Transactional Memory
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Transactional Memory
In computer science and engineering, transactional memory attempts to simplify concurrent programming by allowing a group of load and store instructions to execute in an atomic way. It is a concurrency control mechanism analogous to database transactions for controlling access to shared memory in concurrent computing. Transactional memory systems provide high-level abstraction as an alternative to low-level thread synchronization. This abstraction allows for coordination between concurrent reads and writes of shared data in parallel systems. Motivation In concurrent programming, synchronization is required when parallel threads attempt to access a shared resource. Low-level thread synchronization constructs such as locks are pessimistic and prohibit threads that are outside a critical section from making any changes. The process of applying and releasing locks often functions as additional overhead in workloads with little conflict among threads. Transactional memory provides o ...
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Computer Science
Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to Applied science, practical disciplines (including the design and implementation of Computer architecture, hardware and Computer programming, software). Computer science is generally considered an area of research, academic research and distinct from computer programming. Algorithms and data structures are central to computer science. The theory of computation concerns abstract models of computation and general classes of computational problem, problems that can be solved using them. The fields of cryptography and computer security involve studying the means for secure communication and for preventing Vulnerability (computing), security vulnerabilities. Computer graphics (computer science), Computer graphics and computational geometry address the generation of images. Progr ...
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Hardware Transaction
Hardware may refer to: Technology Computing and electronics * Electronic hardware, interconnected electronic components which perform analog or logic operations ** Digital electronics, electronics that operate on digital signals *** Computer hardware, physical parts of a computer *** Networking hardware, devices that enable use of a computer network ** Electronic component, device in an electronic system used to affect electrons, usually industrial products Other technologies * Household hardware, equipment used for home repair and other work, such as fasteners, wire, plumbing supplies, electrical supplies, utensils, and machine parts *Builders hardware, metal hardware for building fixtures, such as hinges and latches * Hardware (development cooperation), in technology transfer * Drum hardware, used to tension, position, and support the instruments * Military technology, application of technology to warfare * Music hardware, devices other than instruments to create music Entertain ...
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Java (programming Language)
Java is a high-level, class-based, object-oriented programming language that is designed to have as few implementation dependencies as possible. It is a general-purpose programming language intended to let programmers ''write once, run anywhere'' ( WORA), meaning that compiled Java code can run on all platforms that support Java without the need to recompile. Java applications are typically compiled to bytecode that can run on any Java virtual machine (JVM) regardless of the underlying computer architecture. The syntax of Java is similar to C and C++, but has fewer low-level facilities than either of them. The Java runtime provides dynamic capabilities (such as reflection and runtime code modification) that are typically not available in traditional compiled languages. , Java was one of the most popular programming languages in use according to GitHub, particularly for client–server web applications, with a reported 9 million developers. Java was originally developed ...
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Speculative Multithreading
Thread Level Speculation (TLS), also known as Speculative Multithreading, or Speculative Parallelization, is a technique to speculatively execute a section of computer code that is anticipated to be executed later in parallel with the normal execution on a separate independent thread. Such a speculative thread may need to make assumptions about the values of input variables. If these prove to be invalid, then the portions of the speculative thread that rely on these input variables will need to be discarded and squashed. If the assumptions are correct the program can complete in a shorter time provided the thread was able to be scheduled efficiently. Description TLS extracts threads from serial code and executes them speculatively in parallel with a safe thread. The speculative thread will need to be discarded or re-run if its presumptions on the input state prove to be invalid. It is a dynamic (runtime) parallelization Parallel computing is a type of computation C ...
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Transmeta Efficeon
The Efficeon processor is Transmeta's second-generation 256-bit VLIW design released in 2004 which employs a software engine Code Morphing Software (CMS) to convert code written for x86 processors to the native instruction set of the chip. Like its predecessor, the Transmeta Crusoe (a 128-bit VLIW architecture), Efficeon stresses computational efficiency, low power consumption, and a low thermal footprint. Processor Efficeon most closely mirrors the feature set of Intel Pentium 4 processors, although, like AMD Opteron processors, it supports a fully integrated memory controller, a HyperTransport IO bus, and the NX bit, or no-execute x86 extension to PAE mode. NX bit support is available starting with CMS version 6.0.4. Efficeon's computational performance relative to mobile CPUs like the Intel Pentium M is thought to be lower, although little appears to be published about the relative performance of these competing processors. Efficeon came in two package types: a 783- and a ...
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Transmeta Crusoe
The Transmeta Crusoe is a family of x86-compatible microprocessors developed by Transmeta and introduced in 2000. Instead of the instruction set architecture being implemented in hardware, or translated by specialized hardware, the Crusoe runs a software abstraction layer, or a virtual machine, known as the Code Morphing Software (CMS). The CMS translates machine code instructions received from programs into native instructions for the microprocessor. In this way, the Crusoe can emulate other instruction set architectures (ISAs). This is used to allow the microprocessors to emulate the Intel x86 instruction set. OS and software limitations as of 2022 The Crusoe processor supports MMX but not SSE. As of 2022, most browsers on Windows and Linux, and some other programs, need SSE or SSE2 support; therefore, that software will no longer run on the Crusoe platform. For example, Firefox dropped support for systems without SSE2 long ago, although K-Meleon could run without SSE on ...
