diff --git a/rank-swapper-agent/.gitignore b/rank-swapper-agent/.gitignore
new file mode 100644
index 0000000000000000000000000000000000000000..f639b59cf707e0be382089316782ac90f2c4bc46
--- /dev/null
+++ b/rank-swapper-agent/.gitignore
@@ -0,0 +1,4 @@
+socket
+hello
+locserv
+*.o
diff --git a/rank-swapper-agent/Makefile b/rank-swapper-agent/Makefile
new file mode 100644
index 0000000000000000000000000000000000000000..7aefe6ec5f0320ff57f1066ca4fe63c46a9ddcaa
--- /dev/null
+++ b/rank-swapper-agent/Makefile
@@ -0,0 +1,25 @@
+export OMPI := /<path-to-my-openmpi-installation>/openmpi-install
+export PATH := $(PATH):$(OMPI)/bin
+export LD_LIBRARY_PATH := $(LD_LIBRARY_PATH):$(OMPI)/bin
+# requirement: GNU make, see https://unix.stackexchange.com/questions/11530/adding-directory-to-path-through-makefile/261844#261844
+
+CC = gcc
+SRC = locserv hello_c
+OBJ = $(SRC:.c=.o)
+CFLAGS = -W -Wall -Wextra -Wpedantic -pedantic
+
+.PHONY: clean
+
+all: locserv hello
+
+com_util.o: com_util.c
+ $(CC) $(CFLAGS) -c $<
+
+locserv: locserv.c com_util.o
+ $(CC) $(CFLAGS) -o $@ $< com_util.o
+
+hello: hello_c.c com_util.o
+ mpicc -o $@ $< com_util.o
+
+clean:
+ rm -f $(OBJ) com_util.o
diff --git a/rank-swapper-agent/README.md b/rank-swapper-agent/README.md
new file mode 100644
index 0000000000000000000000000000000000000000..d11311f35cec794be9ef2de5320e64d248a733fe
--- /dev/null
+++ b/rank-swapper-agent/README.md
@@ -0,0 +1,19 @@
+# OpenMPI Rank Swapper Agent
+
+0. Set the required environment variable `OMPI` which is most probably the path to your directory `openmpi-install` where the current OpenMPI-installation resides (just replace `<path-to-my-openmpi-installation>`). You can export it either in the `Makefile` (if a real MPI program should be run) or in the `client.sh` (if the test client should be run) or in your current shell if you do not mind repeating that for different shell instances.
+
+1. Compile everything:
+```shell
+make all
+```
+
+2. Starting the Agent/Server:
+```shell
+./server.sh
+```
+
+3. Starting the OpenMPI-Client (other MPI-Programs should also suffice):
+```shell
+./client.sh
+```
+
diff --git a/rank-swapper-agent/client.sh b/rank-swapper-agent/client.sh
new file mode 100755
index 0000000000000000000000000000000000000000..cb1d85889e5ee0f9657cf4452d3b32ee04aa9eef
--- /dev/null
+++ b/rank-swapper-agent/client.sh
@@ -0,0 +1,14 @@
+#!/bin/bash
+
+export OMPI=/<path-to-my-openmpi-installation>/openmpi-install
+export PATH=$PATH:$OMPI/bin
+export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$OMPI/bin
+
+PROCESSES=1
+
+HOSTFILE="--hostfile hostfile.txt"
+ENABLE_HYPERTHREADING="--bind-to hwthread"
+ALLOW_OVERLOAD="--bind-to core:overload-allowed"
+ENABLE_OVERSUBSCRIBE="--map-by :OVERSUBSCRIBE"
+# --bind-to hwthread: makes the usage of threads instead of just cores possible
+mpirun --np $PROCESSES $ALLOW_OVERLOAD $ENABLE_OVERSUBSCRIBE $HOSTFILE hello
diff --git a/rank-swapper-agent/com_util.c b/rank-swapper-agent/com_util.c
new file mode 100644
index 0000000000000000000000000000000000000000..5a2a40f1c1241d2d3c45aaa64fcd08aae8608139
