Why is this C++ code faster than my hand-written assembly (2016)

Re:Why is this C++ code faster than my hand-written assembly... by ryandrake on Tuesday August 22, 2017 @03:19PM (#15075536)

I don't know--it just seems like we have lost something as a profession. Lost some of the craft and efficiency. I get that this is a practical attitude and often the right answer. But always working with "managed" languages and moving higher and higher up in the abstractions is one of the reasons we now need clusters of computers to solve problems. We've gone from computers the size of rooms to personal computers that can rest on your lap, all the way back to racks of computers that need an entire room.

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Re:Why is this C++ code faster than my hand-written assembly... by pcordes on Thursday August 24, 2017 @01:18PM (#15092021)

Actual high-performance-computing clusters are typically used efficiently, running well-tuned code. BLAS libraries (matrix multiplication) are usually very heavily optimized.

Of course, a lot of code just uses these optimized building blocks and ends up doing multiple passes over the data instead of doing more with each pass while it's still hot in cache. It's disappointing that we still don't have optimizing compilers that know how to produce code for an efficient matrix multiply or something, and be able to mix in some other work right into that.

Your point definitely applies to server farms, though, running a huge stack of interpreted languages and big clunky "building blocks" instead of something written efficiently.

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Re:Why is this C++ code faster than my hand-written assembly... by pjmlp on Tuesday August 22, 2017 @04:00PM (#15075856)

I see it a bit differently.

Developers using Lisp during the 60's all the way to Lisp Machines in the 80's would jump of joy if they could get their hands on a RaspberryPI level hardware.

So the capabilities are there, but it is up to the developers to actually make use of them.

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Re:Why is this C++ code faster than my hand-written assembly... by pjmlp on Wednesday August 23, 2017 @02:06AM (#15078903)

As addendum to my previous comment, managed languages have always been a thing outside AT&T.

It was Bjarne's disappointment with BCPL after tasting the productivity of Simula, that made him design C++ as his way to avoid using plain C.

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