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I found a 55 year old bug in the first Lunar Lander game

martincmartin.com

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Re: I found a 55 year old bug in the first Lunar Lander game

#91

Post by schiffern »

necovek wrote: post #84
martincmartin wrote: post #62

Earlier quoted context omitted.

Yeah, I think we're agreeing. :) So it turns out, before discovering the bug, I actually wrote code to find the optimal sequence when your choices are restricted to integers. I thought, along the same lines as you, "maybe if you burn 165 or 170 or something in the first non-zero term, then you could burn less on the 14 turn and still land." And this is how I know it's not possible, at least with integer burn rates. :…

I think they are saying that you need to switch to 199.999... lbs/s for all the 200 lbs/s burns, not just the last one. Just trying to clarify where you seem to be speaking past each other, though it seems that this might simply lead to a non-optimal strategy (i.e. taking more time to land than theoretically possible, however minute the difference is).

  >switch to 199.999... lbs/s for all the 200 lbs/s burns, not just the last one
That's not it. See here: https://news.ycombinator.com/item?id=40685081

Re: I found a 55 year old bug in the first Lunar Lander game

#93

Post by GMoromisato »

benjedwards wrote: post #13

If anyone is curious, in 2009, I discovered that Jim Storer was the author of the first Lunar Lander game and interviewed him about it (and also chronicled the history of the game beyond that). He later provided the source code, which was awesome. https://technologizer.com/2009/07/19/lunar-lander/index.html My favorite part is this: “After leaving high school I never thought about the game again,” says Storer. “Until…

I'm honored to be included in this article--I wrote Lander (1990) originally for Windows 2.x.

When I applied for a job to work on Lotus Notes (back in 1989), I showed the interviewer (Tim Halvorsen) my Lander game. He said, "That's pretty cool--let's try running it on Windows 3."

At first, I thought, cool! I get to see Windows 3 (which had not yet been released). But then he said, "Windows 3 runs everything in protected mode, so if you have any out-of-bounds pointer access, it will crash instantly. Let's see how you did."

I was on pins and needles the entire time.

But fortunately, Lander didn't crash, and Tim was happy. I ended up getting the job, which forever changed my career.

Re: I found a 55 year old bug in the first Lunar Lander game

#94

Post by AngryData »

necovek wrote: post #85
lionkor wrote: post #17

Earlier quoted context omitted.

Automobiles are more (wear-)efficient at braking when they use the engine to brake, not the brakes, so that would probably be a better approach to automate

Isn't that simply because the engine provides less resistance through the clutch than brakes do? Would clutch really be spent less than brake pads for the same braking power (light press on the brakes)? FWIW, modern flywheel clutch kits are way more expensive than brake pads, so the cost is not so clear cut anyway.

You aren't really using clutch surfaces to brake though, mostly you are relying on the friction and energy used to compress your intake air and blow it out the exhaust with either minimal or no combustion/fuel input, and if at speed air resistance. And everything else added up helps too like in friction in transmission and differentials and cam and crank bearings which are hopefully minimal, and also pumping coolant and oil and running the alternator, etc. In an automatic some will be lost lost in heating up fluid in the torque converter too.

Re: I found a 55 year old bug in the first Lunar Lander game

#96

Post by LegionMammal978 »

omoikane wrote: post #69
martincmartin wrote: post #9

Earlier quoted context omitted.

OP here. One interesting thing about FOCAL is that * has higher precedence than /. So in Lunar Lander, M*G/Z*K is what mathematicians and other languages would write M*G/(Z*K). I did a double take when I first saw that. :) As the Wikipedia article says, "This can cause subtle errors when converting FOCAL source code to other systems." Also, the IF syntax is a little limiting and hard to read, although I suppose progr…

Another curious feature is that the labels appears to be floating point, as in "G 5.9" appears to transfer control to line starting at "05.90".

They aren't actually floating-point: each label is a pair of numbers, the first denoting the group and the second denoting the line within that group. The groups have no semantic importance, they are only for organization.

Re: I found a 55 year old bug in the first Lunar Lander game

#97

Post by WalterBright »

mhh__ wrote: post #72
WalterBright wrote: post #53

Earlier quoted context omitted.

> and an impressive amount of capability for a high school senior It's only impressive because very few (none?) high schools teach calculus at the level required for his implementation. High schoolers are quite capable of handling that kind of calculus, it's just that the high schools don't teach it.

The UK stopped including calculus as part of physics even! I got told off for doing an integral.

How sad.

Re: I found a 55 year old bug in the first Lunar Lander game

#98

Post by elwell »

benjedwards wrote: post #13

If anyone is curious, in 2009, I discovered that Jim Storer was the author of the first Lunar Lander game and interviewed him about it (and also chronicled the history of the game beyond that). He later provided the source code, which was awesome. https://technologizer.com/2009/07/19/lunar-lander/index.html My favorite part is this: “After leaving high school I never thought about the game again,” says Storer. “Until…

Lunar Lander was one of the early games I tried to make a copy of as I was learning programming in high school: (Java applet!) https://github.com/celwell/space-landing

Re: I found a 55 year old bug in the first Lunar Lander game

#99

Post by ab5tract »

nox101 wrote: post #80
benjedwards wrote: post #13

If anyone is curious, in 2009, I discovered that Jim Storer was the author of the first Lunar Lander game and interviewed him about it (and also chronicled the history of the game beyond that). He later provided the source code, which was awesome. https://technologizer.com/2009/07/19/lunar-lander/index.html My favorite part is this: “After leaving high school I never thought about the game again,” says Storer. “Until…

That's awesome I just wanted to add, there's also mechanical lander games that pre-date lunar lander I can't find a picture. IIRC the machine was something like this https://content.invisioncic.com/r322239/monthly_10_2015/post... Except it had terrain and pits. A pit would light up and you needed to land in the pit (your ship landing would depress the button in the center of the pit). If you didn't aim well your ship…

Seems unlikely that a computer was involved in this.
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