[HN Gopher] A Real Life Off-by-One Error
___________________________________________________________________
A Real Life Off-by-One Error
Author : leejo
Score : 310 points
Date : 2024-09-01 21:47 UTC (4 days ago)
(HTM) web link (leejo.github.io)
(TXT) w3m dump (leejo.github.io)
| anyfoo wrote:
| Great find!
|
| One comment on what the article says:
|
| > If this were actual code review the correct comment would be
| something like "this [piece] hasn't been used for years, it
| should be deleted". But this is something in physical space, and
| there would be arguments that removing it (them) means the route
| has changed, thus times are no longer comparable.
|
| Hmm, I think the correct analogy is rather a benchmark. Like code
| in a benchmarking tool or test, the whole climbing course does
| not serve any purpose, any actual goal, except to be completed as
| fast as possible.
|
| You wouldn't say "these instructions should be deleted because
| branch prediction and speculative execution in recent years have
| made it so that total cycle count is the same without them", for
| the reason stated ultimately after in the article already: That
| may not have been true in the past, and may change again in the
| future.
| bigiain wrote:
| > "these instructions should be deleted because branch
| prediction and speculative execution in recent years have made
| it so that total cycle count is the same without them"
|
| Then a new CPU architecture becomes popular, and spiders start
| winning every speed climbing event
| masklinn wrote:
| > You wouldn't say "these instructions should be deleted
| because branch prediction and speculative execution in recent
| years have made it so that total cycle count is the same
| without them"
|
| This is a very different statement than the original, and
| furthermore the original might actually trigger performance
| issues e.g. while the operation might not be used anymore it
| can have side effects (like triggering a prefetch) which end up
| affecting downstream code.
| yccs27 wrote:
| Yep, and even if the hold is not used anymore it can have
| side effects (like being in the way) which can end up
| affecting the climbing movements ;)
| yccs27 wrote:
| In the benchmark analogy, that piece would be a line of code
| that can be optimized away by the compiler. It could still
| matter if the code (course) is recompiled (rerouted) for a
| different architecture (climber).
| canucker2016 wrote:
| My analogy is that "The bug is in the error-handling portion of
| the common fast-path speed traversal of the climb."
|
| The fast path that the speed climbers commonly use doesn't
| involve the slower path involving the buggy portion.
|
| But if the climber can't get up/further using the fast path
| then the climber may be forced to take the slower path.
|
| Since the slower path is standardized, the climber knows how
| much effort/time is needed on the slower path.
|
| Except on the righthand side, the climber's typical effort
| along the slower "buggy" path is different from the typical
| slower path and will result in an even slower time aka the
| execution time in the error-handling path is larger than
| usual...
| AEVL wrote:
| Not an off-by-one error--at least not in spirit. Interesting
| nonetheless.
|
| I expected the article to eventually answer this puzzle:
|
| > The competition started and got through a number of rounds.
| There were some comments about how the climber on the left always
| won.
|
| Near the end:
|
| > The kicker is that the out of place hold hasn't been used in a
| long time. The climbers have optimised their route such that it
| is skipped. The same happens to the fourth hold from the bottom.
| So either being in the wrong place is immaterial to the climbers'
| technique as long as they don't get in the way.
|
| So it seems like the error discovered by the article author
| should not have conferred any advantage to the climber on the
| left.
|
| Anyone who can shine light on this matter?
| throwawayk7h wrote:
| It may not be a fencepost error, but I think it's still off by
| one.
| Arcuru wrote:
| The climbers had complained about an issue with the belay ropes
| on the right side that they also fixed.
|
| > A few of the climbers had said that the automatic belay ropes
| on the right hand lane did not feel right, so the cherry picker
| was replacing those and not the hold that I had noticed being
| out of place. The climbers had noticed something wasn't quite
| right, but hadn't said anything about the out of place hold.
|
| It was probably just two separate problems.
| merizian wrote:
| Even if the out of place hold were used, would you then
| conclude it to be causal? I still wouldn't rule out
| coincidence. Many discoveries happen as a result of
| investigating spurious patterns.
