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Testing is better than data structures and algorithms

nedbatchelder.com

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Re: Testing is better than data structures and algorithms

#91

Post by nick__m »

teraflop wrote: post #78
wubrr wrote: post #72

Earlier quoted context omitted.

No, it's called testing many concurrent operations. Implementing a complex concurrent algorithm based on your understanding of it, without proper testing is called luck, and often called delusion.

You can't easily, automatically test concurrent code for correctness without testing all possible interleavings of instructions, and that state space is usually galactically huge. It is very easy to write multithreaded code that is incorrect (buggy), but where the window of time for the incorrectness to manifest is only a few CPU instructions at a time, sprinkled occasionally throughout the flow of execution. Such a…

There is a cost benefit ratio and context that matters.

The repeat the concurent operations 1000times technique is adequate for a CRUD API but it's whofully inadequate for a database engine or garbage collector.

Re: Testing is better than data structures and algorithms

#92

Post by blind_tomato »

nice_byte wrote: post #7

ignore this advice. spend plenty of time studying data structures and algorithms as well as computer architecture. these are actually difficult things that take a long time to understand and will have a positive impact on your career. study the underlying disciplines of your preferred domain. in general, focus on more fundamental things and limit the amount of time you spend on stupid shit like frameworks, build syst…

I'll ignore your advice. It's one-sided and misleading, lacking the nuances the OP had.

Re: Testing is better than data structures and algorithms

#93

Post by sarchertech »

wubrr wrote: post #86
sarchertech wrote: post #74

Earlier quoted context omitted.

> Every place I worked at, that had any kind of reliable, high-throughput concurrent system Pretty much anyone with high throughput is running a high throughput concurrent system, and very few companies have an extensive suite of concurrency tests unless you just mean load tests (that aren’t setup to catch race conditions). The “reliable” part of that statement might be doing a lot of heavy lifting depending on what…

I gave you several concrete examples. Your claims of 'very few companies have...' aren't very convincing, and the apparent popularity of concurrency testing isn't really a strong argument for or against it's effectiveness or do-ability.

Did you Google “concurrency testing” and send me the top 5 results?

Re: Testing is better than data structures and algorithms

#95

Post by roxolotl »

IvyMike wrote: post #66

Always gonna have to side with Peter Norvig on this one: https://pindancing.blogspot.com/2009/09/sudoku-in-coders-at-... > They said, “Look at the contrast—here’s Norvig’s Sudoku thing and then there’s this other guy, whose name I’ve forgotten, one of these test-driven design gurus. He starts off and he says, “Well, I’m going to do Sudoku and I’m going to have this class and first thing I’m going to do is write a bun…

This totally misses the point of the article. The article agrees that knowing when a problem is a data structure and algo problem is a key strength. The article also isn’t saying that all development should be done TDD.

The point of the article is that knowing how to test well is more useful than memorizing solutions to algo problems. You can always look those up.

Re: Testing is better than data structures and algorithms

#96

Post by hxtk »

JackSlateur wrote: post #59
wubrr wrote: post #57

Earlier quoted context omitted.

I mean, in your example you just have an incomplete test suite. (Though writing a complete one is often unrealistic) While understanding algorithms and data structures is important, the only way you really know how well it works, and how well it's implemented is by thoroughly testing it. There are an infinite amount of clever algorithms out there with terrible implementations. You need both.

Testing concurrency is extremely hard For instance, get sql queries; You ran them, and you have no issue; Is your code sane ? Or is it because one query ran 10ms earlier and, thus, you avoided the issue ? I truly wonder if there is real world tests around this; I bet there is only algorithm and fuzzing;

I’ve long wished for an SQL error model: given a schema, query, and transaction isolation mode, what errors are theoretically possible?

I have a hard time answering this for Postgres, which disappoints me because I don’t see any reason it sounds very easy to answer, like there could be an extension to EXPLAIN that would dry run the query and list all the error states reachable.

Re: Testing is better than data structures and algorithms

#97

Post by fn-mote »

sarchertech wrote: post #93
wubrr wrote: post #86

Earlier quoted context omitted.

I gave you several concrete examples. Your claims of 'very few companies have...' aren't very convincing, and the apparent popularity of concurrency testing isn't really a strong argument for or against it's effectiveness or do-ability.

Did you Google “concurrency testing” and send me the top 5 results?

Kind of looks like it … the supporting evidence includes work from Microsoft: learning how to write concurrent programs. Surely not evidence that Microsoft is testing for concurrency bugs (of course they are).

Re: Testing is better than data structures and algorithms

#98

Post by wubrr »

sarchertech wrote: post #79
JackSlateur wrote: post #75

Earlier quoted context omitted.

What algorithm ? The whole idea is that algorithms are useless, and you should just write a bunch of tests and go with it Yes, if I write stuff with locks, I shall ensure that my code acquires and releases locks correctly This is completely off-topic with the original post; Also, you cannot prove something by tests; Just because you found 100000 cases where your code works does not mean there is not a case where is d…

> Also, you cannot prove something by tests; Just because you found 100000 cases where your code works does not mean there is not a case where is does not (just as you cannot prove that unicorn does not exist) :) That’s exactly it. For any non trivial program, there exists an infinite number of ways your program can be wrong and still pass all your tests. Unless you can literally test every possible input and every b…

For any 'non trivial' program there exists an infinite number of ways your program can be wrong but you still believe it's right.

Testing is not a perfect solution to catch all bugs. It's a relatively easy, efficient and reliable way to catch many common bugs though.

Re: Testing is better than data structures and algorithms

#99

Post by wubrr »

sarchertech wrote: post #93
wubrr wrote: post #86

Earlier quoted context omitted.

I gave you several concrete examples. Your claims of 'very few companies have...' aren't very convincing, and the apparent popularity of concurrency testing isn't really a strong argument for or against it's effectiveness or do-ability.

Did you Google “concurrency testing” and send me the top 5 results?

Maybe you should have googled 'concurrency testing' before telling me a story about how you worked at every tech company for 76000 years and never saw any concurrency testing lmao.

Re: Testing is better than data structures and algorithms

#100

Post by rr808 »

Do the people who love testing run JS or Python or something that compiles really quick? I've worked on some big projects and just to make a change, compile and run a unit test often takes 5-15 minutes. TDD works great if you have a trivial library in an interpreted language.
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