據日前在多核大會(Multicore Expo)期間召開的一個專家討論會，多核編程日益接近其極限。如果沒有新的工具與方法，程序員將無法繼續(xù)發(fā)揮并行程度越來越高的未來芯片的潛力。 處理器設計者不再追求高頻率，而是采取多核設計，以避免硬件的功率泄漏（power leakage）問題。但這使得更加有必要采用并行編程工具和方法，但這些東西目前并不存在。 “目前我們面對一堵墻，”諾基亞西門子通信首席設計師Alex Bachmutsky表示，“如果沒有多核處理器，可能不會再有更多的產品出現，(但)我們在并行編程方面遇到許多問題?！? Bachmutsky指出：“其中的一個問題是，如何使長達800萬或1000萬行的現有程序變成并行程序。當然，你可以全部重寫，但這將耗費大量資金?！? “另一個問題是，我們有些算法從定義來說不是并行的，如Viterbi譯碼算法，”他說，“我們可以改變這個算法，但我們?yōu)榇吮仨毟淖內炕竞褪謾C，而這并不可行?！? 一位聽眾注意到另一個迫近的問題：開發(fā)者不能再期望下一代處理器會提升其應用程序的效能。他說：“40年來我們一直在吃免費的午餐，但是現在，我不知道我今天所寫的程序能否在20年后仍然可用?！? LSI的杰出工程師Rob Munoz表示：“你可以把內核數量增加一倍，但實際上會降低性能?！? “并行軟件難以開發(fā)、維護和發(fā)展，”Munoz表示，“大量嘗試過的公司都倒下了，但產業(yè)仍堅持多核方式，因為它是進一步縮小芯片尺寸的唯一途徑?！? 他說，對于通訊芯片，LSI在使用多核方面采取了一種保守方式，以限制軟件問題。 咨詢公司The PTR Group的首席科學家Mike Anderson表示：“我們試圖解決的大量問題，都是30年來在高性能計算方面的問題，我們尚未解決。”他說，一個棘手問題是如何管理多線程應用，在這些應用中，線程可能在不同的內核之間移動。 “必須改變思考這個問題的方式，”Anderson表示，“搞DSP的人知道，乘/加和快速傅立葉變換這樣的并行任務如何工作，但這些人目前在市場中并不是多數?！? 在被問及產業(yè)是否需要新的編程語言時，一位專家表示，我們已經擁有太多的語言。他說：“首先需要理解它對于并行有什么意義。” 版權聲明：本文授權轉載自www.eetimes.com，謝絕轉載！

相關閱讀：
• 評論：為什么ARM與AMD合作有意義？
• 多核處理器將是汽車電子的基本選擇
• Hypervisor虛擬化技術掃清多核嵌入式市場開發(fā)障礙I09esmc

下一頁：查看英文原文：Panel: Wall ahead in multicore programming {pagination} Panel: Wall ahead in multicore programming Rick Merritt SAN JOSE, Calif. – The wall on the horizon in multicore programming is getting closer, according to a panel of experts at the Multicore Expo here. Without new tools and methods, programmers will not be able to continue to reap significant benefits from tomorrow's increasingly parallel chips. Processor designers switched from pushing frequency to delivering multicore designs to avoid hardware problems of power leakage. But that has created an increasingly pressing need for parallel programming tools and methods that don't yet exist. "The wall is there," said Alex Bachmutsky, a chief architect at Nokia Siemens Networks. "We probably won't have any more products without multicore processors [but] we see a lot of problems in parallel programming," he said. "One of our problems is how to parallelize existing programs with eight or 10 million lines of code--you can rewrite everything but it will cost a lot of money," Bachmutsky said. "The other problem is we have some algorithms that from their definition were not parallel like Viterbi decoding," he said. "We can change it, but we'd have to change all the cell towers and phones, too, and it's not do-able," he added. An audience member noted another looming problem: developers can no longer expect next-generation processors will boost performance of their apps. "For 40 years we got a free lunch, but now I wonder what I can write in my code today that will still work in 20 years," he said. "You can double cores and actually decrease performance," said Rob Munoz, a distinguished engineer at LSI. "Parallel software is hard to develop, maintain and evolve," Munoz said. "There's a graveyard of companies who have tried, but the industry is stuck with multicore because it’s the only way to scale chips," he said. LSI has taken a conservative approach to using multicore in its comms chips to limit the software problems, he said. "A lot of the problems we are trying to address are ones we have had for 30 years in high performance computing, and we haven't solved them yet," said Mike Anderson, chief scientist, with The PTR Group, a consulting firm. One nasty problem is how to manage multithreaded apps where threads may move between different cores, he said. "You have to change the way you think about the problem," Anderson said. "People in DSP understand how parallel tasks such as multiply-accumulates and fast Fourier Transforms work, but that’s not the majority of developers in the market now," he said. Asked if the industry needs a new programming language, one panelist said we already have too many of them. "First need to understand what it means to be parallel," he said.