--- /dev/null
+++ b/rank-swapper-agent/com_util.c
@@ -0,0 +1,23 @@
+/* Quelle: http://www.netzmafia.de/skripten/inetprog/ThomasSocket2.pdf */
+
+/* ------------------------------------------------------------------------------ */
+/* C-Quell-Modul com_util.c */
+/* ------------------------------------------------------------------------------ */
+/* Hilfsfunktionen, die in den Programmen für locserv und loccli */
+/* eingesetzt werden */
+/* ------------------------------------------------------------------------------ */
+
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+/* ------------------------------------------------------------------------------ */
+/* Ausgabe einer Meldung msg, gefolgt von der Fehlermeldung, die dem in errno */
+/* gespeicherten Fehlercode entspricht */
+/* anschließende Beendigung des Programms */
+
+void errorExit(char* msg) {
+ perror(msg);
+ exit(1);
+}
+
diff --git a/rank-swapper-agent/hello_c.c b/rank-swapper-agent/hello_c.c
new file mode 100644
index 0000000000000000000000000000000000000000..d8b3e6111762a2a5f8010d7eda71b1b6c37faddc
--- /dev/null
+++ b/rank-swapper-agent/hello_c.c
@@ -0,0 +1,147 @@
+/*
+ * Copyright (c) 2004-2006 The Trustees of Indiana University and Indiana
+ * University Research and Technology
+ * Corporation. All rights reserved.
+ * Copyright (c) 2006 Cisco Systems, Inc. All rights reserved.
+ *
+ * Sample MPI "hello world" application in C
+ */
+
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+
+#include "mpi.h"
+
+#define SOCKET_PATH "/home/beach/Dokumente/Uni/Informatik_BA/Bachelorarbeit_MPI/sockets_mpi_test/socket"
+#define BUFFLEN 64
+
+/* Spawn Modes (dynamic job spawning):
+ * 1: Spawn just one process (in one job)
+ * 2: Spawn 2 processes in 2 different jobs
+ * 3: Spawn 2 prcoesses in one (shared) job
+ * 0 or other: Do not spawn a dynamic process/job
+ */
+#define SPAWN_MODE 0
+
+void errorExit(char* msg);
+
+/*void notifyProcessAgent(pid_t pid, int rank, const char *eventInfo) {
+ struct sockaddr_un strAddr;
+ socklen_t lenAddr;
+ int fdSock;
+
+ if ((fdSock=socket(PF_UNIX, SOCK_STREAM, 0)) < 0) {
+ errorExit("socket");
+ }
+
+ strAddr.sun_family=AF_LOCAL; // Unix domain
+ strcpy(strAddr.sun_path, SOCKET_PATH);
+ lenAddr=sizeof(strAddr.sun_family)+strlen(strAddr.sun_path);
+ if (connect(fdSock, (struct sockaddr*)&strAddr, lenAddr) !=0 ) {
+ errorExit("connect");
+ }
+
+ char info2Send[BUFFLEN];
+ snprintf(info2Send, BUFFLEN+1, "%s: %d, %d", eventInfo, pid, rank);
+ if (send(fdSock, info2Send, BUFFLEN+1, 0) < 0) {
+ errorExit("send");
+ }
+ printf("\nData send!\n");
+
+ char rank2Recv[BUFFLEN];
+ recv(fdSock, rank2Recv, BUFFLEN+1, 0);
+ int receivedNumber = (int)strtol(rank2Recv, NULL, 0);
+ printf("Received from server: %d\n", receivedNumber);
+
+ close(fdSock);
+}*/
+
+int main(int argc, char* argv[]) {
+
+ int rank, size, len;
+ pid_t pid;
+ char version[MPI_MAX_LIBRARY_VERSION_STRING];
+
+ MPI_Init(&argc, &argv);
+ MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+ MPI_Comm_size(MPI_COMM_WORLD, &size);
+
+ pid = getpid();
