我在MPI中编写了一个简单的程序,它在处理器之间发送和接收消息,但运行时出现分段错误。
这是我的整个代码
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <string>
#include <string.h>
#include <strings.h>
#include <sstream>
#include<mpi.h>
using namespace std;
class Case {
public:
int value;
std::stringstream sta;
};
int main(int argc, char **argv) {
int rank,size;
MPI::Init(argc,argv);
rank=MPI::COMM_WORLD.Get_rank();
size=MPI::COMM_WORLD.Get_size();
if(rank==0){
Case *s=new Case();
s->value=1;
s->sta<<"test";
cout<<"\nInside send before copy value :"<<s->value;
fflush(stdout);
cout<<"\nInside send before copy data :"<<s->sta.str();
fflush(stdout);
Case scpy;
scpy.value=s->value;
scpy.sta<<(s->sta).rdbuf();
cout<<"\nInside send after copy value :"<<scpy.value;
cout<<"\nInside send after copy value :"<<scpy.sta.str();
MPI::COMM_WORLD.Send(&scpy,sizeof(Case),MPI::BYTE,1,23);
}
MPI::COMM_WORLD.Barrier();
if(rank==1){
Case r;
MPI::COMM_WORLD.Recv(&r,sizeof(Case),MPI::BYTE,0,23);
cout<<"\nRecieve value"<<r.value;
fflush(stdout);
cout<<"\nRecieve data"<<r.sta;
fflush(stdout);
}
MPI::Finalize();
return 0;
}
我收到以下错误消息,我无法弄清楚这个程序有什么问题。
有人可以解释一下吗?
Inside send before copy value :1
Inside send before copy data :test
Inside send after copy value :1
Recieve value1
Recieve data0xbfa5d6b4[localhost:03706] *** Process received signal ***
[localhost:03706] Signal: Segmentation fault (11)
[localhost:03706] Signal code: Address not mapped (1)
[localhost:03706] Failing at address: 0x8e1a210
[localhost:03706] [ 0] [0xe6940c]
[localhost:03706] [ 1] /usr/lib/libstdc++.so.6(_ZNSt18basic_stringstreamIcSt11char_traitsIcESaIcEED1Ev+0xc6) [0x6a425f6]
[localhost:03706] [ 2] ./a.out(_ZN4CaseD1Ev+0x14) [0x8052d8e]
[localhost:03706] [ 3] ./a.out(main+0x2f9) [0x804f90d]
[localhost:03706] [ 4] /lib/libc.so.6(__libc_start_main+0xe6) [0x897e36]
[localhost:03706] [ 5] ./a.out() [0x804f581]
[localhost:03706] *** End of error message ***
--------------------------------------------------------------------------
mpirun noticed that process rank 1 with PID 3706 on node localhost.localdomain exited on signal 11 (Segmentation fault).
--------------------------------------------------------------------------
答案 0 :(得分:3)
我认为问题在于:
MPI::COMM_WORLD.Send(&scpy,sizeof(Case),MPI::BYTE,1,23);
将一个Case结构的副本发送给接收者,但它发送的字节的原始副本并不是很有用。 std :: stringstream类将包含指向用于存储字符串的实际内存的指针,因此此代码将:
接收器在尝试取消引用无效指针时会发出错误。
解决此问题的一种方法是自己发送角色数据。
在这种方法中,您将发送一条指向std :: stringstream :: str():: c_str()且长度为std :: stringstream :: str():: size()* sizeof(char)的消息。
一种替代方法似乎更适合您尝试使用MPI和字符串的方式是使用Boost库。 Boost包含MPI函数,可以自动为您序列化数据。
有关Boost和MPI的有用教程on the boost website。 以下是该教程中执行类似任务的示例代码:
#include <boost/mpi.hpp>
#include <iostream>
#include <string>
#include <boost/serialization/string.hpp>
namespace mpi = boost::mpi;
int main(int argc, char* argv[])
{
mpi::environment env(argc, argv);
mpi::communicator world;
if (world.rank() == 0) {
world.send(1, 0, std::string("Hello"));
std::string msg;
world.recv(1, 1, msg);
std::cout << msg << "!" << std::endl;
} else {
std::string msg;
world.recv(0, 0, msg);
std::cout << msg << ", ";
std::cout.flush();
world.send(0, 1, std::string("world"));
}
return 0;
}