CS110 Lecture 10: Threads and Mutexes
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Palmetto Tatters Guild Glossary of Tatting Terms (Not All Inclusive!)
Palmetto Tatters Guild Glossary of Tatting Terms (not all inclusive!) Tat Days Written * or or To denote repeating lines of a pattern. Example: Rep directions or # or § from * 7 times & ( ) Eg. R: 5 + 5 – 5 – 5 (last P of prev R). Modern B Bead (Also see other bead notation below) notation BTS Bare Thread Space B or +B Put bead on picot before joining BBB B or BBB|B Three beads on knotting thread, and one bead on core thread Ch Chain ^ Construction picot or very small picot CTM Continuous Thread Method D Dimple: i.e. 1st Half Double Stitch X4, 2nd Half Double Stitch X4 dds or { } daisy double stitch DNRW DO NOT Reverse Work DS Double Stitch DP Down Picot: 2 of 1st HS, P, 2 of 2nd HS DPB Down Picot with a Bead: 2 of 1st HS, B, 2 of 2nd HS HMSR Half Moon Split Ring: Fold the second half of the Split Ring inward before closing so that the second side and first side arch in the same direction HR Half Ring: A ring which is only partially closed, so it looks like half of a ring 1st HS First Half of Double Stitch 2nd HS Second Half of Double Stitch JK Josephine Knot (Ring made of only the 1st Half of Double Stitch OR only the 2nd Half of Double Stitch) LJ or Sh+ or SLJ Lock Join or Shuttle join or Shuttle Lock Join LPPCh Last Picot of Previous Chain LPPR Last Picot of Previous Ring LS Lock Stitch: First Half of DS is NOT flipped, Second Half is flipped, as usual LCh Make a series of Lock Stitches to form a Lock Chain MP or FP Mock Picot or False Picot MR Maltese Ring Pearl Ch Chain made with pearl tatting technique (picots on both sides of the chain, made using three threads) P or - Picot Page 1 of 4 PLJ or ‘PULLED LOOP’ join or ‘PULLED LOCK’ join since it is actually a lock join made after placing thread under a finished ring and pulling this thread through a picot. -
Logix 5000 Controllers Security, 1756-PM016O-EN-P
Logix 5000 Controllers Security 1756 ControlLogix, 1756 GuardLogix, 1769 CompactLogix, 1769 Compact GuardLogix, 1789 SoftLogix, 5069 CompactLogix, 5069 Compact GuardLogix, Studio 5000 Logix Emulate Programming Manual Original Instructions Logix 5000 Controllers Security Important User Information Read this document and the documents listed in the additional resources section about installation, configuration, and operation of this equipment before you install, configure, operate, or maintain this product. Users are required to familiarize themselves with installation and wiring instructions in addition to requirements of all applicable codes, laws, and standards. Activities including installation, adjustments, putting into service, use, assembly, disassembly, and maintenance are required to be carried out by suitably trained personnel in accordance with applicable code of practice. If this equipment is used in a manner not specified by the manufacturer, the protection provided by the equipment may be impaired. In no event will Rockwell Automation, Inc. be responsible or liable for indirect or consequential damages resulting from the use or application of this equipment. The examples and diagrams in this manual are included solely for illustrative purposes. Because of the many variables and requirements associated with any particular installation, Rockwell Automation, Inc. cannot assume responsibility or liability for actual use based on the examples and diagrams. No patent liability is assumed by Rockwell Automation, Inc. with respect to use of information, circuits, equipment, or software described in this manual. Reproduction of the contents of this manual, in whole or in part, without written permission of Rockwell Automation, Inc., is prohibited. Throughout this manual, when necessary, we use notes to make you aware of safety considerations. -
Multithreading Design Patterns and Thread-Safe Data Structures
Lecture 12: Multithreading Design Patterns and Thread-Safe Data Structures Principles of Computer Systems Autumn 2019 Stanford University Computer Science Department Lecturer: Chris Gregg Philip Levis PDF of this presentation 1 Review from Last Week We now have three distinct ways to coordinate between threads: mutex: mutual exclusion (lock), used to enforce critical sections and atomicity condition_variable: way for threads to coordinate and signal when a variable has changed (integrates a lock for the variable) semaphore: a generalization of a lock, where there can be n threads operating in parallel (a lock is a semaphore with n=1) 2 Mutual Exclusion (mutex) A mutex is a simple lock that is shared between threads, used to protect critical regions of code or shared data structures. mutex m; mutex.lock() mutex.unlock() A mutex is often called a lock: the terms are mostly interchangeable When a thread attempts to lock a mutex: Currently unlocked: the thread takes the lock, and continues executing Currently locked: the thread blocks until the lock is released by the current lock- holder, at which point it attempts to take the lock again (and could compete with other waiting threads). Only the current lock-holder is allowed to unlock a mutex Deadlock can occur when threads form a circular wait on mutexes (e.g. dining philosophers) Places we've seen an operating system use mutexes for us: All file system operation (what if two programs try to write at the same time? create the same file?) Process table (what if two programs call fork() at the same time?) 3 lock_guard<mutex> The lock_guard<mutex> is very simple: it obtains the lock in its constructor, and releases the lock in its destructor. -