|
| Also the author rules out psychology, but I wouldn't,
| especially since there were multiple confirmed errors in the
| route preparation, which I expect could reduce one's trust in
| the fairness of the competition. In the moment, I might start
| to wonder, "If one hold was out of place, why not more? Is
| anyone even checking this?" even if untrue / unlikely.
| petsfed wrote:
| I've never been a competitive _speed_ climber, but I do
| understand that part of the process of precision is having
| cues for e.g. body position. So the fact that it's never
| actually touched is not necessarily the red herring it seems
| to be. Racecar drivers cue off of trackside landmarks to get
| their brake timing right, for instance.
|
| Certainly, the rope feel is a much more significant factor,
| since the feel of the rope tugging on your harness is a _non_
| visual part of your body position feedback (maybe "I know
| that I'm going fast enough /pulling hard enough if I'm
| outracing the rope retraction rate").
| fsckboy wrote:
| > _Not an off-by-one error--at least not in spirit. Interesting
| nonetheless._
|
| Literally it was an off-by-one error. Literally, literal
| meaning.
| hyperhello wrote:
| I think the poster meant off-by-one doesn't simply mean a
| plus or minus one error, like mispricing a $5.99 as $6.99,
| but instead must be born out of confusion as to whether an
| origin point is marked as a 1 or as a 0.
| Kiro wrote:
| > must be born
|
| There are other reasons as well. I think the more common
| causes are inclusive vs exclusive comparison errors and
| fencepost.
| whycome wrote:
| > must be born
|
| The spelling is off by one. It's "borne"
| fsckboy wrote:
| > _The spelling is off by one. It 's [not "born" it's]
| "borne"_
|
| the spelling was actually off by e , so you're stilll off
| by 1.71828...
| fmbb wrote:
| Off-by-one is not born from the base of the index. It is a
| general problem a lot of people run into in a lot of
| different contexts.
|
| It's for example called "the fencepost problem":
| https://betterexplained.com/articles/learning-how-to-
| count-a...
|
| I agree subtracting or adding one to any number is not the
| problem. It has to do with counting.
| fsckboy wrote:
| > _I agree subtracting or adding one to any number is not
| the problem. It has to do with counting._
|
| if you are sprint climbing and you put your hand out to
| grab and you add or subtract the number 1 from where your
| hand needs to be, it is a problem or contributes to a
| speed difference.
| richrichardsson wrote:
| Perhaps the pieces are placed by counting a number of holes
| from piece A to piece B? That's a perfect recipe for an
| off-by-one: at which point relative to piece A do you start
| counting.
| Robbsen wrote:
| > So it seems like the error discovered by the article author
| should not have conferred any advantage to the climber on the
| left.
|
| They might not use the hold by physically touching it, but they
| might still use it as a visual indicator of where the other
| holds are in relation. These competitors are used to the same
| layout for many years. If there is a slight misrepresentation
| it can surely put them off.
| jhncls wrote:
| People are misunderstanding the meaning of an off-by-one error.
| Suppose the plan states that hold A and hold B need to be 11
| holes apart. In the true spirit of the off-by-one error, this
| can be interpreted in 3 ways:
|
| - either as 11 empty holes between the holds; - as 11 holes,
| start counting 1 just above hold A; - or as 11 holes, start
| counting with hold A as number 1.
|
| Another real-life example, is a plumber who tells the
| construction worker that the distance between the holes for hot
| and cold water needs to be 15 cm. This was meant to be measured
| center to center, but the constructor worker interpreted it as
| the distance from the right side of the first hole to the left
| side of the second. The result can still be admired in our
| house, 10 years later.
| ano-ther wrote:
| They run the whole 15 meter up in about 5-10 seconds (quite
| amazing to watch: https://m.youtube.com/watch?v=8O4g8JmWn9E ).
| At that speed, a small disturbance from the path they
| internalized means that they need to switch back to thinking
| which will take them out of their flow.
