Live data from Hacker News

Spacex Launch Webcast: Formosat-5 Mission

spacex.com

51–59 of 59 posts

Re: Spacex Launch Webcast: Formosat-5 Mission

#52
post #7

Earlier quoted context omitted.

Every time I've watched a landing, the video feed is janky. One might speculate that they don't want to live-stream an embarrassing failure but that seems a bit odd when it would be more embarrassing to have an explosion during launch, losing the payload. Edit: vvvv that sounds quite reasonable, you'd think they'd do something like throw a buoy 100m away to house the actual satellite link and just do wifi from the ba…

No need for speculation - the feed never cuts out on the return-to-launch-site landings. It's only wonky on the ship landings. Bouys bounce around a lot - the drone ships have special station-keeping thrusters to stay in place.

The rocket engines also put out a ton of ionized particles that can interfere with the satellite signal.

Re: Spacex Launch Webcast: Formosat-5 Mission

#53
post #7
post #4

Earlier quoted context omitted.

And as always, the live video feed of the landing was clunky :). They should nail one with a steady stream.

Every time I've watched a landing, the video feed is janky. One might speculate that they don't want to live-stream an embarrassing failure but that seems a bit odd when it would be more embarrassing to have an explosion during launch, losing the payload. Edit: vvvv that sounds quite reasonable, you'd think they'd do something like throw a buoy 100m away to house the actual satellite link and just do wifi from the ba…

You're underestimating the shock waves those engines produce. During launches you see camera footage from miles away shaking as the engines go to full power.

Of course there are solutions, but they're all expensive, and SpaceX has better things to spend money on. It's not like the footage doesn't exist - we're just not getting it live.

Re: Spacex Launch Webcast: Formosat-5 Mission

#55

Earlier quoted context omitted.

With a good CMake configuration and Ninja and ccache, a minute or two max. Your CMake makes incremental builds safe, and the ccache saves you when switching between branches.

CMake helps a good bit, ccache goes further, and ninja helps a bit too. But none of them can help templated header-only libraries with complex interdependencies. It gets particularly bad when the developer #includes a convenience header to bring in _everything_ in the library instead of just what they need.

Agreed. Good use of PImpl when you have large external header-only libraries is also generally recommended to keep the dependency graph nicer.

Also from what I've seen, large header-only codebases tend to be external and thus generally don't change that much, so if you can limit your own internal dependency tree ccache can still save you.

Re: Spacex Launch Webcast: Formosat-5 Mission

#56
post #48

Earlier quoted context omitted.

Not everyone is working on projects that are little more than CRUD webapps. I've worked on code that took hours to compile even on beefy machines.

I've worked on code that took that long to compile, and the cause of the problem was usually bad recursive makefiles doing work over and over again. At the other extreme I've also worked at Google and have seen insanely complex C++ code bases compile in 30 seconds flat. Multiple hour build times usually show that nobody smart enough had the interest and authority to solve the problem properly. It doesn't generally me…

OK, that's great for google, but "complex" doesn't necessarily mean much. Do you think the linux kernel devs are slouches? The gcc devs? Both of those projects take hours to compile on reasonable hardware, and that's not for lack of trying.

Also, sometimes it's not about code, it's about digital assets, which is going to be IO bound. I've worked on projects that took a full working day to do a clean compile and others where it was necessary to do binary integrations instead of code because the overall build time would otherwise be measured in days or weeks.

Re: Spacex Launch Webcast: Formosat-5 Mission

#57
post #50

Earlier quoted context omitted.

you should probably become more experienced in c/c++ development before sharing your opinion

You should see how quick C++ compilation times can be a competent organization like Google before dismissing that opinion.

Are you talking about clean builds or incremental builds?

Re: Spacex Launch Webcast: Formosat-5 Mission

#58
post #50

Earlier quoted context omitted.

You should see how quick C++ compilation times can be a competent organization like Google before dismissing that opinion.

Are you talking about clean builds or incremental builds?

They usually do incremental builds. And a lot of work goes into reproducible builds so that incremental builds can be trusted. But even clean builds are typically minutes of wall-clock time. Not hours.

Of course part of the trick is that work has been distributed across a cluster, so a lot longer was spent compiling than that...

Re: Spacex Launch Webcast: Formosat-5 Mission

#59

Earlier quoted context omitted.

How long should a giant C++ code base take to compile?

How giant is giant? I've seen tens of thousands of lines of code compile in 30 minutes. I've seen a hundred thousand lines of code compile in 2 minutes. It really depends on how the project is laid out. If you're using lots of header-only libraries and try to compile monolithically (like soooooo many C++ applications do these days), you're going to have a bad (compile) time.

tens of thousands? that's small. we're talking MLOCs here.
Post reply on HN