8 ms·

> At the risk of sounding stupid, I have no idea how bit-shifting and bitwise operators work, though I've worked in the field for over a decade and am now a Sta

> At the risk of sounding stupid, I have no idea how bit-shifting and bitwise operators work, though I've worked in the field for over a decade and am now a Staff Engineer or whatever. There, I said it. I mean no offense, but honestly I'm a bit flabbergasted that anyone who has worked in programming computers for over a decade wouldn't have acquired this exceptionally basic bit of computing knowledge.

sudhirj 5y ago
It simply hasn't come up. I've written accounting and billing software that processes millions without using bit shifting, logistics solvers that do multithreaded depth first search systems on lazy graphs without bit shifting, ticketing systems that sold millions of tickets correctly without bit shifting etc. I'm sure there are plenty of use cases out there, I just haven't worked on them.
- thechao 5y ago
  The right algorithm beats out low-level every time. Think of bitwise operators as a vector unit, but the scalar is a bit. That’s it.
- AnIdiotOnTheNet 5y ago
  It's not that they haven't come up in their job that's strange, but that they were never exposed to this level of base computing principle at any point in their career.
- hnick 5y ago
  Would you have recognised the opportunity to use it, not knowing how it works? Sometimes when we learn a new technique we suddenly see all the places it can be used that we didn't know about before. There's the old (probably apocryphal) story about the landscaper who was able to fire one of his staff when a customer told him he can calculate the side of a right-angled triangle without measuring all 3 sides. What he did worked for him, he just didn't know there was a better way. Anyway I do agree in this case you are probably correct. I think most programmers these days use bitwise logical operators for flags and rarely if ever bit shift outside of system code.
  - sudhirj 5y ago
    I almost had to learn it once for flags, but Go has iota and constants and Java has enums, and stuffing flags into an integer and storing that in Postgres or Redis would have made the problem arguably worse. Just used a Set.
vsareto 5y ago
How do you simultaneously know what bit shifting is but then not know that you can easily avoid it completely for a career?
- sudhirj 5y ago
  I know that it's the manipulation of binary numbers, and I do know what binary numbers are. But I've never operated on binary numbers professionally. I did do some AND OR NOR NOT XOR gate diagrams in high school and college, but haven't looked at binary numbers or thought in binary numbers since then.
  - AnIdiotOnTheNet 5y ago
    Ok, so it isn't as though you weren't exposed to the concept at least. The way you phrased what you said made it sound like boolean logic itself might be alien to you. Still, there's such a tiny conceptual distance from the gates to bitwise operators that I'm still a bit surprised you didn't acquire it by osmosis.
    - sudhirj 5y ago
      The Boolean logic part is applicable everywhere, so that's actually unrelated to binary arithmetic or bit-shifting. Stuff like Demorgan's theorem etc I practice more in the context of simplifying if-else statements than binary operations. So there hasn't been enough significant overlap to spread into.
lootsauce 5y ago
20 years of application development and I’ve used bit shifting a couple times, none of them were all that essential or much better than the alternatives. It’s a bit condesending and par for the course on HN to be flabbergasted at someone’s lack of knowledge of something but honestly there are career paths where it truely does not matter.
- AnIdiotOnTheNet 5y ago
  Because it is something that naturally flows from having an understanding of boolean logic and that computers store data in binary digits. Being a "software engineer" who doesn't understand this seems to me like being an architect who doesn't understand trigonometry or something.
  - WJW 5y ago
    I mean, if you work as a Staff engineer in a department that only does web app development (say, working at Shopify on their rails codebase) I can easily see that you wouldn't come into any contact with bitwise operators at all. Rather, your time is probably better spent on scaling databases, refactoring codebases and other such higher-level things.
  - pcthrowaway 5y ago
    Believe it or not, there are many different kinds of software engineering, many of which don't require you to know anything about binary or bitwise arithmetic. I don't know that I've ever used these as a full stack web developer, but I did learn it in my Computer Science program; the only time I think about the bit position of something is when setting/viewing file permissions, or reading source code for a library which does deal with this (there are legitimate reasons to use bitwise operators in JS for things like hashing, cryptography, secure string generation, etc.) But really, there are people doing software engineering who have never thought about this, and while I agree that any blind spot in knowledge is detrimental (and everyone has some blind spots), it's condescending to suggest that this specific blind spot is noteworthy to the point of lacking foundational knowledge. Your software engineering isn't the only type of software engineering.
sudhirj 5y ago
I also have no idea how to properly do memory management, every language I've worked with has had garbage collection. I know the languages I write in use malloc or something to get more memory, but that's it. Never called it, don't know how it works. For flabberg-ammo for that gasty feeling.
