Curiosity was built with 2.5 million lines of C

http://programmers.stackexchange.com/questions/159637/what-is-the-mars-curiosity-rovers-software-built-in/159638#159638?

by dustingetz • 14 years ago

102 33 14 years ago

programmers.stackexchange.com

rbanffy2• 14 years ago

I found it fascinating that the most productive C programmer on the team was a Python script.

Go Python! ;-)

edge177• 14 years ago

productivity != kloc's

autogenerated C is used sometimes for complex conditional nestings. in some failure situations it is programmatically more efficient or easier to trace issues if every condition is enumerated

rbanffy2• 14 years ago

I know that, of course. That's why I used a winking smiley.

In any case, programs that generate code is, at least for me, a code smell.

robomartin2• 14 years ago

I frequently use a couple of custom tools I created in Excel (for ease of data entry) to generate and maintain complex state machines and even-driven loop callback C code in embedded systems. That does not mean that the embedded systems were written in Excel. In this case Excel is simply leveraged as a productivity tool as I suspect might be the case for the use of Python scripts to generate chunks of code in the JPL case.

jebblue• 14 years ago

In the late 70's Viking had about 12 KBytes RAM (6000 WORDS) and 5 MBytes (40 MBit) tape storage.

http://en.wikipedia.org/wiki/Viking_program

EdiX2• 14 years ago

Most of it automatically generated, therefore it is not written in C.

edge177• 14 years ago

huh? it is auto-generated C as described in the post

jfoutz• 14 years ago

By that logic, it's written in machine code.

rat87• 14 years ago

A scheme or haskell(or c++) program that is compiled with a compiler that uses c as an intermediate form is still a scheme/haskell/c++ program. Even if the intermediate code is analyzed by a static analyzer or humans(especially if it's not modified, but possibly to some extent even if the intermediate code is slightly modified or used by other intermediate code written by hand) the source language is the actual language.

eliben3• 14 years ago

This really depends on the kind of code generation being used. There's "dumb" code generation, and there's a DSL.

In the "dumb" case, the input is usually some tabular data, and the code generator simply translates it to valid C syntax. It makes sense to say "it was written in C" in this case, although it's a bit moot since this is just data.

In the DSL case, the logic is actually coded in a different language, and the code generator translates it to C. Here it would be more difficult to argue that "it was written in C", because C just serves as a compiler intermediate language.

Naturally there are levels in between the above two, but the point is that it's difficult to judge without examining the actual module that was auto-generated.

edge177• 14 years ago

true, though it's unlikely that you would launch a DSL. far more likely that a lot of the code being generated is lookup tables and the like. engineers that write this sort of fault tolerant related code will do a lot of things the 'dumb' way because it's often less error prone or easier to trace failures. a number of friends work on space related things, and there tends to be an emphasis placed on not being overly clever (i.e. practices like return values being true or false rather than enumerations, etc)

sgrove• 14 years ago

I feel this is an interesting story to read alongside the OP: http://www.flownet.com/gat/jpl-lisp.html

eliben3• 14 years ago

There will always be someone lamenting that language X (insert Lisp, Smalltalk, Haskell or anything else here) is not being used instead of the horribly terribly utterly broken C, C++ or Java (yes, I'm being sarcastic). But in the end, pragmatic concerns win. Nobody works in vacuum, even if they really want to.

I'm a big fan of functional and otherwise dynamic language, but if I had to write my own Mars-landing controller, I would use C. No doubt there.

roma1n• 14 years ago

I wouldn't. I would go with spark ada. No doubt C has better tooling, though.

bitcracker• 14 years ago

> if I had to write my own Mars-landing controller, I would use C. No doubt there.

C is a good choice for code generation, as a replacement for Assembler. But I would never dare write mars landing code in C directly.

I guess the curiosity team used several languages destined for a 100% verified C compiler for a well defined subset of C.

mgurlitz• 14 years ago

Previous discussion: http://news.ycombinator.com/item?id=4344945

xmpir• 14 years ago

Why are people discussing this for so long? Does it make a difference whether it was 500k or 2500k lines of code? It was a huge project and that's it.

cbs• 14 years ago

Why are people discussing this for so long?

Because it's fascinating.

Its not the same old bullshit minutiae over-hyped as the latest and greatest thing, it's honestly a feat of human achievement. It means different things to different people. Creating inspiration, awe, and wonder. It shapes opinions on humanity, tech and life.

But forget all that for a second, and the intimate technical details of how things come together are still interesting to techy people. Even the logistics and implementation of traffic lights can tickle our curiosity. This thing is on another planet!

You sound like someone who has never built anything for just for fun.

StewartRen• 14 years ago

It was written in MSDOS Q-Basic

ANH• 14 years ago

Point of interest: In one of the press conferences yesterday they said they're planning to push an update to the rover's software soon after they get the X-band antenna deployed (which should have happened already).

robomartin2• 14 years ago

Well, the farther you abstract away from executable machine code the greater the inefficiencies introduced into the resulting machine code. Object oriented programming is there for the benefit of the programmer, the machine couldn't care less. The trouble is that any OO language will introduce unnecessary code into any given program. What I mean by "unnecessary" is that, if you were coding the solution in assembler you would, in all likelihood, not produce such code.

C let's you code at a level that is extremely close to the underlying machine language. If you are an experienced embedded developer you'll know exactly what code you are producing for the particular processor you happen to be working with.

I would not venture a guess, but I would not be surprised if the overwhelming majority of real-time, mission-critical systems out there are coded in C. The only other language I would consider would be Forth --which I have used extensively. I have played with the idea of going to something like C++. I have never found it to make sense in the context of a resource and horsepower-limited embedded system.

I don't know where the distain for C comes from. Yes, I am aware of the issues on can run into by writing unsafe code. Isn't part of our job to write safe code? I certainly do.

Curiosity was built with 2.5 million lines of C

Related Stories