Lecture 4 Resource Protection and Thread Safety
Concurrency and Correctness – Resource Protection and TS Lecture 4 Resource Protection and Thread Safety 1 Danilo Piparo – CERN, EP-SFT Concurrency and Correctness – Resource Protection and TS This Lecture The Goals: 1) Understand the problem of contention of resources within a parallel application 2) Become familiar with the design principles and techniques to cope with it 3) Appreciate the advantage of non-blocking techniques The outline: § Threads and data races: synchronisation issues § Useful design principles § Replication, atomics, transactions and locks § Higher level concrete solutions 2 Danilo Piparo – CERN, EP-SFT Concurrency and Correctness – Resource Protection and TS Threads and Data Races: Synchronisation Issues 3 Danilo Piparo – CERN, EP-SFT Concurrency and Correctness – Resource Protection and TS The Problem § Fastest way to share data: access the same memory region § One of the advantages of threads § Parallel memory access: delicate issue - race conditions § I.e. behaviour of the system depends on the sequence of events which are intrinsically asynchronous § Consequences, in order of increasing severity § Catastrophic terminations: segfaults, crashes § Non-reproducible, intermittent bugs § Apparently sane execution but data corruption: e.g. wrong value of a variable or of a result Operative definition: An entity which cannot run w/o issues linked to parallel execution is said to be thread-unsafe (the contrary is thread-safe) 4 Danilo Piparo – CERN, EP-SFT Concurrency and Correctness – Resource Protection and TS To Be Precise: Data Race Standard language rules, §1.10/4 and /21: • Two expression evaluations conflict if one of them modifies a memory location (1.7) and the other one accesses or modifies the same memory location. -
Clojure, Given the Pun on Closure, Representing Anything Specific
dynamic, functional programming for the JVM “It (the logo) was designed by my brother, Tom Hickey. “It I wanted to involve c (c#), l (lisp) and j (java). I don't think we ever really discussed the colors Once I came up with Clojure, given the pun on closure, representing anything specific. I always vaguely the available domains and vast emptiness of the thought of them as earth and sky.” - Rich Hickey googlespace, it was an easy decision..” - Rich Hickey Mark Volkmann [email protected] Functional Programming (FP) In the spirit of saying OO is is ... encapsulation, inheritance and polymorphism ... • Pure Functions • produce results that only depend on inputs, not any global state • do not have side effects such as Real applications need some changing global state, file I/O or database updates side effects, but they should be clearly identified and isolated. • First Class Functions • can be held in variables • can be passed to and returned from other functions • Higher Order Functions • functions that do one or both of these: • accept other functions as arguments and execute them zero or more times • return another function 2 ... FP is ... Closures • main use is to pass • special functions that retain access to variables a block of code that were in their scope when the closure was created to a function • Partial Application • ability to create new functions from existing ones that take fewer arguments • Currying • transforming a function of n arguments into a chain of n one argument functions • Continuations ability to save execution state and return to it later think browser • back button 3 .. -
Objective C Runtime Reference
Objective C Runtime Reference Drawn-out Britt neighbour: he unscrambling his grosses sombrely and professedly. Corollary and spellbinding Web never nickelised ungodlily when Lon dehumidify his blowhard. Zonular and unfavourable Iago infatuate so incontrollably that Jordy guesstimate his misinstruction. Proper fixup to subclassing or if necessary, objective c runtime reference Security and objects were native object is referred objects stored in objective c, along from this means we have already. Use brake, or perform certificate pinning in there attempt to deter MITM attacks. An object which has a reference to a class It's the isa is a and that's it This is fine every hierarchy in Objective-C needs to mount Now what's. Use direct access control the man page. This function allows us to voluntary a reference on every self object. The exception handling code uses a header file implementing the generic parts of the Itanium EH ABI. If the method is almost in the cache, thanks to Medium Members. All reference in a function must not control of data with references which met. Understanding the Objective-C Runtime Logo Table Of Contents. Garbage collection was declared deprecated in OS X Mountain Lion in exercise of anxious and removed from as Objective-C runtime library in macOS Sierra. Objective-C Runtime Reference. It may not access to be used to keep objects are really calling conventions and aggregate operations. Thank has for putting so in effort than your posts. This will cut down on the alien of Objective C runtime information. Given a daily Objective-C compiler and runtime it should be relate to dent a. -
