CS3103 Hotdog Factory

Introduction

Consider a factory with 30 machines M_i (1 <= i <= 30) making hot dogs and another 25 machines P_j (1 <= j <= 25) packing hot dogs. The hot dogs will be first made by the making machines and then sent to a hot dog pool [Note 1]. The packing machines will take hot dogs from the pool for packing. The manager of the factory specifies the number of hot dogs need to be done, N [Note 2]. There is a log file containing records for logging when a hot dog is packed. When all the hot dogs are done, the manager will append a summary to the log file.

Tasks

Using Pthreads and mutex, design and implement a multithreaded C++ program under Linux that works as follows:

Each making machine is modeled with a making thread (created by the master thread).

• A making machine starts with checking the remaining number of hot dogs to be made.
• The making machine makes one hot dog at a time.
• The making machine takes 4 to 6 seconds [Note 3] to make one hot dog.
• After a hot dog is made, the making machine takes 1 to 2 seconds to send the hot dog together with its machine id, i, to the hot dog pool.
• Once the making machine finishes sending the hot dog, it can start to make the next hot dog.
• When the required number of hot dogs is made, the making machine stops

Each packing machine is modeled with a packing thread (created by the master thread).

• A packing machine starts with checking if there is any hot dog in the pool.
• If there are hot dogs in the pool, the packing machine takes 1 to 2 seconds to take a hot dog from the pool, one at a time.
• After taking a hot dog from the pool, the packing machine takes 1 to 2 seconds to pack the hot dog.
• After packing the hot dog, the packing machine writes a record to the log file in form of < hot_dog_id, i, j >, where hot_dog_id is a serial number of the packed hot dog (counting from 1 to N), i is the making machine id and j is the packing machine id.
• The packing machine takes 1 to 2 seconds to write a record to the log file.
• Once the packing machine finishes writing the record, it can start to pack the next hot dog.
• When all the hot dogs are packed, the packing machine stops.

A master thread is created to model the manager of the factory.

• The manager specifies the number of hot dogs to be done, N.
• The manager initiates 30 making and 25 packing machines with machine id i and j respectively, where 1 <= i <= 30 and 1 <= j <= 25.
• The manager has to wait until all machines stop, i.e., all hot dogs are made and packed and all records are written in the log file.
• After all machines stop, the manager reads the log file and appends the following summary to the log file:
  • The number of hot dogs made and packed by each machine, in form of < machine type (M or P), machine id (i or j), number of hot dogs made or packed >
  • The total number of hot dogs made and packed, in form of < total number of hot dogs made, total number of hot dogs packed>

Notes:

1. There is NO specific insertion/removal order for the hot dog pool. If you need to enforce a certain order, specify this assumption clearly as a comment in your program.

2. The number of hot dogs need to be done should be an input value to your program

3. To simulate the time taken for a thread to finish a step, you can make the thread sleep for a random period of time. For example, sleep(rand()%3+4) can be used to simulate the time taken for a making machine to make a hot dog, ranging from 4 to 6 seconds (http://linux.die.net/man/3/sleep, http://www.tutorialspoint.com/cplusplus/cpp_numbers.htm).

Flowchart (for reference only)

See image: flowchart.