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#benchmarking#branchlessprogramming#branchprediction

New computers don't speed up old code

Matthias random stuff

255K subscribers • 1 video on Hallway

YouTube

Intermediate. Assumes working knowledge.

187K views1 year ago3 recommendations

Systems programmingHardwarePerformance and optimizationCPUs and computer architectureCompilers and interpreters

Matthias Wandel demonstrates how modern CPU bottlenecks like branch prediction and memory latency prevent unoptimized code from running faster on new hardware.

Testing old code on newer PCs and optimization techniques Including my newest, fastest PC, the Geekom IT13 Mini PC #geekom #geekomit13 #minipc #i913900HK Performance test program and data on github: github.com/Matthias-Wandel/perftests GEEKOM PC purchase links,6% Coupon Code: IT13MRSYT On GEEKOMs website: geekom.pxf.io/Qj0REP Amazon USA (32 meg + 1 ter SSD), $699 USD: pboost.me/lvi43ZJT Amazon USA (32 meg + 2 ter SSD), $749 USD: pboost.me/MuST1gc Amazon CA: amazon.ca/dp/B0DRJKNRYL?th=1

Why it's here

3 people recommend this

What people say. Recommended for showing how modern CPU architectures affect code performance and why branchless programming can help.

MontyCarloHallon Hacker News • Recommends

On “The Weird Concept of Branchless Programming”

…it's a lot more impressive than the measly 1.2x speedup highlighted in the article. I assume the minimal/nonexistent speedups in the article are due to modern CPU branch prediction being quite good. But branch predictors inherently fail miserably at CRC because the conditional is on whether the input bit is 1 or 0, which is essentially random. 0 link to this video…

dijiton Hacker News • Recommends

On “The world could run on older hardware if software optimization was a priority”

Maybe since 1980. I recently watched a video that can be summarised quite simply as: "Computers today aren't that much faster than the computers of 20 years ago, unless you specifically code for them". link to this video It's a little bit ham-fisted, as the author was shirking decades of compile optimisations also , and it's not apples to apples as he's comparing desktop class hardware with what is essentially laptop hardware; but it's also interesting to see that a lot of the performance gains really weren't that great actually. he observes a doubling of performance in 15 years! Truth be told most people use laptops now, and truth be told 20 years ago most people used desktops, so it's not totally unf…

torginuson Hacker News • Recommends

On “Uncle Sam shouldn't own Intel stock”

Watch this video: link to this video New computers aren't as much faster as benchmarks would lead you to believe. If your code relies on unpredictable branches, dependept memory accesses in a tight loop, or very tight feedback loops inside computations, new CPUs won't have that much of an edge.

scotty79on Hacker News • Mentions

On “The world could run on older hardware if software optimization was a priority”

Since 1980 maybe. But since 2005 it increased maybe 5x and even that's generous. And that's half of the time that passed and two decades. link to this video