| rockfishroll wrote:
| It's true that modern competitive speed climbers don't use that
| hold. The collective optimization of the route is hilariously
| serious (it's an olympic sport after all) and the different
| optimizations have names, like 'The Tomoa Skip'.
|
| But I think it's possible that 'extra' holds are potentially
| like 'junk' DNA. People fall into the trap of thinking that DNA
| is useless if it's never transcribed, but we know that's not
| actually the case. Non-expressed DNA can do things like alter
| binding affinity for neighboring sequences, affecting how often
| those neighboring sequences are expressed. I think it's
| possible that climbers are taking in a lot of information
| subconsciously as they sprint through this route in order to
| mike very small adjustments. The position of surrounding holds,
| even ones they never touch, could very well be a part of that
| information stream. They're fighting over hundredths of a
| second, so even a very small effect could be meaningful.
| db48x wrote:
| They're all in real life.
| cortesoft wrote:
| People use "real life" and "not in a computer" interchangeably
| db48x wrote:
| Those people are wrong.
| sanderjd wrote:
| There is no right or wrong, there is only "what people mean
| when they say words".
| db48x wrote:
| No, it's definitely possible to use words incorrectly.
| necovek wrote:
| That's not in conflict with what the parent said.
|
| People can mean something else than you when using the
| same words, and they might not be wrong as those word
| definitions might be acceptable too (and they might
| change over time too).
| cortesoft wrote:
| And who is the arbiter of which use is correct? Language
| is always evolving and changing, the definitions of words
| you grew up with were just the definitions at that time.
| The meaning of a word is only defined by how people use
| and understand it.
|
| It is possible to use words incorrectly, but if 90% of
| people use a word in a certain way, that becomes the
| definition.
| Bjartr wrote:
| Colloquialisms like "in real life" are correct usage.
| Just because it's not literal doesn't mean it's wrong
| because the information contained in verbal and written
| communication is affected by its context, including the
| society and culture it arose within.
| sanderjd wrote:
| I think the simpler way to think about this is that it's
| definitely possible (and common) to use words
| _confusingly_.
|
| That is, you can use words in such a way that many people
| misunderstand what you mean. You could then call that
| usage "incorrect" if you want, and I wouldn't quibble too
| much with that, but the more important reason not to use
| those words in that way is that people don't understand
| you.
|
| But in this case, this usage of "in real life" is not
| confusing anyone. Even those who pedantically quibble
| with it being "wrong" actually understood what was meant.
| sobriquet9 wrote:
| Unless we live in a simulation.
| imp0cat wrote:
| Remember all those time you've bitten your own tongue while
| chewing? Those are all off-by-one errors in the simulation.
| :)
| enneff wrote:
| Some can be imaginary no? Or do you think everything is real
| life? In which case what's the meaning of "real life"?
| GrantMoyer wrote:
| Real life v.s. IEEE-754 life
| renewiltord wrote:
| That's a fantastic find. I imagine some standard CV tool can spot
| this since the holds are grid-aligned. We should probably have
| something like that. It's crazy how good human pattern-
| recognition can get when trained on things. What a spot by you.
|
| Also, by the way, where is the photo on your about page:
| https://images.squarespace-cdn.com/content/v1/60f40aa1942bba...
|
| I feel like it's Crater Lake, Oregon, but considering where you
| live it's probably somewhere in Switzerland. Looks lovely.
| leejo wrote:
| It is Crater Lake, from a second visit this summer.
| stijnstijn wrote:
| You could also simply take two photos and overlay them. The
| difference would be obvious immediately to the human eye.
| delgaudm wrote:
| If you cross your eyes and look at the routes as if it were a
| single stereoscopic image overlaying one route on top of each
| other, the misplaced hold jumps out at you immediately.
| pooriar wrote:
| I just did it and it didn't jump out for me at all. Odd
| pavon wrote:
| I usually find it easier to relax my eyes (focus too far
| rather than too close), and so the opposite occurred - most
| of the holds appeared to float in a single plane (slightly
| wavy perhaps due to lighting differences), while the
| incorrect hold was sunk further back.
| LeonB wrote:
| Same! I couldn't get it to work because that sailboat was in
| the way.
