Debugging MPI Program on M1

[Asterix9000]

Hi,

I am currently in the process of setting up my vscode debugging environment for debugging an MPI project on my new M1 macbook. I have spent several days trying to get this setup and am at a bit of a loss as to how to proceed. Any help would be much appreciated.

Describe the bug

• OS and Version: macOS Monterey Version 12.1
• VS Code Version: 1.63.2
• C/C++ Extension Version: CodeLLDB v1.6.10
• Compiler: mpich 3.4.3

I started setting everything up by following these two tutorials:
https://iamsorush.com/posts/debug-mpi-vs-code/
https://medium.com/@li.nguyen_15905/setting-up-vscode-for-mpi-programming-b6665da6b4ad

I installed the CodeLLDB extension per the suggestion in:
microsoft/vscode-cpptools#6779

I also referred to this thread as I was trying to set everything up:
microsoft/vscode-cpptools#1723

After starting the MPI program I attempt to attach the debugger to one of the processes, which yields the following error:

more than one process named ~/Projects/MPI/debug_test/build/test.exe:
PID PARENT USER TRIPLE ARGUMENTS
====== ====== ========== ============================== ============================
76022 76018 user arm64-apple-* ./test.exe
76021 76018 user arm64-apple-* ./test.exe
76020 76018 user arm64-apple-* ./test.exe
76019 76018 user arm64-apple-* ./test.exe

To Reproduce

Here is a simple reproducer program, along with corresponding CMakeLists.txt, build script, launch.json, tasks.json, and c_cpp_properties.json . To reproduce the issue copy the .json files, install the CodeLLDB extension, build the reproducer, then run it with mpirun -np 4 ./test.exe ( not sure if this issue is specific to M1 yet ). Note that this requires a working version of MPI, which I installed using homebrew.

Simple reproducer:

#include <mpi.h>
#include <unistd.h>
#include <iostream>

using namespace std;

int main(){

    {
        int i=0;
        while (0 == i)
            sleep(5);
    }

    MPI_Init(NULL, NULL);
    int rank,size;
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
    MPI_Comm_size(MPI_COMM_WORLD, &size);

    char data = 'A';
    
    if (rank==0) {
        data = 'B';
        // cout << "hello from rank 0" << endl;
        MPI_Send( &data , 1 , MPI_INT , 1 , 0 , MPI_COMM_WORLD);
    }
    else if (rank==1){
        // cout << "hello from rank 1" << endl;
        MPI_Recv( &data , 1 , MPI_INT , 0 , 0 , MPI_COMM_WORLD , MPI_STATUS_IGNORE);
    }

    cout << "hello from rank " << rank << endl;

return 0;

}

CMakeLists.txt:

cmake_minimum_required(VERSION 3.10)

# set the project name
project(Hello)

# add the executable
add_executable(Hello hello.cpp)

find_package(MPI REQUIRED)

message(STATUS " MPI_CXX_FOUND = ${MPI_CXX_FOUND}" )

include_directories(${MPI_CXX_INCLUDE_PATH})

add_executable(test.exe hello.cpp)

target_link_libraries(test.exe ${MPI_CXX_LIBRARIES})

build script:

#!/bin/bash

rm -f CMakeCache.txt;
rm -rf CMakeFiles

cmake \
    -D CMAKE_CXX_COMPILER=/opt/homebrew/Cellar/mpich/3.4.3/bin/mpic++ \
    -D CMAKE_C_COMPILER=/opt/homebrew/Cellar/mpich/3.4.3/bin/mpicc \
    -D CMAKE_BUILD_TYPE=Debug \
    -D CMAKE_OSX_ARCHITECTURES=arm64 \
    ..

launch.json:

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [
        {
            "name": "dist_test",
            "type": "lldb",
            "request": "attach",
            "processId": "${command:pickMyProcess}",
            "program": "~/Desktop/Projects/MPI/debug_test/build/test.exe",
            "MIMode": "lldb",
            "preLaunchTask": "mpich build active file",
            "targetArchitecture": "arm64"
        }
    ]
}

task.json:

{
    "tasks": [
        {
            "type": "shell",
            "label": "mpich build active file",
            "command": "/opt/homebrew/Cellar/mpich/3.4.3/bin/mpic++",
            "args": [
                "-fdiagnostics-color=always",
                "-g",
                "${file}",
                "-o",
                "${fileDirname}/${fileBasenameNoExtension}"
            ],
            "group": {
                "kind": "build",
                "isDefault": true
            }
        }
    ],
    "version": "2.0.0"
}

c_cpp_properties.json:

{
    "configurations": [
        {
            "name": "Mac",
            "includePath": [
                "${workspaceFolder}/**",
                "/opt/homebrew/Cellar/mpich/3.4.3/include"
            ],
            "defines": [],
            "macFrameworkPath": [],
            "compilerPath": "/opt/homebrew/Cellar/mpich/3.4.3/bin/mpic++"
        }
    ],
    "version": 4
}

[vadimcn]

Well, attaching by program name is not going work in your case, because there's more than one instance of that program running. How would the debugger know which one you wanted to debug? Try removing the "program" attribute from launch configuration.

[Asterix9000]

Thank you for your insightful comments. After removing the program name from the launch.json it started working. For those viewing this discussion in the future, here are the final .json files:

launch.json:

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [
        {
            "name": "dist_test",
            "type": "lldb",
            "lldb.verboseLogging":true,
            "request": "attach",
            "pid": "${command:pickMyProcess}",
            "MIMode": "lldb",
            "preLaunchTask": "mpich build active file",
            "targetArchitecture": "arm64"
        }
    ]
}

tasks.json:

{
    "tasks": [
        {
            "type": "shell",
            "label": "mpich build active file",
            "command": "/opt/homebrew/Cellar/mpich/3.4.3/bin/mpic++",
            "args": [
                "-fdiagnostics-color=always",
                "-g",
                "${file}",
                "-o",
                "${fileDirname}/${fileBasenameNoExtension}"
            ],
            "group": {
                "kind": "build",
                "isDefault": true
            }
        }
    ],
    "version": "2.0.0"
}

c_cpp_properties.json:

{
    "configurations": [
        {
            "name": "Mac",
            "includePath": [
                "${workspaceFolder}/**",
                "/opt/homebrew/Cellar/mpich/3.4.3/include"
            ],
            "defines": [],
            "macFrameworkPath": [],
            "compilerPath": "/opt/homebrew/Cellar/mpich/3.4.3/bin/mpic++"
        }
    ],
    "version": 4
}

reproducer:

#include <mpi.h>
#include <unistd.h>
#include <iostream>

using namespace std;

int main(){

    

    MPI_Init(NULL, NULL);
    int rank,size;
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
    MPI_Comm_size(MPI_COMM_WORLD, &size);

    {
        int i=0;
        while (0 == i)
            sleep(5);
    }

    char data = 'A';
    
    if (rank==0) {
        data = 'B';
        // cout << "hello from rank 0" << endl;
        MPI_Send( &data , 1 , MPI_INT , 1 , 0 , MPI_COMM_WORLD);
    }
    else if (rank==1){
        // cout << "hello from rank 1" << endl;
        MPI_Recv( &data , 1 , MPI_INT , 0 , 0 , MPI_COMM_WORLD , MPI_STATUS_IGNORE);
    }

    cout << "hello from rank " << rank << endl;

    MPI_Barrier(MPI_COMM_WORLD);
    MPI_Finalize();

return 0;

}