Josef “Jeff” Sipek

Lua Compatibility

Phew! Yesterday afternoon, I decided to upgrade my laptop’s OpenIndiana from 151a9 to “Hipster”. I did it in a bit convoluted way, and hopefully I’ll write about that some other day. In the end, I ended up with a fresh install of the OS with X11 and Gnome. If you’ve ever seen my monitors, you know that I do not use Gnome — I use Notion. So, of course I had it install it. Sadly, OpenIndiana doesn’t ship it so it was up to me to compile it. After the usual fight to get a piece of software to compile on Illumos (a number of the Solaris-isms are still visible), I got it installed. A quick gdm login later, Notion threw me into a minimal environment because something was exploding.

After far too many hours of fighting it, searching online, and trying random things, I concluded that it was not Notion’s fault. Rather, it was something on the system. Eventually, I figured it out. Lua 5.2 (which is standard on Hipster) is not compatible with Lua 5.1 (which is standard on 151a9)! Specifically, a number of functions have been removed and the behavior of other functions changed. Not being a Lua expert (I just deal with it whevever I need to change my window manager’s configuration), it took longer than it should but eventually I managed to get Notion working like it should be.

So, what sort of incompatibilies did I have to work around?

loadstring

loadstring got renamed to load. This is an easy to fix thing, but still a headache especially if you want to support multiple versions of Lua.

table.maxn

table.maxn got removed. This function returned the largest positive integer key in an associative array (aka. a table) or 0 if there aren’t any. (Lua indexes arrays starting at 1.) The developers decided that it’s so simple that those that want it can write it themselves. Here’s my version:

local function table_maxn(t)
    local mn = 0
    for k, v in pairs(t) do
        if mn < k then
            mn = k
        end
    end
    return mn
end

table.insert

table.insert now checks bounds. There doesn’t appear to be any specific way to get old behavior. In my case, I was lucky. The index/positition for the insertion was one higher than table_maxn returned. So, I could replace:

table.insert(ret, pos, newscreen)

with:

ret[pos] = newscreen

Final Thougths

I can understand wanting to deprecate old crufty interfaces, but I’m not sure that the Lua developers did it right. I really think they should have marked those interfaces as obsolete, make any use spit out a warning, and then in a couple of years remove it. I think that not doing this, will hurt Lua 5.2’s adoption.

Yes, I believe there is some sort of a compile time option for Lua to get legacy interfaces, but not everyone wants to recompile Lua because the system installed version wasn’t compiled quite the way that would make things Just Work™.

Moving and Downtime

I’ll be moving my server over the next couple of days. I’m working on an email setup to make sure there’s no interruption there. The website and the blahg will however be down until Wednesday evening. Sorry for any inconvenience this may cause.

Task Spooler

For a couple of years now, I wished that I could have a mini-batch system on my computers that’d let me submit jobs and they’d execute when the resources became available. This would let me queue up large amount of work and it’d eventually all get processed. I even tried to hack up a dumb little Python script that’d loop over a file executing no more than one per core.

Then, yesterday, I stumbled across Task Spooler. It’s exactly what I was looking for! It lets me queue jobs, supports dependencies between jobs, etc.

I’m hoping to experiment with it in the next couple of days. I’ll let you know how it turns out.

DNS Fun

So, I decided to spring the ~30USD, and bought offtopic2.net. I moved Planet offtopic2 onto it. It was quite a bit of fun to set up a DNS server, have other DNS servers be slaves and transfer the zone data over. I should do stuff like this more often ;)

To Boldly Go...

Some time ago, I started helping with the maintainance of Galaxy — a Beowulf cluster right here at Stony Brook University. Up until two days ago, it consisted of:

Count CPU
6x Pentium III 1266MHz
46x Athlon MP 1800+ (1533MHz)
24x Xeon 2400MHz
18x Xeon 3000MHz
82x Xeon 3200MHz

That’s right, 176 nodes. Anyway, two days ago we took all the Athlons offline, because we got a shipment of nice 3400 MHz Xeons — about 50 of them. :)

I should get a copy of SPEC and see how it goes. ;)

(I’ll post some photos in near future.)

[unknown]

As promised, here’s a photo of us (two of the Galaxy people) bringing some nodes online:

Taking a break

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