add: task2

.env

@@ -0,0 +1 @@
+TASK_TO_RUN=task2

Dockerfile

@@ -16,10 +16,13 @@ RUN chmod 600 /root/.ssh/authorized_keys
 RUN echo "Host *\n\tStrictHostKeyChecking no" >> /root/.ssh/config
 RUN sed -i 's/#PermitRootLogin prohibit-password/PermitRootLogin yes/' /etc/ssh/sshd_config
 
+# ... (all previous lines are the same) ...
+
 WORKDIR /app
 
 COPY . /app/
 
 # Compile ALL the necessary tasks during the build
 RUN mpic++ -O2 -std=c++17 -o mpi_task task.cpp
-RUN mpic++ -O2 -std=c++17 -o task1 task1.cpp
+RUN mpic++ -O2 -std=c++17 -o task1 task1.cpp
+RUN mpic++ -O2 -std=c++17 -o task2 task2.cpp # <-- ADD THIS LINE

docker-compose.yml

@@ -2,14 +2,13 @@ services:
   master:
     build: .
     container_name: pdc-master
-    # REMOVED the 'hostname:' line
     volumes:
       - ./hostfile:/app/hostfile
-    # ADDED the 'environment:' block
     environment:
       - FRIENDLY_NAME=pdc-master
+    # This line automatically reads from the .env file
     command: >
-      sh -c "/usr/sbin/sshd & sleep 5 && mpirun -np 5 --hostfile /app/hostfile --allow-run-as-root /app/task1"
+      sh -c "/usr/sbin/sshd & sleep 5 && mpirun -np 5 --hostfile /app/hostfile --allow-run-as-root /app/${TASK_TO_RUN:-task1}"
     networks:
       - pdcn
 

task1.cpp

@@ -4,6 +4,8 @@
 #include <unistd.h> // Required for gethostname() and getpid()
 #include <cstdlib>  // Required for getenv()
 
+// Roll numbers: 22i-1601, 22i-1554, 22i-1689
+
 int main(int argc, char** argv) {
     MPI_Init(&argc, &argv);
 

task2.cpp

@@ -0,0 +1,90 @@
+#include <iostream>
+#include <vector>
+#include <mpi.h>
+#include <unistd.h> // Required for gethostname() and getpid()
+#include <cstdlib>  // Required for getenv()
+#include <string>   // Required for std::string
+
+int main(int argc, char** argv) {
+    MPI_Init(&argc, &argv);
+
+    int world_size;
+    MPI_Comm_size(MPI_COMM_WORLD, &world_size);
+
+    int world_rank;
+    MPI_Comm_rank(MPI_COMM_WORLD, &world_rank);
+
+    char container_id[256];
+    gethostname(container_id, sizeof(container_id));
+    const char* friendly_name = getenv("FRIENDLY_NAME");
+    if (friendly_name == nullptr) { friendly_name = "unknown"; }
+    pid_t pid = getpid();
+    int num_workers = world_size - 1;
+
+    if (world_rank == 0) {
+        // --- MASTER PROCESS ---
+
+        // Q2. Master has an array {2,3,4,5}.
+        int data[] = {2, 3, 4, 5};
+        int data_count = sizeof(data) / sizeof(int);
+
+        if (data_count != num_workers) {
+            std::cerr << "Error: This task requires exactly 4 workers (" << num_workers 
+                      << " found). Please run with -np 5." << std::endl;
+            MPI_Abort(MPI_COMM_WORLD, 1);
+        }
+
+        std::cout << "Master on " << friendly_name << " (ID: " << container_id << ", PID: " << pid 
+                  << ", rank: 0): distributing array {2,3,4,5} to workers." << std::endl;
+
+        for (int i = 0; i < num_workers; ++i) {
+            MPI_Send(&data[i], 1, MPI_INT, i + 1, 0, MPI_COMM_WORLD);
+        }
+
+        std::vector<int> results(num_workers);
+        for (int i = 0; i < num_workers; ++i) {
+            int received_result;
+            MPI_Recv(&received_result, 1, MPI_INT, i + 1, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
+            results[i] = received_result;
+        }
+
+        std::cout << "Master on " << friendly_name << " (ID: " << container_id << ", PID: " << pid 
+                  << ", rank: 0): gathered results {";
+        for (int i = 0; i < results.size(); ++i) {
+            std::cout << results[i] << (i == results.size() - 1 ? "" : ",");
+        }
+        std::cout << "}" << std::endl;
+
+    } else {
+        // --- WORKER PROCESSES ---
+        int received_number;
+        MPI_Recv(&received_number, 1, MPI_INT, 0, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
+
+        int computed_result = 0;
+        std::string operation_string;
+
+        // Q2. Different workers perform different computations based on their rank.
+        if (world_rank == 1) {
+            computed_result = received_number * received_number;
+            operation_string = "squared ->";
+        } else if (world_rank == 2) {
+            computed_result = received_number * received_number * received_number;
+            operation_string = "cubed ->";
+        } else if (world_rank == 3) {
+            computed_result = received_number * 2;
+            operation_string = "doubled ->";
+        } else if (world_rank == 4) {
+            computed_result = received_number - 1;
+            operation_string = "subtracted 1 ->";
+        }
+
+        std::cout << "Worker on " << friendly_name << " (ID: " << container_id << ", PID: " << pid 
+                  << ", rank: " << world_rank << "): received " << received_number 
+                  << ", " << operation_string << " " << computed_result << std::endl;
+        
+        MPI_Send(&computed_result, 1, MPI_INT, 0, 0, MPI_COMM_WORLD);
+    }
+
+    MPI_Finalize();
+    return 0;
+}