,sqrt (Max (totEnergy.sum2 / stepAvg - Sqr (totEnergy.sum), 0.)));
    {
        double a = Sqr(totEnergy.sum);
        double b = totEnergy.sum2 / stepAvg;
        double c = b - a;
        double d = Max(c, 0);
        double e = sqrt(d);
        printf("Check if same%f %f \n", totEnergy.sum2, e);
    }



    PropAvg (kinEnergy, stepAvg);
//  printf("~~~~~~~~~~~~~~~~~~~~~~~~~~\n");
//  printf("before %f %f\n",PropEst(pressure));

 PropEst  100 sum sum2 457.510422 2166.029826

Breakpoint 1, AccumProps (icode=2) at src/pr_02_1.c:323
323            totEnergy.sum /= stepAvg;
(gdb) display totEnergy
1: totEnergy = {val = 0.99522634417443578, sum = 99.518657934111843, sum2 = 99.039636125322588}
(gdb) display stepAvg
2: stepAvg = 100
(gdb) n
326                double a = Sqr(totEnergy.sum);
1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 99.039636125322588}
2: stepAvg = 100
(gdb) n
327                double b = totEnergy.sum2 / stepAvg;
1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 99.039636125322588}
2: stepAvg = 100
(gdb) print a
$1 = 0.9903963277006762
(gdb) n
328                double c = b - a;
1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 99.039636125322588}
2: stepAvg = 100
(gdb) print b
$2 = 0.99039636125322583
(gdb) n
329                double d = Max(c, 0);
1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 99.039636125322588}
2: stepAvg = 100
(gdb) print c
$3 = 3.3552549627557937e-08
(gdb) n
330                totEnergy.sum2 = sqrt(d);
1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 99.039636125322588}
2: stepAvg = 100
(gdb) print d
$4 = 3.3552549627557937e-08
(gdb) n
334                double a = Sqr(totEnergy.sum);
1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 0.00018317355056764593}
2: stepAvg = 100
(gdb) n
335                double b = totEnergy.sum2 / stepAvg;
1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 0.00018317355056764593}
2: stepAvg = 100
(gdb) print a
$5 = 0.9903963277006762
(gdb) n
336                double c = b - a;
1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 0.00018317355056764593}
2: stepAvg = 100
(gdb) print b
$6 = 1.8317355056764593e-06
(gdb) n
337                double d = Max(c, 0);
1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 0.00018317355056764593}
2: stepAvg = 100
(gdb) print c
$7 = -0.99039449596517048
(gdb) n
338                double e = sqrt(d);
1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 0.00018317355056764593}
2: stepAvg = 100
(gdb) print d
$8 = 0
(gdb) n
339                printf("Check if same%f %f \n", totEnergy.sum2, e);
1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 0.00018317355056764593}
2: stepAvg = 100
(gdb) print e
$9 = 0
(gdb) n
 Check if same0.000183 0.000000
344            PropAvg (kinEnergy, stepAvg);
1: totEnergy = {val = 0.99522634417443578, sum = 0.99518657934111843, sum2 = 0.00018317355056764593}
2: stepAvg = 100
(gdb)