How to clearly kill a mpi program which is launched by Qprocess?

[SJ2050]

I have a pyqt program and there is a requirement to run an external mpi program. I use Qprocess to launch the mpi program. Howerer, I find when I call kill method to terminate the mpi programs, the mpi processes is still running. Do anyone know how to clearly kill the mpi grograms launched by Qprocess?

Below is my test program:

test.py

import sys
from PyQt5 import QtCore, QtWidgets
from PyQt5.QtCore import pyqtSignal, QThread, QProcess
from PyQt5.QtWidgets import QApplication, QWidget
from PyQt5.QtGui import QTextCursor

class worker(QThread):
    logChange = pyqtSignal(str)

    def __init__(self):
        super().__init__()

    def run(self):
        process = QProcess()
        command = f"mpiexec -n 8 test_mpi.exe"
        process.start(command)
        process.waitForStarted()
        self.stopFlag = False
        while True:
            if self.stopFlag:
                process.kill()
                process.waitForFinished(-1)
                self.logChange.emit("STOP!\n")
                break

            if process.waitForReadyRead(1000):
                output = process.readAllStandardOutput()
                output = bytearray(output).decode("gbk")
                self.logChange.emit(output)
            else:
                QApplication.processEvents()
                if process.state() == 0:
                    self.logChange.emit("FINISHED!\n")
                    break

    def stop(self):
        self.stopFlag = True

class Ui_Form(object):
    def setupUi(self, Form):
        Form.setObjectName("Form")
        Form.resize(400, 300)
        self.verticalLayout = QtWidgets.QVBoxLayout(Form)
        self.verticalLayout.setObjectName("verticalLayout")
        self.runButton = QtWidgets.QPushButton(Form)
        self.runButton.setObjectName("runButton")
        self.verticalLayout.addWidget(self.runButton)
        self.stopButton = QtWidgets.QPushButton(Form)
        self.stopButton.setObjectName("stopButton")
        self.verticalLayout.addWidget(self.stopButton)
        self.log = QtWidgets.QTextBrowser(Form)
        self.log.setObjectName("log")
        self.verticalLayout.addWidget(self.log)
        self.retranslateUi(Form)
        QtCore.QMetaObject.connectSlotsByName(Form)

    def retranslateUi(self, Form):
        _translate = QtCore.QCoreApplication.translate
        Form.setWindowTitle(_translate("Form", "Form"))
        self.runButton.setText(_translate("Form", "run"))
        self.stopButton.setText(_translate("Form", "stop"))

class MyWidget(QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)
        self.ui = Ui_Form()
        self.ui.setupUi(self)

    def logOutput(self, text):
        self.ui.log.insertPlainText(text)
        self.ui.log.moveCursor(QTextCursor.End)

    @QtCore.pyqtSlot()
    def on_runButton_clicked(self):
        self.logOutput("start running...\n")
        self.worker = worker()
        self.worker.logChange.connect(self.logOutput)
        self.worker.start()

    @QtCore.pyqtSlot()
    def on_stopButton_clicked(self):
        if self.worker:
            self.worker.stop()
            self.logOutput("stop running...\n")
            self.worker = None

if __name__ == "__main__":
    app = QApplication(sys.argv)
    widget = MyWidget()
    widget.show()
    sys.exit(app.exec_())

test_mpi.cc

#include "mpi.h"
#include <iostream>
#include <chrono>
#include <thread>

int main(int argc, char** argv) {
  using namespace std::chrono_literals;
  MPI_Init(NULL, NULL);

  int world_size;
  MPI_Comm_size(MPI_COMM_WORLD, &world_size);

  int world_rank;
  MPI_Comm_rank(MPI_COMM_WORLD, &world_rank);

  if (world_rank == 0) {
    for (int i = 0; i < 20; i++) {
      std::this_thread::sleep_for(1000ms);
      std::cout << "This output is from test mpi program: " << i << std::endl;
    }

    std::cout << "Finished!" << std::endl;
  }

  MPI_Finalize();
  return 0;
}

And I have learned I can kill it by using taskkill /IM test_mpi.exe /F, but this command will also terminate the test_mpi.exe started by other programs. So my question is how to clearly kill a mpi program which is launched by Qprocess.

[JonB]

@SJ2050
Your QProcess::start() only launches mpiexec, not test_mpi.exes. You cannot access the PIDs of the test_mpi.exes that spawns. At best you might be able to find those test_mpi.exes still running whose parent PID is the PID of the original mpiexec launched.

Forget QProcess. Tell us how from the command line you would kill exactly those spawned from the desired mpiexec and yet no others which might have been started elsewhere?

[SJ2050]

@JonB In command line, we usually kill a mpi program by killing one of the child processes. And I find this may be a bug of intel mpi on windows [ https://community.intel.com/t5/Intel-oneAPI-HPC-Toolkit/InteloneAPI-MPI-2021-2-0-behavior-on-Linux-and-Windows-differ/td-p/1290020 ]. Anyway, thanks for your reply.