Lock Free Data Structures Using STM in Haskell
Lock Free Data Structures using STM in Haskell Anthony Discolo1, Tim Harris2, Simon Marlow2, Simon Peyton Jones2, Satnam Singh1 1 Microsoft, One Microsoft Way, Redmond, WA 98052, USA {adiscolo, satnams}@microsoft.com http://www.research.microsoft.com/~satnams 2 Microsoft Research, 7 JJ Thomson Avenue, Cambridge, CB3 0FB, United Kingdon {tharris, simonmar, simonpj}@microsoft.com Abstract. This paper explores the feasibility of re-expressing concurrent algo- rithms with explicit locks in terms of lock free code written using Haskell’s im- plementation of software transactional memory. Experimental results are pre- sented which show that for multi-processor systems the simpler lock free im- plementations offer superior performance when compared to their correspond- ing lock based implementations. 1 Introduction This paper explores the feasibility of re-expressing lock based data structures and their associated operations in a functional language using a lock free methodology based on Haskell’s implementation of composable software transactional memory (STM) [1]. Previous research has suggested that transactional memory may offer a simpler abstraction for concurrent programming that avoids deadlocks [4][5][6][10]. Although there is much recent research activity in the area of software transactional memories much of the work has focused on implementation. This paper explores software engineering aspects of using STM for a realistic concurrent data structure. Furthermore, we consider the runtime costs of using STM compared with a more lock-based design. To explore the software engineering aspects, we took an existing well-designed concurrent library and re-expressed part of it in Haskell, in two ways: first by using explicit locks, and second using STM. -
Developing with Pojos: Faster and Easier 3 Chapter 2 ■ J2EE Design Decisions 31
FROM OUR PEER REVIEW ... “Chris Richardson targets critical design issues for lightweight Java enterprise applications using POJOs with fantastic in-depth exam- ples. This book extends Martin Fowler’s great book, Enterprise Architecture Patterns, as well as the more recent Domain-Driven Design by Eric Evans, by providing practical design guidance and useful examples. It also addresses the architecture and design issues asso- ciated with Spring and Hibernate development, whereas Man- ning’s companion ‘in Action’ books focus primarily on the Spring and Hibernate technologies. “This is a powerful book for architects, senior developers, and consultants. It uniquely combines best practices and design wisdom to integrate domain-driven design and test-driven development for object-oriented Java enterprise applications using lightweight Spring, Hibernate, and JDO technologies. “The table of contents reflects the important topics that most architects and enterprise developers face every day. There is signifi- cant need for a book like this, which shows how to address many common and complex design issues with real-world examples. The content in this book is unique and not really available elsewhere.” DOUG WARREN Software Architect Countrywide Financial “POJOs in Action fills a void: the need for a practical explanation of the techniques used at various levels for the successful building of J2EE projects. This book can be compared with the less enterprise- oriented and more abstract J2EE Development without EJB by Rod Johnson, but Richardson offers a step-by-step guide to a successful J2EE project. The explanations of the various alternatives available for each step provide the main thrust of this book. -
Java Concurrency in Practice
Java Concurrency in practice Chapters: 1,2, 3 & 4 Bjørn Christian Sebak ([email protected]) Karianne Berg ([email protected]) INF329 – Spring 2007 Chapter 1 - Introduction Brief history of concurrency Before OS, a computer executed a single program from start to finnish But running a single program at a time is an inefficient use of computer hardware Therefore all modern OS run multiple programs (in seperate processes) Brief history of concurrency (2) Factors for running multiple processes: Resource utilization: While one program waits for I/O, why not let another program run and avoid wasting CPU cycles? Fairness: Multiple users/programs might have equal claim of the computers resources. Avoid having single large programs „hog“ the machine. Convenience: Often desirable to create smaller programs that perform a single task (and coordinate them), than to have one large program that do ALL the tasks What is a thread? A „lightweight process“ - each process can have many threads Threads allow multiple streams of program flow to coexits in a single process. While a thread share process-wide resources like memory and files with other threads, they all have their own program counter, stack and local variables Benefits of threads 1) Exploiting multiple processors 2) Simplicity of modeling 3) Simplified handling of asynchronous events 4) More responsive user interfaces Benefits of threads (2) Exploiting multiple processors The processor industry is currently focusing on increasing number of cores on a single CPU rather than increasing clock speed. Well-designed programs with multiple threads can execute simultaneously on multiple processors, increasing resource utilization. -
Lock-Free Programming