- AnIdiotOnTheNet 5y ago
  I can understand how this situation happens, but honestly it really bothers me that it is the case. I see all this bloated slow software everywhere that pauses all the time and it is hard not to see "I've never done memory management" as part of the cause.
  - sudhirj 5y ago
    That might not be due to memory management - a lot of my work is in Go and Java, selling very high demand inventory to millions of people (opening night movie tickets across tens of thousands of screens and shows across the entire country) and the APIs are not slow and do not (noticeably) GC pause. But both Go and Java / JVM allow people to do high-value work without worrying about memory management (other than leaks of course). No allocations, free / release, no pointer arithmetic. Even the concept of pointers in Go isn't actual memory addresses but value/reference semantics. The only time I came close to having to manage memory was iOS apps, but then ObjectiveC added ARC and Swift came along, so nope.
    - AnIdiotOnTheNet 5y ago
      It certainly feels like a GC pause, but it could be a lot of things. Regardless of the cause I feel like the fact that people don't think about how memory is managed is indicative of the real problem: people are programming computers without really understanding how they work. And while that is fine, even encouraged, for a lot of use cases I think anyone calling themselves a professional programmer should be held to a higher standard.
      - 5y ago
SavantIdiot 5y ago
I think programming has become so high-level that there's a lot of fundamental computer science that is largely ignored. I mean, I'm sure this person has no idea what an ISA, cache, CAM, or pipeline is either, but you don't need to know to write front-end JavaScript. It does unnerve me as well, since it is so fundamental in my mind. But hey, maybe there is just so much to learn there's no time to teach computer architecture anymore? If you want to feel humbled, read the book "Hackers Delight". It is about 300 pages of mostly bitwise algorithms and operations. I thought I knew a thing or two from decades coding, but this book goes so deep that my brain just shut off. https://www.powells.com/book/hackers-delight-1st-edition-9780201914658 https://www.powells.com/book/hackers-delight-1st-edition-978... EDIT: Upon further pondering, bitwise operations make certain assumptions about machine word size for that context. It could be dangerous for higher level languages to allow bitwise ops if the # of bits isn't known, as this context of instructions is generally tied to the hardware: the opposite of high level languages!
- mettamage 5y ago
  Nor do companies care that you know this when applying for a web developer position. IMO they should care since it shows you're capable of learning about different fields in the software engineering field.
  - sudhirj 5y ago
    We definitely care if you’re capable of learning other fields - we check for breadth in static and dynamic languages, SQL and NoSQL knowledge, UX and systems design, performance optimisation, a sense of aesthetics, writing and communication skills and more. We’d rather people spend time learning these than binary arithmetic or regex operators or SIMD instructions.
croes 5y ago
Just wait until Copilot is widely used. There will be a whole group of cargo cult programmers.
deleted 5y ago
[deleted]
fmakunbound 5y ago
10 years of one year's experience, probably.
- sudhirj 5y ago
  Heh, no, I'm happy to say I've worked in a wide range of industries, countries, programming languages, datastores, team compositions, roles, front & backend, side projects and own products. I'm just saying non of them required shifting bits.
smichel17 5y ago
https://xkcd.com/1053/ https://xkcd.com/1053/
look_lookatme 5y ago
A lot of software development is just "executing recipes" and there's nothing wrong with that: https://youtu.be/Nb2tebYAaOA?t=1363 https://youtu.be/Nb2tebYAaOA?t=1363
handrous 5y ago
Been writing code for pay since about 2000. I think I've bit-shifted in anger, like... twice. I 1000% could not do anything useful with them without consulting a reference, as with most anything else I don't do on an ~weekly basis. [EDIT] rather, that's all bitwise operators. I know I've used them once (in a "write it once, never touch it again" kind of context) and maybe one other time but recollection's hazy. Just a basic bit-packing thing IIRC, for the one I recall.
BrandoElFollito 5y ago
I started with C 30 years ago, wrote my PhD thesis in pain, tears and C, and then developed at a more or less amateur level until today (thankfully not in C anymore). I read about bit-shifting operations but never, ever had the need to use them. So I did not push further and just know that they exist and that they look like <<. I hope I did not made your flabbergastering worse. Ah, I also wrote a (tiny) bit of the Linux kernel in ~1994 (what today would be modules). And still survived without <<
atomashpolskiy 5y ago
Yeah, not everybody has to work with networks or cryptography, but I would've imagined that people at least read libraries that they use (to figure out what's going on under the hood) and inspect/debug low-level stuff from time to time.
wutwutwutwut 5y ago
I mean no offense, but honestly I'm not a bit flabbergasted at all that anyone has your view. I keep seeing people acting as if the bubble they are in is a good representation of the world as a whole, and every indication that maybe they are wrong is met with a big surprise. If you are truly flabbergasted by this you need to try to find a way out of your bubble so you can understand reality better.

