Transactional memory originated in database theory, provides an alternative strategy for process synchronization.A memory transaction is atomic is a sequence of memory read–write operations. The memory transaction is committed, if all operations in a transaction are completed. Otherwise, the operations must be aborted and rolled back. The ease of transactional memory can be obtained through features added to a programming language. Consider an example. Suppose we have a function update() that modifies shared data. Traditionally, this function would be written using mutex locks (or semaphores) such as the following −void update (){    acquire(); /* modify shared data */   ... Read More

Solaris implements variety of locks to support multitasking, multithreading and multiprocessing. It uses adaptive mutexes, conditional variables, semaphores, read-write locks, turnstiles to control access to critical sections.An adaptive mutex uses for protecting every critical data item which are only accessed by short code segments.On A multiprocessor system it starts as a standard semaphore spin-lock. If the lock is held by a thread which is running on another CPU then the thread spins. If the lock is held by a thread which is currently in run state, the thread blocks, going to sleep until it is awakened by the signal of ... Read More

Windows operating system is a multithreaded kernel that provide support for real time application and multiprocessors. On uniprocessor system, Windows provides interrupt masks to protect access to global resources. It protects access to global resource using spinlock. The kernel uses spinlocks only to protect short code segment like Solaris. The kernel ensures that while holding a spinlock, a thread will never be preempted.Windows provide dispatcher object for thread synchronization according to several different mechanisms including mutexes, semaphores, events and timers. The system protects shared data by requiring a thread to gain ownership of a mutex for accessing the data and ... Read More

To implement monitor using semaphores, for each monitor, a semaphore mutex (which is initialized to 1) is provided. Wait(mutex) must be executed by a process before entering the monitor and must execute signal(mutex) after leaving the monitor. Since a signaling process must wait until the resumed process either leaves or waits, an additional semaphore, next, is introduced, initialized to 0. next can be used by The signaling processes to suspend themselves. An integer variable next_count is also provided to count the number of processes suspended on next. Thus, each external function F is replaced by-wait(mutex); … body of F ... ... Read More

Grand Central Dispatch (GCD) - a technology for Apple’s Mac OS X and iOS operating systems-is a combination of extensions to the C language, an API, and a run-time library that allows application developers to identify sections of code to run in parallel. Like OpenMP, GCD manages most of the details of threading. GCD identifies extensions to the C and C++ languages known as blocks. A block is simply a self-contained unit of work. It is specified by a caret ˆ inserted in front of a pair of braces { }. A simple example of a block is shown below ... Read More

OpenMP is a set of compiler directives as well as an API for programs written in C, C++, or FORTRAN that provides support for parallel programming in shared-memory environments. OpenMP identifies parallel regions as blocks of code that may run in parallel. Application developers insert compiler directives into their code at parallel regions, and these directives instruct the OpenMP run-time library to execute the region in parallel. The following C program illustrates a compiler directive above the parallel region containing the printf() statement −#include #include int main(int argc, char *argv[]){    /* sequential code */    #pragma omp ... Read More

Data ParallelismData Parallelism means concurrent execution of the same task on each multiple computing core.Let’s take an example, summing the contents of an array of size N. For a single-core system, one thread would simply sum the elements [0] . . . [N − 1]. For a dual-core system, however, thread A, running on core 0, could sum the elements [0] . . . [N/2 − 1] and while thread B, running on core 1, could sum the elements [N/2] . . . [N − 1]. So the Two threads would be running in parallel on separate computing cores.Task ParallelismTask ... Read More

Data ParallelismData Parallelism means concurrent execution of the same task on each multiple computing core.Let’s take an example, summing the contents of an array of size N. For a single-core system, one thread would simply sum the elements [0] . . . [N − 1]. For a dual-core system, however, thread A, running on core 0, could sum the elements [0] . . . [N/2 − 1] and while thread B, running on core 1, could sum the elements [N/2] . . . [N − 1]. So the Two threads would be running in parallel on separate computing cores.Task ParallelismTask ... Read More

Amdahl’s LawSuppose, Moni have to attend an invitation. Moni’s another two friend Diya and Hena are also invited. There are conditions that all three friends have to go there separately and all of them have to be present at door to get into the hall. Now Moni is coming by car, Diya by bus and Hena is coming by foot. Now, how fast Moni and Diya can reach there it doesn’t matter, they have to wait for Hena. So to speed up the overall process, we need to concentrate on the performance of Hena other than Moni or Diya.This is ... Read More

Multicore programming helps to create concurrent systems for deployment on multicore processor and multiprocessor systems. A multicore processor system is basically a single processor with multiple execution cores in one chip. It has multiple processors on the motherboard or chip. A Field-Programmable Gate Array (FPGA) is might be included in a multiprocessor system. A FPGA is an integrated circuit containing an array of programmable logic blocks and a hierarchy of reconfigurable interconnects. Input data is processed by to produce outputs. It can be a processor in a multicore or multiprocessor system, or a FPGA.The multicore programming approach has following advantages ... Read More