+
+ //notifyProcessAgent(pid, rank, "Spawned");
+
+ printf("Hello, world, I am %d of %d, PID: %d\n", rank, size, pid);
+
+ // dynamically spawn child process
+ // https://mpi.deino.net/mpi_functions/MPI_Comm_spawn.html
+ if (1 == SPAWN_MODE) {
+
+ int np = 1;
+ int errcodes[1];
+ MPI_Comm parentcomm, intercomm;
+ MPI_Comm_get_parent( &parentcomm );
+ if (parentcomm == MPI_COMM_NULL) {
+ MPI_Comm_spawn( "hello", MPI_ARGV_NULL, np, MPI_INFO_NULL, 0,
+ MPI_COMM_WORLD, &intercomm, errcodes );
+ printf("I'm the parent.\n");
+ } else {
+ printf("I'm the spawned.\n");
+ }
+ if (0 != errcodes[0]) {
+ printf("ERROR_SPAWN: code: %d\n", errcodes[0]);
+ }
+
+ // (instead of Comm_multiple) spawns a second, different intercommunicator
+ } else if (2 == SPAWN_MODE) {
+
+ int np = 1;
+ int errcodes[1];
+ MPI_Comm parentcomm, intercomm;
+ MPI_Comm_get_parent( &parentcomm );
+ if (parentcomm == MPI_COMM_NULL) {
+ for (int i = 0; i < 2; i++) {
+ MPI_Comm_spawn( "hello", MPI_ARGV_NULL, np, MPI_INFO_NULL, 0,
+ MPI_COMM_WORLD, &intercomm, errcodes );
+ if (0 != errcodes[0]) {
+ printf("ERROR_SPAWN: code: %d\n", errcodes[0]);
+ }
+ }
+ printf("I'm the parent.\n");
+ } else {
+ printf("I'm the spawned.\n");
+ }
+
+ } else if (3 == SPAWN_MODE) {
+
+ int np[2] = { 1, 1 };
+ int errcodes[2];
+ MPI_Comm parentcomm, intercomm;
+ char *cmds[2] = { "hello", "hello" };
+ MPI_Info infos[2] = { MPI_INFO_NULL, MPI_INFO_NULL };
+ MPI_Comm_get_parent( &parentcomm );
+ if (parentcomm == MPI_COMM_NULL) {
+ // Create n more processes using the "hello" executable
+ MPI_Comm_spawn_multiple(2, cmds, MPI_ARGVS_NULL, np, infos, 0, MPI_COMM_WORLD, &intercomm, errcodes );
+ printf("I'm the parent.\n");
+ } else {
+ printf("I'm the spawned.\n");
+ }
+ for (int i = 0; i < 2; i++) {
+ if (0 != errcodes[i]) {
+ printf("ERROR_SPAWN: code: %d\n", errcodes[i]);
+ }
+ }
+ }
+
+ sleep(5);
+
+ MPI_Finalize();
+
+ //notifyProcessAgent(pid, rank, "Ended");
+
+ return 0;
+}
+
diff --git a/rank-swapper-agent/hostfile.txt b/rank-swapper-agent/hostfile.txt
new file mode 100644
index 0000000000000000000000000000000000000000..69990516239c4520dc38c1451f54565aa29dc508
--- /dev/null
+++ b/rank-swapper-agent/hostfile.txt
@@ -0,0 +1 @@
+localhost slots=4 max-slots=4
diff --git a/rank-swapper-agent/locserv.c b/rank-swapper-agent/locserv.c
new file mode 100644
index 0000000000000000000000000000000000000000..828ae8e66770e6e0ae51300adc1c7b903303a601
--- /dev/null
+++ b/rank-swapper-agent/locserv.c
@@ -0,0 +1,189 @@
+/* Quelle: http://www.netzmafia.de/skripten/inetprog/ThomasSocket2.pdf */
+
+/* ------------------------------------------------------------------------------- */
+/* Programm locserv */
+/* ------------------------------------------------------------------------------- */
+/* Beispiel fuer Unix Domain Sockets */
+/* Einfacher Serverprozeß, */
+/* - der auf einen Verbindungswunsch durch einen Clientprozeß wartet, */
+/* - einen Verbindungswunsch akzeptiert */
+/* - und die ihm vom Clientprozeß geschickten Daten an die Standardausgabe ausgibt */