sudhirj 5y ago

It simply hasn't come up. I've written accounting and billing software that processes millions without using bit shifting, logistics solvers that do multithreaded depth first search systems on lazy graphs without bit shifting, ticketing systems that sold millions of tickets correctly without bit shifting etc. I'm sure there are plenty of use cases out there, I just haven't worked on them.

thechao 5y ago
The right algorithm beats out low-level every time. Think of bitwise operators as a vector unit, but the scalar is a bit. That’s it.
AnIdiotOnTheNet 5y ago
It's not that they haven't come up in their job that's strange, but that they were never exposed to this level of base computing principle at any point in their career.
hnick 5y ago
Would you have recognised the opportunity to use it, not knowing how it works? Sometimes when we learn a new technique we suddenly see all the places it can be used that we didn't know about before. There's the old (probably apocryphal) story about the landscaper who was able to fire one of his staff when a customer told him he can calculate the side of a right-angled triangle without measuring all 3 sides. What he did worked for him, he just didn't know there was a better way. Anyway I do agree in this case you are probably correct. I think most programmers these days use bitwise logical operators for flags and rarely if ever bit shift outside of system code.
- sudhirj 5y ago
  I almost had to learn it once for flags, but Go has iota and constants and Java has enums, and stuffing flags into an integer and storing that in Postgres or Redis would have made the problem arguably worse. Just used a Set.

vsareto 5y ago

How do you simultaneously know what bit shifting is but then not know that you can easily avoid it completely for a career?

sudhirj 5y ago
I know that it's the manipulation of binary numbers, and I do know what binary numbers are. But I've never operated on binary numbers professionally. I did do some AND OR NOR NOT XOR gate diagrams in high school and college, but haven't looked at binary numbers or thought in binary numbers since then.
- AnIdiotOnTheNet 5y ago
  Ok, so it isn't as though you weren't exposed to the concept at least. The way you phrased what you said made it sound like boolean logic itself might be alien to you. Still, there's such a tiny conceptual distance from the gates to bitwise operators that I'm still a bit surprised you didn't acquire it by osmosis.
  - sudhirj 5y ago
    The Boolean logic part is applicable everywhere, so that's actually unrelated to binary arithmetic or bit-shifting. Stuff like Demorgan's theorem etc I practice more in the context of simplifying if-else statements than binary operations. So there hasn't been enough significant overlap to spread into.

lootsauce 5y ago

20 years of application development and I’ve used bit shifting a couple times, none of them were all that essential or much better than the alternatives. It’s a bit condesending and par for the course on HN to be flabbergasted at someone’s lack of knowledge of something but honestly there are career paths where it truely does not matter.

AnIdiotOnTheNet 5y ago
Because it is something that naturally flows from having an understanding of boolean logic and that computers store data in binary digits. Being a "software engineer" who doesn't understand this seems to me like being an architect who doesn't understand trigonometry or something.
- WJW 5y ago
  I mean, if you work as a Staff engineer in a department that only does web app development (say, working at Shopify on their rails codebase) I can easily see that you wouldn't come into any contact with bitwise operators at all. Rather, your time is probably better spent on scaling databases, refactoring codebases and other such higher-level things.
- pcthrowaway 5y ago
  Believe it or not, there are many different kinds of software engineering, many of which don't require you to know anything about binary or bitwise arithmetic. I don't know that I've ever used these as a full stack web developer, but I did learn it in my Computer Science program; the only time I think about the bit position of something is when setting/viewing file permissions, or reading source code for a library which does deal with this (there are legitimate reasons to use bitwise operators in JS for things like hashing, cryptography, secure string generation, etc.) But really, there are people doing software engineering who have never thought about this, and while I agree that any blind spot in knowledge is detrimental (and everyone has some blind spots), it's condescending to suggest that this specific blind spot is noteworthy to the point of lacking foundational knowledge. Your software engineering isn't the only type of software engineering.

sudhirj 5y ago

I also have no idea how to properly do memory management, every language I've worked with has had garbage collection. I know the languages I write in use malloc or something to get more memory, but that's it. Never called it, don't know how it works. For flabberg-ammo for that gasty feeling.