| Miraltar wrote:
| It's so weird ! The badly placed hold just disappears once
| all the rests aligns. My brain seems to dismiss it as an
| error on its part
| iwontberude wrote:
| Same, after some practice I could close one eye at a time
| and see the movement but it was hard to maintain the eye
| crossing with one eye closed
| zeekaran wrote:
| Took me a bit to realize the last photo has it correctly, and
| to stop trying to find the discrepancy there. Looking at only
| the first image it pops out to me because the wrong one is
| floating closer to my eyes than the rest.
| lilyball wrote:
| Good idea. I just tried that on the first image of the whole
| route (after zooming in a bit) and the misplaced hold looks
| like it's floating in space away from the wall.
| whycome wrote:
| Yeah with each being slightly offset from the other, it
| introduces a fake parallax while the others should align
| perfectly and remain flat.
| dkbrk wrote:
| I tried this, and while I didn't have any difficulty
| establishing a stereoscopic view it didn't jump out for me at
| all. I perceived the blue line floating on top of the problem
| handhold, but the handhold seemed to be on the same plane as
| all the others. Knowing it was the problem one, I could use the
| stereoscopic view to see it, but without already knowing I
| don't think it would be apparent.
|
| This is odd to me since I've successfully used stereoscopy in
| the past to find small differences. For some reason, with this
| image, rather than causing a change in perceived z-level, my
| eyes fight for dominance and my left ends up winning.
| carlmr wrote:
| >This is odd to me since I've successfully used stereoscopy
| in the past to find small differences.
|
| Same, I think there are too many other things around it to
| make it work for me though.
| mhandley wrote:
| It took me a little while, because that blue line is
| definitely a distraction. But once the other holds all
| settled down to being properly in the plane and sharply
| focused, and I ignored the blue line, the misplaced one was
| clearly above the plane.
| sukmaagung wrote:
| It works. It is actually my secret technique when solving "find
| five differences".
| uvesten wrote:
| Now I'm one of the happy 10000!
| jve wrote:
| For people who may not understand your comment:
| https://xkcd.com/1053/
|
| I'm also one of them... actually not, I'm not "in US" :)
| qwertox wrote:
| Sometimes I also use this as a code diff tool. But it's most
| fun for those image puzzles.
| Dwedit wrote:
| Speaking of trivializing a challenge:
|
| There's a challenge where you see words like "RED BLUE YELLOW
| GREEN PURPLE", but they are written in color different to
| their name. You are challenged to say the color of the text
| and not read the word out loud.
|
| Intentionally defocusing your eyes makes that challenge
| trivial.
| sebtron wrote:
| I don't understand how this works. If I cross my eyes, the
| images become extremely blurry. I can't even tell if they are
| precisely overlapping or not, let alone see if one of the holds
| is out of place.
|
| Am I the only one?
| danbruc wrote:
| That needs training, took me quite some time to learn this in
| the early 90s when the Magic Eye books [1] came out and
| autostereograms could be found in many newspapers. I
| personally also never learned to cross my eyes, I instead
| make them look parallel, see the diagram in [2]. Once you
| have learned it, it is hard to unlearn, to the point that
| once in a while my eyes and brain will snap onto repetitive
| patterns like grid paper or just text without any intention
| to do so.
|
| [1] https://en.wikipedia.org/wiki/Magic_Eye
|
| [2] https://en.wikipedia.org/wiki/Autostereogram
| robotguy wrote:
| >once in a while my eyes and brain will snap onto
| repetitive patterns like grid paper or just text without
| any intention to do so.
|
| When autostereograms were all the rage in the late 80's I
| had a program on my Mac Plus that let me make/edit them and
| I used to edit for hours WHILE looking at them in 3D. Then
| one time I was walking down a hallway with a repetitive
| wallpaper pattern, my eyes did the thing, the entire
| hallway appeared to shift in front of me, and I stumbled
| and fell.
| s3krit wrote:
| > Once you have learned it, it is hard to unlearn, to the
| point that once in a while my eyes and brain will snap onto
| repetitive patterns like grid paper or just text without
| any intention to do so.
