For anyone interested in C++ compiler differences, the 'Compiler Explorer' ( http://www.godbolt.org ) is an indispensable resource.
Basically, you can write some code, select some different compilers (and optimization flags), and look at the assembly code and compare windows side-by-side. I used to have a bunch of cool examples bookmarked, but can't find them right now. Here's a brief article / interview with Matt with a bit more: https://blog.jetbrains.com/clion/2017/10/godbolting-your-cpp-code/ Cheers, - Brian On Thu, Oct 18, 2018 at 3:17 PM Prentice Bisbal via Beowulf < beowulf@beowulf.org> wrote: > I know I'm a bit late to this conversation. Been too busy to lurk here > lately. But I wanted to respond to this comment: > > > Lastly Jason mentioned IncludeOS http://www.includeos.org/ > > these gusy are implementing something I have tossed about on this list > > in the past - running applications in a lightweight OS without all the > > overhead of a multitasking system. > > I dont know that much about it - is anyone from that company on the list? > Lightweight operating systems for HPC is definitely a thing the IBM Blue > Gene systems used a lightweight kernel called CNK (Compute Node Kernel). > While not based on Linux, it used a subset of the Linux system call API > for its own system calls portability reasons. It was single-tasking, > since for an HPC job on a system like the Blue Gene (no node sharing > between jobs), there was no need to manage multiple tasks. > > https://en.wikipedia.org/wiki/CNK_operating_system > > I don't know much about Compute Node Linux (CNL), which is used on Cray > systems. I believe it is a stripped down version of Linux, but not sure > how stripped down it is. > > https://en.wikipedia.org/wiki/Compute_Node_Linux > > Here's some links to more information/other lightweight kernels, like > Puma and Catamount, in no particular order. > > > https://www.cresta-project.eu/images/WhitePapers/cresta_whitepaper_2_2014.pdf > > https://ieeexplore.ieee.org/document/323279 > > > https://www.researchgate.net/publication/228816883_Software_architecture_of_the_light_weight_kernel_Catamount > > https://en.wikipedia.org/wiki/Lightweight_Kernel_Operating_System > > Prentice > > On 09/09/2018 11:50 PM, John Hearns via Beowulf wrote: > > Chris Samuels recent post reminds me. > > I went to a fascinating and well delivered talk by Jason Hearne McGuiness > > > > https://www.meetup.com/ACCULondon/events/253570550/ > > https://accu.org/index.php/accu_branches/accu_london > > Slides are here: > > https://github.com/acculondon/2018-September > > > > I would encourage everyone to give this presentation at least a browse. > > Jason has done a lot of work in comparing the assembler code emitted > > by C++ compilers for simple statement blocks. Even within the g++ > > series there are wildly different assembler sequences emitted. And of > > course differences between Intel and Clang. > > I would have naively assumed that within g+++ at least as improvements > > are made then there would be some commonality - ie an evolution. But I > > would be wrong. > > > > Jason work in HFT so the default path loaded in IF statements (for > > instance) is important for low latency. > > Jason also did a lot of work in comparing performance before and after > > the Spectre/Meltdown fixes. There is a huge amount of work gone into > > that. > > > > One other takeaway - the choice of Linux OS is critical. Really. > > Common wisdom is that OS choice accounts for approx. 4% of performance > > difference. > > Not so. > > There isa big difference between CentOS 6 and 7 (7 being better) and > > Ubuntu does not shine at all well on his FIX benchmarks. Gentoo does > > well - Jason being a fan of Gentoo. > > As I remember on these benchmarks OS choice can affect results by 20% > !!!! > > > > Lastly Jason mentioned IncludeOS http://www.includeos.org/ > > these gusy are implementing something I have tossed about on this list > > in the past - running applications in a lightweight OS without all the > > overhead of a multitasking system. > > I dont know that much about it - is anyone from that company on the list? > > > > John Hearns > > _______________________________________________ > > Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin Computing > > To change your subscription (digest mode or unsubscribe) visit > http://www.beowulf.org/mailman/listinfo/beowulf > > _______________________________________________ > Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin Computing > To change your subscription (digest mode or unsubscribe) visit > http://www.beowulf.org/mailman/listinfo/beowulf >
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