AnIdiotOnTheNet 5y ago
I can understand how this situation happens, but honestly it really bothers me that it is the case. I see all this bloated slow software everywhere that pauses all the time and it is hard not to see "I've never done memory management" as part of the cause.
- sudhirj 5y ago
  That might not be due to memory management - a lot of my work is in Go and Java, selling very high demand inventory to millions of people (opening night movie tickets across tens of thousands of screens and shows across the entire country) and the APIs are not slow and do not (noticeably) GC pause. But both Go and Java / JVM allow people to do high-value work without worrying about memory management (other than leaks of course). No allocations, free / release, no pointer arithmetic. Even the concept of pointers in Go isn't actual memory addresses but value/reference semantics. The only time I came close to having to manage memory was iOS apps, but then ObjectiveC added ARC and Swift came along, so nope.
  - AnIdiotOnTheNet 5y ago
    It certainly feels like a GC pause, but it could be a lot of things. Regardless of the cause I feel like the fact that people don't think about how memory is managed is indicative of the real problem: people are programming computers without really understanding how they work. And while that is fine, even encouraged, for a lot of use cases I think anyone calling themselves a professional programmer should be held to a higher standard.
    - 5y ago

SavantIdiot 5y ago

I think programming has become so high-level that there's a lot of fundamental computer science that is largely ignored. I mean, I'm sure this person has no idea what an ISA, cache, CAM, or pipeline is either, but you don't need to know to write front-end JavaScript. It does unnerve me as well, since it is so fundamental in my mind. But hey, maybe there is just so much to learn there's no time to teach computer architecture anymore? If you want to feel humbled, read the book "Hackers Delight". It is about 300 pages of mostly bitwise algorithms and operations. I thought I knew a thing or two from decades coding, but this book goes so deep that my brain just shut off. https://www.powells.com/book/hackers-delight-1st-edition-9780201914658 https://www.powells.com/book/hackers-delight-1st-edition-978... EDIT: Upon further pondering, bitwise operations make certain assumptions about machine word size for that context. It could be dangerous for higher level languages to allow bitwise ops if the # of bits isn't known, as this context of instructions is generally tied to the hardware: the opposite of high level languages!

mettamage 5y ago
Nor do companies care that you know this when applying for a web developer position. IMO they should care since it shows you're capable of learning about different fields in the software engineering field.
- sudhirj 5y ago
  We definitely care if you’re capable of learning other fields - we check for breadth in static and dynamic languages, SQL and NoSQL knowledge, UX and systems design, performance optimisation, a sense of aesthetics, writing and communication skills and more. We’d rather people spend time learning these than binary arithmetic or regex operators or SIMD instructions.

croes 5y ago

Just wait until Copilot is widely used. There will be a whole group of cargo cult programmers.

deleted 5y ago

[deleted]

fmakunbound 5y ago

10 years of one year's experience, probably.

sudhirj 5y ago
Heh, no, I'm happy to say I've worked in a wide range of industries, countries, programming languages, datastores, team compositions, roles, front & backend, side projects and own products. I'm just saying non of them required shifting bits.

smichel17 5y ago

https://xkcd.com/1053/ https://xkcd.com/1053/

look_lookatme 5y ago

A lot of software development is just "executing recipes" and there's nothing wrong with that: https://youtu.be/Nb2tebYAaOA?t=1363 https://youtu.be/Nb2tebYAaOA?t=1363

handrous 5y ago

Been writing code for pay since about 2000. I think I've bit-shifted in anger, like... twice. I 1000% could not do anything useful with them without consulting a reference, as with most anything else I don't do on an ~weekly basis. [EDIT] rather, that's all bitwise operators. I know I've used them once (in a "write it once, never touch it again" kind of context) and maybe one other time but recollection's hazy. Just a basic bit-packing thing IIRC, for the one I recall.

BrandoElFollito 5y ago

I started with C 30 years ago, wrote my PhD thesis in pain, tears and C, and then developed at a more or less amateur level until today (thankfully not in C anymore). I read about bit-shifting operations but never, ever had the need to use them. So I did not push further and just know that they exist and that they look like <<. I hope I did not made your flabbergastering worse. Ah, I also wrote a (tiny) bit of the Linux kernel in ~1994 (what today would be modules). And still survived without <<

atomashpolskiy 5y ago

Yeah, not everybody has to work with networks or cryptography, but I would've imagined that people at least read libraries that they use (to figure out what's going on under the hood) and inspect/debug low-level stuff from time to time.

wutwutwutwut 5y ago

I mean no offense, but honestly I'm not a bit flabbergasted at all that anyone has your view. I keep seeing people acting as if the bubble they are in is a good representation of the world as a whole, and every indication that maybe they are wrong is met with a big surprise. If you are truly flabbergasted by this you need to try to find a way out of your bubble so you can understand reality better.