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Transmeta
Transmeta Corporation was an American fabless semiconductor company based in Santa Clara, California. It developed low power x86 compatible microprocessors based on a VLIW core and a software layer called Code Morphing Software. Code Morphing Software (CMS) consisted of an Interpreter (computing), interpreter, a runtime system and a Binary translation#Dynamic binary translation, dynamic binary translator. x86 instructions were first interpreted one instruction at a time and profiled, then depending upon the frequency of execution of a code block, CMS would progressively generate more optimized translations. The VLIW core implemented features specifically designed to accelerate CMS and translations. Among the features were support for general speculation, detection of memory aliasing and detection of self modifying x86 code. The combination of CMS and the VLIW core allowed for the achievement of full x86 compatibility while maintaining performance and reducing power consumption. ...
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Hardware Acceleration
Hardware acceleration is the use of computer hardware designed to perform specific functions more efficiently when compared to software running on a general-purpose central processing unit (CPU). Any transformation of data that can be calculated in software running on a generic CPU can also be calculated in custom-made hardware, or in some mix of both. To perform computing tasks more quickly (or better in some other way), generally one can invest time and money in improving the software, improving the hardware, or both. There are various approaches with advantages and disadvantages in terms of decreased latency, increased throughput and reduced energy consumption. Typical advantages of focusing on software may include more rapid development, lower non-recurring engineering costs, heightened portability, and ease of updating features or patching bugs, at the cost of overhead to compute general operations. Advantages of focusing on hardware may include speedup, reduced pow ...
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Compare And Swap
In computer science, compare-and-swap (CAS) is an atomic instruction used in multithreading to achieve synchronization. It compares the contents of a memory location with a given value and, only if they are the same, modifies the contents of that memory location to a new given value. This is done as a single atomic operation. The atomicity guarantees that the new value is calculated based on up-to-date information; if the value had been updated by another thread in the meantime, the write would fail. The result of the operation must indicate whether it performed the substitution; this can be done either with a simple boolean response (this variant is often called compare-and-set), or by returning the value read from the memory location (''not'' the value written to it). Overview A compare-and-swap operation is an atomic version of the following pseudocode, where denotes access through a pointer: function cas(p: pointer to int, old: int, new: int) is if *p ≠ old ...
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Runtime Library
In computer programming, a runtime library is a set of low-level routines used by a compiler to invoke some of the behaviors of a runtime environment, by inserting calls to the runtime library into compiled executable binary. The runtime environment implements the execution model, built-in functions, and other fundamental behaviors of a programming language. During execution (run time) of that computer program, execution of those calls to the runtime library cause communication between the executable binary and the runtime environment. A runtime library often includes built-in functions for memory management or exception handling. Therefore, a runtime library is always specific to the platform and compiler. The runtime library may implement a portion of the runtime environment's behavior, but if one reads the code of the calls available, they are typically only thin wrappers that simply package information, and send it to the runtime environment or operating system. However, ...
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Software Transactional Memory
In computer science, software transactional memory (STM) is a concurrency control mechanism analogous to database transactions for controlling access to shared memory in concurrent computing. It is an alternative to lock-based synchronization. STM is a strategy implemented in software, rather than as a hardware component. A transaction in this context occurs when a piece of code executes a series of reads and writes to shared memory. These reads and writes logically occur at a single instant in time; intermediate states are not visible to other (successful) transactions. The idea of providing hardware support for transactions originated in a 1986 paper by Tom Knight. The idea was popularized by Maurice Herlihy and J. Eliot B. Moss.Maurice Herlihy and J. Eliot B. Moss. ''Transactional memory: architectural support for lock-free data structures.'' Proceedings of the 20th annual international symposium on Computer architecture (ISCA '93). Volume 21, Issue 2, May 1993. In 1995 Nir Sh ...
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RISC
In computer engineering, a reduced instruction set computer (RISC) is a computer designed to simplify the individual instructions given to the computer to accomplish tasks. Compared to the instructions given to a complex instruction set computer (CISC), a RISC computer might require more instructions (more code) in order to accomplish a task because the individual instructions are written in simpler code. The goal is to offset the need to process more instructions by increasing the speed of each instruction, in particular by implementing an instruction pipeline, which may be simpler given simpler instructions. The key operational concept of the RISC computer is that each instruction performs only one function (e.g. copy a value from memory to a register). The RISC computer usually has many (16 or 32) high-speed, general-purpose registers with a load/store architecture in which the code for the register-register instructions (for performing arithmetic and tests) are separate fr ...
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