Lock-Free Programming Geoff Langdale L31_Lockfree 1 Desynchronization ● This is an interesting topic ● This will (may?) become even more relevant with near ubiquitous multi-processing ● Still: please don’t rewrite any Project 3s! L31_Lockfree 2 Synchronization ● We received notification via the web form that one group has passed the P3/P4 test suite. Congratulations! ● We will be releasing a version of the fork-wait bomb which doesn't make as many assumptions about task id's. – Please look for it today and let us know right away if it causes any trouble for you. ● Personal and group disk quotas have been grown in order to reduce the number of people running out over the weekend – if you try hard enough you'll still be able to do it. L31_Lockfree 3 Outline ● Problems with locking ● Definition of Lock-free programming ● Examples of Lock-free programming ● Linux OS uses of Lock-free data structures ● Miscellanea (higher-level constructs, ‘wait-freedom’) ● Conclusion L31_Lockfree 4 Problems with Locking ● This list is more or less contentious, not equally relevant to all locking situations: – Deadlock – Priority Inversion – Convoying – “Async-signal-safety” – Kill-tolerant availability – Pre-emption tolerance – Overall performance L31_Lockfree 5 Problems with Locking 2 ● Deadlock – Processes that cannot proceed because they are waiting for resources that are held by processes that are waiting for… ● Priority inversion – Low-priority processes hold a lock required by a higher- priority process – Priority inheritance a possible solution L31_Lockfree -
Scalable Join Patterns
Scalable Join Patterns Claudio Russo Microsoft Research Joint work with Aaron Turon (Northeastern). Outline Join patterns Examples Implementation Optimizations Evaluation Conclusion Outline Join patterns Examples Implementation Optimizations Evaluation Conclusion Background Parallel programs eventually need to synchronize. I Writing correct synchronization code is hard. I Writing efficient synchronization code is harder still. Neglect efficiency and promised performance gains are easily eroded … …by the cost of synchronization! Can we make this easier for programmers? Goal Our Goal: I provide scalable, parallel synchronization I using declarative, high-level abstractions Our Recipe: 1. Take our favourite concurrency model: Join Calculus [Fournet & Gonthier] 2. Give it a scalable, parallel implementation. Join Calculus in a nutshell A basic calculus for message passing concurrency. Like π-calculus, but with a twist…. Definitions can declare synchronous and asynchronous channels. Threads communicate and synchronize by sending messages: I a synchronous send waits until the channel returns some result; I an asynchronous send returns immediately, posting a message. Chords Definitions contains collections of chords (a.k.a. join patterns). A chord pairs a pattern over channels with a continuation. The continuation may run when these channels are filled. Each send may enable: some pattern causing a request to complete or a new thread to run; no pattern causing the request to block or the message to queue. All messages in a pattern are consumed in one atomic step. Example§ (C#) ¤ Asynchronous.Channel Knife, Fork; // () -> void ¦Synchronous.Channel Hungry, SpoonFeed; // () -> void ¥ Calling Hungry() waits until the channel returns control (a request). Calling Knife(); returns immediately, but posts a resource. §Chords specify alternative reactions to messages. -
Object Oriented Paradigm/Programming
an object is an instantiation from a class, e.g., you have a pet cat, who's Object Oriented Paradigm name is Garfield, then Garfield is a object (of the class cat) to invoke an method, simply do obj.method( ) or obj->method( ), the Ming- Hwa Wang, Ph.D. former is object reference syntax, and the latter is pointer syntax Department of Computer Engineering Santa Clara University Relationships a-kind-of relationship: a subclass inherits and adds more attributes Object Oriented Paradigm/Programming (OOP) and/or methods from its super class to become somewhat "specialized" similar to Lego, which kids build new toys from assembling the existing is-a relationship: an object of a subclass is an object of its super class construction blocks of different shapes part-of relationship: OOP - doing programs by reusing (composing/inheriting) objects has-a relationship: (instantiated from classes) as much as possible, and only writing code when no exiting objects can be applied Reusability inheritance Two Fundamental Principles for OOP a sub/child/derived/extended class can inherit all properties from its generalization or reusability: the classes designed should target to super/parent/base/original class, with or without reusability, i.e., it should very generic and can be applied to lots of modification/override or addition situations/applications without much efforts; reusability comes from single inheritance and multiple inheritance (watch out naming inheritance and/or composition conflicts) encapsulation or information hiding: we can hide detailed or composition implementation specific information away from the users/programmers, so changing implementation using the same interfaces will not need Abstract or Virtual Classes modifying the application code only used as a super class for other classes, only specified but not fully defined, and can't be instantiated OOP Language vs.