+/* Wenn der Clientprozeß die Kommunikation durch Senden von EOF (=CTRL-D) beendet, */
+/* wartet er auf den nächsten Verbindungswunsch */
+/* ------------------------------------------------------------------------------- */
+
+#include <search.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+#include <stdlib.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <time.h>
+#include <unistd.h>
+
+#define SOCKET_PATH "/home/beach/Dokumente/Uni/Informatik_BA/Bachelorarbeit_MPI/sockets_mpi_test/socket"
+#define MAX_CONNECTIONS 10
+#define RANK_STR_LEN 8
+#define BUFFLEN 64
+
+/* hashtable info source:
+ * https://pubs.opengroup.org/onlinepubs/9699919799/functions/hcreate.html,
+ * https://linux.die.net/man/3/hsearch_r
+ *
+ * number of different ranks of processes in different jobs plus number of
+ * different job (which equals the number of ranks in worst case)
+ */
+#define NUM_RANKS 100
+
+void errorExit(char* msg);
+
+/* storage for the hashmap
+ * (The hashtable works exclusively with pointers so it is necessary to
+ * allocate something to put the data in to be pointed to by the hashtable)
+ */
+typedef struct HashStorage{
+ char keys[NUM_RANKS][32]; // stores the different keys [<jobid>:<vpid>] or [<jobid>]
+ int key_index; // the current point in the key array that can be written to
+ int data[NUM_RANKS]; // stores the different ranks and current job max ranks that the hashtable needs to point at
+ int data_index; // the current point in the data array that can be written to
+} HashStorage;
+
+/* Stores the given jobid as the items key */
+void setKeyJobid(uint32_t jobid, char* key_str, ENTRY* item) {
+ sprintf(key_str, "%u", jobid);
+ item->key = key_str;
+}
+
+/* Sets a combination (<jobid>:<vpid>) of the given jobid and vpid as the items key */
+void setKeyJobidVpid(uint32_t jobid, uint32_t vpid, char* key_str, ENTRY* item) {
+ sprintf(key_str, "%u:%u", jobid, vpid);
+ // check if rank is already assigned to a certain jobid+vpid combination
+ item->key = key_str;
+}
+
+/* Put an item of the given value with the given key into the table */
+void putValueIntoTable(int value, char* key_str, HashStorage* hstorage, ENTRY* item) {
+ strcpy(hstorage->keys[hstorage->key_index], key_str);
+ item->key = hstorage->keys[hstorage->key_index];
+ hstorage->data[hstorage->data_index] = value;
+ item->data = &(hstorage->data[hstorage->data_index]);
+ // actually put the pointers (key, data) into the hashtable
+ if (NULL == hsearch(*item, ENTER)) {
+ errorExit("hsearch");
+ }
+ // increment the pointer to the next free places in the storage arrays
+ hstorage->data_index++;
+ hstorage->key_index++;
+}
+
+/* Returns the desired vpid (which equals the rank later on in Comm_init()) by
+ * either retrieving it from the hashtable if it is already known or by setting
+ * it to the maximum currently usable rank per jobid (which is 0 if no other
+ * processes with the same jobid has yet been seen)
+ */
+uint32_t getDesiredVpid(uint32_t jobid, uint32_t vpid, size_t size, HashStorage* hstorage) {
+ ENTRY item;
+ ENTRY *found_item; // Name to look for in table.
