From a34c9714ab5e4f83deb7a72efe78b807229ca52c Mon Sep 17 00:00:00 2001
From: Michael Krayer <michael.krayer@posteo.de>
Date: Tue, 19 Jan 2021 13:13:42 +0100
Subject: [PATCH] initial commit

---
 README.md         |  8 ++++
 build             |  2 +
 src/mkparallel.cc | 93 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 103 insertions(+)
 create mode 100644 README.md
 create mode 100755 build
 create mode 100644 src/mkparallel.cc

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..b4e4865
--- /dev/null
+++ b/README.md
@@ -0,0 +1,8 @@
+mkparallel
+---
+Execute a serial command embarassingly parallel.
+Usage:
+mpirun -n <nproc>  mkparallel <command> <digits>
+
+<command> is the command to be executed where every occurence of {} will be replaced by the rank of the processor.
+The rank can be padded with leading zeros by specifying <digits> with a value greater than zero.
diff --git a/build b/build
new file mode 100755
index 0000000..26ca250
--- /dev/null
+++ b/build
@@ -0,0 +1,2 @@
+#!/bin/bash
+mpicxx -o mkparallel src/mkparallel.cc
diff --git a/src/mkparallel.cc b/src/mkparallel.cc
new file mode 100644
index 0000000..a31a5e5
--- /dev/null
+++ b/src/mkparallel.cc
@@ -0,0 +1,93 @@
+#include <cstdlib>
+#include <iostream>
+#include <string>
+#include <stdexcept>
+#include <mpi.h>
+
+using namespace std;
+
+string toStringZeroPadded(int,int);
+void replaceAll(string&r,const string&,const string&);
+
+int main(int argc,char *argv[])
+{
+  int ierr;
+  int nproc;
+  int rank;
+  MPI_Status status;
+  
+  ierr = MPI_Init(&argc,&argv);
+  ierr = MPI_Comm_rank(MPI_COMM_WORLD,&rank);
+  ierr = MPI_Comm_size(MPI_COMM_WORLD,&nproc);
+ 
+  // Check positional arguments
+  if(argc!=3){
+    cerr << "Usage: mpirun -n " << nproc << " " << argv[0] << " <cmd> <digits>\n"
+         << "  <cmd>      command to be executed embarassingly parallel. {} is replaced by rank\n"
+         << "  <digits>   number of leading zeros for rank replacement\n";
+    MPI_Finalize();
+    return 1;
+  }
+
+  // Parse command line arguments
+  string arg_cmd    = argv[1];
+  string arg_digits = argv[2]; 
+  int digits;
+  try{
+    digits = stoi(arg_digits);
+  }
+  catch(const invalid_argument& ia){
+    cerr << "Invalid argument to " << ia.what() << ": " << arg_digits << endl;
+    return 2;
+  }
+
+  // Construct command to be executed
+  string str_cmd  = arg_cmd;
+  string str_rank;
+  if(digits>0)
+    str_rank = toStringZeroPadded(rank,digits);
+  else
+    str_rank = to_string(rank);
+  replaceAll(str_cmd,"{}",str_rank);
+  cerr << "Rank " << rank << " is executing: " << str_cmd << endl;
+  
+  // Run command and return exit code
+  int exitcode = system(str_cmd.c_str());
+  cerr << "Rank " << rank << " finished with exitcode "  << exitcode << endl;
+
+  // Finalize
+  MPI_Finalize();
+  return 0;
+}
+
+string toStringZeroPadded(int val,int pad){
+  char tmp[pad];
+  string str;
+  sprintf(tmp,"%0*d",pad,val);
+  str = tmp;
+  return str;
+}
+
+void replaceAll(string& str,const string& from,const string& to){
+    if(from.empty())
+        return;
+    size_t start_pos = 0;
+    while((start_pos=str.find(from,start_pos))!=string::npos){
+      str.replace(start_pos,from.length(),to);
+      start_pos+=to.length(); // In case 'to' contains 'from', like replacing 'x' with 'yx'
+    }
+}
+
+/*
+int checkMpiError(int ierr){
+  char msg[MPI_MAX_ERROR_STRING];
+  int msglen, ierr2;
+  if(ierr!=0){
+    ierr2 = MPI_Error_string(ierr,msg,&msglen);
+    cout << msg << endl;
+    return ierr2;
+  }
+  else
+    return 0;
+}
+*/