MPI_send和MPI_receive字符串
MPI_send and MPI_receive string
我读了很多页,但我找不到解决问题的方法:我必须将一个由3个整数组成的数组从根进程传递到工作进程,其中:
- 第一个int是每个进程要验证的页数
- 第二个int是开始验证的id
- 第三个int是要在这些页面中搜索的字符串的长度
在发送这个数组之后,我发送要搜索的字符串。问题出在接收上:发送的字符串的长度是正确的,但当我输出字符串时,我会这样做:例如,如果我发送"sport",那么输出时我会有"sport222|||"。这是代码:
int main(int argc, char *argv[]){
int rank;
int noOfProcs;
string stringToBeSearched = "";
int root_process;
int ierr;
int avgPerProcess;
int totalNoOfPages;
int noOfPagesForLastProc;
int proc;
char* receivedString = "";
int receivedSLen;
int dataToSend[3];
int receivedData[3];
vector<HtmlPage> pages;
char* s = "";
clock_t tStart;
MPI_Status status;
ierr = MPI_Init(&argc, &argv);
root_process = 0;
ierr = MPI_Comm_rank(MPI_COMM_WORLD, &rank);
ierr = MPI_Comm_size(MPI_COMM_WORLD, &noOfProcs);
if (rank == root_process) {
cout << "Enter text: ";
getline(cin, stringToBeSearched);
//calculate the number of pages to be verified by each process
totalNoOfPages = getTotalNumberOfPages();
avgPerProcess = totalNoOfPages / noOfProcs;
//send the array to each process
noOfPagesForLastProc = avgPerProcess + (totalNoOfPages % noOfProcs);
for (proc = 1; proc < noOfProcs; proc++) {
dataToSend[0] = avgPerProcess;
dataToSend[1] = proc * avgPerProcess;
dataToSend[2] = stringToBeSearched.size();
if (proc == noOfProcs - 1){
dataToSend[0] = noOfPagesForLastProc;
}
ierr = MPI_Send(&dataToSend[0], 3, MPI_INT,
proc, send_data_tag, MPI_COMM_WORLD);
//send the string to be searched
ierr = MPI_Send(stringToBeSearched.c_str(), stringToBeSearched.size(), MPI_CHAR, proc, send_data_tag, MPI_COMM_WORLD);
}
//verify pages in the segment assigned
//to the root process
//get the pages assigned
pages = getPagesForProcess(avgPerProcess, 0);
for (int i = 0; i < pages.size(); i++) {
string searched = pages[i].getContent();
const char* ch = searched.c_str();
if (strstr(ch, s) != NULL){
cout << "Process 0" << " founded matches at: " << endl;
cout << pages[i].getUrl() << endl;
}
}
}
else {
//worker process receive the array segment,
//storing it in a "local" array
ierr = MPI_Recv(&receivedData[0], 3, MPI_INT,
root_process, send_data_tag, MPI_COMM_WORLD, &status);
receivedSLen = receivedData[2];
receivedString = new char[receivedSLen];
ierr = MPI_Recv(receivedString, receivedSLen, MPI_CHAR, root_process, send_data_tag, MPI_COMM_WORLD, &status);
//this line of code outputs the "bad" string
cout << "received string = " << receivedString << endl;
//get the assigned pages to verify
pages = getPagesForProcess(receivedData[0], receivedData[1]);
for (int i = 0; i < pages.size(); i++) {
string searched = pages[i].getContent();
const char* ch = searched.c_str();
if (strstr(ch, receivedString) != NULL){
cout << "Process " << rank << " founded matches at: " << endl;
cout << pages[i].getUrl() << endl;
}
else {
cout << "No matches founded by process " << rank << endl;
}
}
}
cout << "Time taken for execution " << (double)(clock() - tStart) / CLOCKS_PER_SEC << " s." << endl;
ierr = MPI_Finalize();
_getch();
return 0;
}
问题是您的字符串缺少null终止符。
receivedString = new char[receivedSLen];
应为:
receivedString = new char[receivedSLen + 1]();
这会为终止的null多分配1个字符,并将数据初始化为默认值(无论如何都是0)。
更好的是,使用std::vector
消除内存泄漏
std::vector<char> receivedString(receivedSLen + 1,0);
cout << "received string = " << &receivedString[0] << endl;
您应该考虑的问题是字符串是否可以包含嵌入的NULL
字符。如果是这样,那么您必须使用不同的方法来处理字符串,因为您现在使用的函数依赖于终止的