+ char key_str[16];
+
+ setKeyJobidVpid(jobid, vpid, key_str, &item);
+ if ((found_item = hsearch(item, FIND)) != NULL) {
+ printf("Found Process: %u:%u -> %d\n", jobid, vpid, *((int *)found_item->data));
+ // just return the already chosen vpid if the process (name) is known
+ return *((int *)found_item->data);
+ } else {
+ setKeyJobid(jobid, key_str, &item);
+ if ((found_item = hsearch(item, FIND)) != NULL) {
+ // increment maximum stored vpid to remember which vpids are
+ // already (ascendingly) assigned
+ int stored_vpid_count = ++(*((int *)found_item->data));
+ // descendingly generate vpid/rank to demonstrate that the order is
+ // not important anymore
+ int new_vpid = (size - 1) - stored_vpid_count;
+ printf("Found Job: %u -> %d\n", jobid, new_vpid);
+ // update the maximum stored vpid
+ putValueIntoTable(stored_vpid_count, key_str, hstorage, &item);
+ // store the process name (which gets a randomized rank)
+ setKeyJobidVpid(jobid, vpid, key_str, &item);
+ putValueIntoTable(new_vpid, key_str, hstorage, &item);
+ return new_vpid;
+ } else {
+ int new_vpid = size - 1;
+ printf("Nothing found: %u -> %d\n", jobid, new_vpid);
+ // initialize the stored maximum vpid
+ putValueIntoTable(0, key_str, hstorage, &item);
+ // store the process name (which gets a randomized rank)
+ setKeyJobidVpid(jobid, vpid, key_str, &item);
+ putValueIntoTable(new_vpid, key_str, hstorage, &item);
+ return new_vpid;
+ }
+ }
+}
+
+int main(void) {
+
+ char client_message[BUFFLEN];
+
+ struct sockaddr_un strAddr;
+ socklen_t lenAddr;
+ int fdSock;
+ int fdConn;
+
+ if ((fdSock=socket(PF_UNIX, SOCK_STREAM, 0)) < 0) {
+ errorExit("socket");
+ }
+
+ unlink (SOCKET_PATH); /* Sicherstellung, daß SOCKET_PATH nicht existiert */
+ strAddr.sun_family=AF_LOCAL; /* Unix Domain */
+ strcpy(strAddr.sun_path, SOCKET_PATH);
+ lenAddr=sizeof(strAddr.sun_family)+strlen(strAddr.sun_path);
+ if (bind(fdSock, (struct sockaddr*)&strAddr, lenAddr) != 0) {
+ errorExit("bind");
+ }
+
+ if (listen(fdSock, MAX_CONNECTIONS) != 0) {
+ errorExit("listen");
+ }
+
+ // create hashtable with two different types of key-data-combinations:
+ // 1. <jobid>:<desired_rank> -> vpid
+ // 2. <jobid> -> job_max_rank
+ (void) hcreate(NUM_RANKS);
+
+ // initialize hsearch storage
+ struct HashStorage hstorage = { .key_index = 0, .data_index = 0 };
+
+ while ((fdConn=accept(fdSock, (struct sockaddr*)&strAddr, &lenAddr)) >= 0) {
+
+ // since recv() seems to be atomar, no concurrent behaviour must be
+ // considered
+ recv(fdConn , client_message , BUFFLEN , 0);
+ printf("%s\n", client_message);
+
+ pid_t pid;
+ uint32_t vpid;
+ uint32_t jobid;
+ size_t size;
+ sscanf(client_message, "Spawned - PID: %d, vpid: %u, jobID: %u, size: %zu", &pid, &vpid, &jobid, &size);
+ //printf("\nCheck: PID: %d, vpid: %u, jobID: %u, size: %zu", pid, vpid, jobid, size);
+
+ uint32_t desiredRank = getDesiredVpid(jobid, vpid, size, &hstorage);
+
+ char rankString[RANK_STR_LEN];
+ snprintf(rankString, RANK_STR_LEN+1, "%u", desiredRank);
+ if (send(fdConn, rankString, RANK_STR_LEN+1, 0) < 0) {
+ errorExit("send");
+ }
+ printf("Send Rank: %d\n\n", desiredRank);
+
+ close(fdConn);
+ }
+ hdestroy();
+
+ close(fdSock);
+
+ return 0;
+}
+
diff --git a/rank-swapper-agent/server.sh b/rank-swapper-agent/server.sh
new file mode 100755
index 0000000000000000000000000000000000000000..2f2bdcdf5cad1c7f6d55370f8b93d44e3523869a
--- /dev/null
+++ b/rank-swapper-agent/server.sh
@@ -0,0 +1,3 @@
+#!/bin/bash
+
+./locserv