Month: May 2016

Java Monitor (classic reader-writer problem) 1 writer & 2 readers

JavaMultithreadMonitor

The writer fills data until the buffer is full. If the buffer is full (condition variable), then waits. Otherwise (i.e., the buffer is available), it fills data in the buffer. After that, it signals.

The reader reads data until the buffer is empty. If the buffer is empty (condition variable), then wait. Otherwise (i.e., the buffer is available), it reads data. After that, it signals.

NOTE: BinarySemaphore is the same as Mutex (for one shared resource).

1. SharedMemoryBinarySemaphoreWriter & SharedMemoryBinarySemaphoreReader
First, run SharedMemoryBinarySemaphoreWriter.exe (this only writes data on the shared memory segment.)

SharedMemoryBinarySemaphoreWriter

Then, run SharedMemoryBinarySemaphoreReader.exe (it only reads data from the shared memory segment.)

SharedMemoryBinarySemaphoreReader

2. SharedMemoryBinarySemaphoreMasterSlave (Both master/slaves write/reads data to/from the shared memory segment.)
First, run SharedMemoryBinarySemaphoreMasterSlave.exe –master
Then, run SharedMemoryBinarySemaphoreMasterSlave.exe

SharedMemoryBinarySemaphoreMasterSlave

NOTE: Semaphore allows a specific number of processes/threads to enter.

3. SharedMemoryGeneralSemaphoreMasterSlave (classic reader-writer problem)

The writer fills data until the buffer is full. It waits emptyBufferSemaphore (e–) to be available. If so, it fills data. After that, it signals fullBufferSemaphore(f++) ready.

The reader reads data until the buffer is empty. It waits fullBufferSemaphore(f–) to be available. If so, it reads data. After that, it signals emptyBufferSemaphore(e++) to be ready.

1 master is the writer (fills data the shared memory buffer).

2 slaves are the readers (read data from the shared memory buffer; but their reader index must be synchronized).
First, run SharedMemoryGeneralSemaphoreMasterSlave.exe –master
Next, run SharedMemoryGeneralSemaphoreMasterSlave.exe
Then, run SharedMemoryGeneralSemaphoreMasterSlave.exe

SharedMemoryGeneralSemaphoreMasterSlave

1. SharedMemoryMutexWriter & SharedMemoryMutexReader
First, run SharedMemoryMutexWriter.exe (this only writes data on the shared memory segment.)
SharedMemoryMutexWriter

Then, run SharedMemoryMutexReader.exe (it only reads data from the shared memory segment.)
SharedMemoryMutexReader

2. SharedMemoryMutexMasterSlave (Both master/slaves write/reads data to/from the shared memory segment.)
First, run SharedMemoryMutexMasterSlave.exe –master
Then, run SharedMemoryMutexMasterSlave.exe
SharedMemoryMutexMasterSlave

Using binary semaphore (same as Mutex) for 1 shared resource

thread-binary-semaphore

Using binary semaphore (same as Mutex) ticket seller for 1 shared resource (ticket counter) and 4 sellers

thread-binary-semaphore -ticketSeller

Using semaphore for reader/writer problem (1 writer & 2 readers) sharing 5 integer buffers

thread-semaphore-readerWriter