- Timestamp:
- Jun 24, 2019, 5:00:47 PM (5 years ago)
- Branches:
- ADT, arm-eh, ast-experimental, enum, forall-pointer-decay, jacob/cs343-translation, jenkins-sandbox, master, new-ast, new-ast-unique-expr, pthread-emulation, qualifiedEnum
- Children:
- 28564382
- Parents:
- 1335e6f
- Location:
- doc
- Files:
-
- 2 edited
Legend:
- Unmodified
- Added
- Removed
-
doc/bibliography/pl.bib
r1335e6f r64dc36e 954 954 key = {Cforall Benchmarks}, 955 955 author = {{\textsf{C}{$\mathbf{\forall}$} Benchmarks}}, 956 howpublished= {\href{https://plg.uwaterloo.ca/~cforall/benchmark s}{https://\-plg.uwaterloo.ca/\-$\sim$cforall/\-benchmarks}},956 howpublished= {\href{https://plg.uwaterloo.ca/~cforall/benchmark.tar}{https://\-plg.uwaterloo.ca/\-$\sim$cforall/\-benchmark.tar}}, 957 957 } 958 958 -
doc/papers/concurrency/Paper.tex
r1335e6f r64dc36e 316 316 Finally, performant user-threading implementations (both time and space) meet or exceed direct kernel-threading implementations, while achieving the programming advantages of high concurrency levels and safety. 317 317 318 A further effort over the past two decades is the development of language memory models to deal with the conflict between language features and compiler/hardware optimizations, \ie ,some language features are unsafe in the presence of aggressive sequential optimizations~\cite{Buhr95a,Boehm05}.318 A further effort over the past two decades is the development of language memory models to deal with the conflict between language features and compiler/hardware optimizations, \ie some language features are unsafe in the presence of aggressive sequential optimizations~\cite{Buhr95a,Boehm05}. 319 319 The consequence is that a language must provide sufficient tools to program around safety issues, as inline and library code is all sequential to the compiler. 320 One solution is low-level qualifiers and functions (\eg ,@volatile@ and atomics) allowing \emph{programmers} to explicitly write safe (race-free~\cite{Boehm12}) programs.320 One solution is low-level qualifiers and functions (\eg @volatile@ and atomics) allowing \emph{programmers} to explicitly write safe (race-free~\cite{Boehm12}) programs. 321 321 A safer solution is high-level language constructs so the \emph{compiler} knows the optimization boundaries, and hence, provides implicit safety. 322 322 This problem is best known with respect to concurrency, but applies to other complex control-flow, like exceptions\footnote{ … … 324 324 The key feature that dovetails with this paper is nonlocal exceptions allowing exceptions to be raised across stacks, with synchronous exceptions raised among coroutines and asynchronous exceptions raised among threads, similar to that in \uC~\cite[\S~5]{uC++} 325 325 } and coroutines. 326 Finally, language solutions allow matching constructs with language paradigm, \ie ,imperative and functional languages often have different presentations of the same concept to fit their programming model.326 Finally, language solutions allow matching constructs with language paradigm, \ie imperative and functional languages often have different presentations of the same concept to fit their programming model. 327 327 328 328 Finally, it is important for a language to provide safety over performance \emph{as the default}, allowing careful reduction of safety for performance when necessary. 329 Two concurrency violations of this philosophy are \emph{spurious wakeup} (random wakeup~\cite[\S~8]{Buhr05a}) and \emph{barging} (signals-as-hints~\cite[\S~8]{Buhr05a}), where one is a consequence of the other, \ie ,once there is spurious wakeup, signals-as-hints follow.329 Two concurrency violations of this philosophy are \emph{spurious wakeup} (random wakeup~\cite[\S~8]{Buhr05a}) and \emph{barging} (signals-as-hints~\cite[\S~8]{Buhr05a}), where one is a consequence of the other, \ie once there is spurious wakeup, signals-as-hints follow. 330 330 However, spurious wakeup is \emph{not} a foundational concurrency property~\cite[\S~8]{Buhr05a}, it is a performance design choice. 331 331 Similarly, signals-as-hints are often a performance decision. … … 337 337 Most augmented traditional (Fortran 18~\cite{Fortran18}, Cobol 14~\cite{Cobol14}, Ada 12~\cite{Ada12}, Java 11~\cite{Java11}) and new languages (Go~\cite{Go}, Rust~\cite{Rust}, and D~\cite{D}), except \CC, diverge from C with different syntax and semantics, only interoperate indirectly with C, and are not systems languages, for those with managed memory. 338 338 As a result, there is a significant learning curve to move to these languages, and C legacy-code must be rewritten. 339 While \CC, like \CFA, takes an evolutionary approach to extend C, \CC's constantly growing complex and interdependent features-set (\eg ,objects, inheritance, templates, etc.) mean idiomatic \CC code is difficult to use from C, and C programmers must expend significant effort learning \CC.339 While \CC, like \CFA, takes an evolutionary approach to extend C, \CC's constantly growing complex and interdependent features-set (\eg objects, inheritance, templates, etc.) mean idiomatic \CC code is difficult to use from C, and C programmers must expend significant effort learning \CC. 340 340 Hence, rewriting and retraining costs for these languages, even \CC, are prohibitive for companies with a large C software-base. 341 341 \CFA with its orthogonal feature-set, its high-performance runtime, and direct access to all existing C libraries circumvents these problems. … … 367 367 \section{Stateful Function} 368 368 369 The stateful function is an old idea~\cite{Conway63,Marlin80} that is new again~\cite{C++20Coroutine19}, where execution is temporarily suspended and later resumed, \eg ,plugin, device driver, finite-state machine.369 The stateful function is an old idea~\cite{Conway63,Marlin80} that is new again~\cite{C++20Coroutine19}, where execution is temporarily suspended and later resumed, \eg plugin, device driver, finite-state machine. 370 370 Hence, a stateful function may not end when it returns to its caller, allowing it to be restarted with the data and execution location present at the point of suspension. 371 371 This capability is accomplished by retaining a data/execution \emph{closure} between invocations. 372 If the closure is fixed size, we call it a \emph{generator} (or \emph{stackless}), and its control flow is restricted, \eg ,suspending outside the generator is prohibited.373 If the closure is variabl y sized, we call it a \emph{coroutine} (or \emph{stackful}), and as the names implies, often implemented with a separate stack with no programming restrictions.372 If the closure is fixed size, we call it a \emph{generator} (or \emph{stackless}), and its control flow is restricted, \eg suspending outside the generator is prohibited. 373 If the closure is variable size, we call it a \emph{coroutine} (or \emph{stackful}), and as the names implies, often implemented with a separate stack with no programming restrictions. 374 374 Hence, refactoring a stackless coroutine may require changing it to stackful. 375 A foundational property of all \emph{stateful functions} is that resume/suspend \emph{do not} cause incremental stack growth, \ie ,resume/suspend operations are remembered through the closure not the stack.375 A foundational property of all \emph{stateful functions} is that resume/suspend \emph{do not} cause incremental stack growth, \ie resume/suspend operations are remembered through the closure not the stack. 376 376 As well, activating a stateful function is \emph{asymmetric} or \emph{symmetric}, identified by resume/suspend (no cycles) and resume/resume (cycles). 377 377 A fixed closure activated by modified call/return is faster than a variable closure activated by context switching. 378 Additionally, any storage management for the closure (especially in unmanaged languages, \ie ,no garbage collection) must also be factored into design and performance.378 Additionally, any storage management for the closure (especially in unmanaged languages, \ie no garbage collection) must also be factored into design and performance. 379 379 Therefore, selecting between stackless and stackful semantics is a tradeoff between programming requirements and performance, where stackless is faster and stackful is more general. 380 380 Note, creation cost is amortized across usage, so activation cost is usually the dominant factor. … … 648 648 \end{center} 649 649 The example takes advantage of resuming a generator in the constructor to prime the loops so the first character sent for formatting appears inside the nested loops. 650 The destructor provides a newline if formatted text ends with a full line.650 The destructor provides a newline, if formatted text ends with a full line. 651 651 Figure~\ref{f:CFormatSim} shows the C implementation of the \CFA input generator with one additional field and the computed @goto@. 652 652 For contrast, Figure~\ref{f:PythonFormatter} shows the equivalent Python format generator with the same properties as the Fibonacci generator. … … 2719 2719 Each benchmark experiment is run 31 times. 2720 2720 All omitted tests for other languages are functionally identical to the \CFA tests and available online~\cite{CforallBenchMarks}. 2721 2721 % tar --exclude=.deps --exclude=Makefile --exclude=Makefile.in --exclude=c.c --exclude=cxx.cpp --exclude=fetch_add.c -cvhf benchmark.tar benchmark 2722 2722 2723 2723 \paragraph{Object Creation} … … 2749 2749 \multicolumn{1}{@{}c}{} & \multicolumn{1}{c}{Median} & \multicolumn{1}{c}{Average} & \multicolumn{1}{c@{}}{Std Dev} \\ 2750 2750 \CFA Coroutine Lazy & 14.3 & 14.3 & 0.32 \\ 2751 \CFA Coroutine Eager & 2203.7 & 2205.6 & 26.03\\2751 \CFA Coroutine Eager & 522.8 & 525.3 & 5.81 \\ 2752 2752 \CFA Thread & 1257.8 & 1291.2 & 86.19 \\ 2753 2753 \uC Coroutine & 92.2 & 91.4 & 1.58 \\
Note: See TracChangeset
for help on using the changeset viewer.