|
| Rare that I meet someone else that does this. I learned how
| to do magic eye puzzles as a young child, I think my first
| was in a magazine and I 'solved' it the standard way of
| placing it close to your nose then slowly pulling back.
| Before long I could just do it on command and as an adult I
| find myself doing it all the time, often unconsciously.
| Makes spot the difference puzzles trivial, that's for sure
| gre wrote:
| How about birthdays? When you turn "1" it's your second birthday.
| Or counting three seconds. Start counting zero..one..two..three.
| taraparo wrote:
| The number on your yearly "birthday" is not the number of
| birthdays you had (you only have one birthday) but the number
| of years you survived since your birth.
|
| So the day of your fifth birthday is the first day of your
| sixth year alive.
| noahlt wrote:
| array.length
| gre wrote:
| Birthday vs birth day but yeah. It works if you say it
| dasyatidprime wrote:
| I've generally seen "birthday" (within a year; recurs)
| versus "birthdate" (happens once).
| ars wrote:
| Jewish law sometimes counts from 1 instead of 0 for birthdays,
| so a newborn is not 0 years old, they are in their 1st year.
| (But it's written as "when they are 1", so you have to know
| which counting method is being used.)
| hangonhn wrote:
| Chinese traditional age counting does the same. My mother had
| to constantly explain to our relatives when I tell them my
| age -- I use Western conventions.
| Fred27 wrote:
| Korea has a system similar to this. You start at age 1 and get
| one year older each New Year's Day.
| https://www.90daykorean.com/korean-age-all-about-age-in-kore...
| whycome wrote:
| They changed the system last year after using it for many
| years (+/-1).
|
| https://www.aljazeera.com/amp/news/2023/6/28/why-are-
| south-k...
| BobAliceInATree wrote:
| You wouldn't want to remove unused holds, because in the future,
| someone may find a more efficient path the makes use of that
| hold, but ignores other ones.
| mauvehaus wrote:
| Sometimes climber, but not a speed climber: it would be
| vanishingly unlikely for a hold that far left of the button to
| end up on a more efficient route. Closer to the middle of the
| route, maybe, but it'd be a sharp jog to the right to hit the
| button from having any appendage on that hold.
| stijnstijn wrote:
| This is indeed what is argued in the article.
| quantadev wrote:
| An AI image prompt could easily detect the misplace grip, but
| there's probably no other sport that needs to detect exact
| placements of things is there?
| superb_dev wrote:
| A few seconds in an image editor could do it too
| quantadev wrote:
| Right. AI however could take into account skew angles and
| perspective tho, so you could probably photograph something
| from any angle at all and as long as all the pixels are there
| the AI can tell you of something's out of place.
| crote wrote:
| Which can also be trivially done in any halfway-decent
| image editor. Algorithm-wise, it'd probably look a lot like
| QR code detection - which of course doesn't need any kind
| of fancy AI.
| quantadev wrote:
| What I mean is you can probably get this to work with
| pure prompt engineering, and English language just by
| saying stuff like "Here's an image with correct hold
| positions", and then submit another image that says "Are
| the positions in this image correct." I just meant basic
| image understanding of AI, like what OpenAI has.
|
| I realize there's an infinite number of ways to
| accomplish this that would be more complex. What I was
| stating is the simplest possible way being pure prompt
| engineering. You could even try with OpenAI right now, I
| didn't try.
| joshuarrrr wrote:
| Mistakes happen: https://apnews.com/article/ncaa-
| portland-3point-line-d78742b...
| quantadev wrote:
| good example.
| mst wrote:
| > Also, maybe in future someone will optimise the route using
| that currently unused hold four down from the top?
|
| This reminds me a lot of how Brood War meta changes as new 'bugs'
| are discovered, since the fandom loves the game without it ever
| being touched so when edge cases are discovered they become part
| of the game rather than something to be fixed.
| CoreDumpling wrote:
| This week in 1945, an off-by-one error disrupts the surrender
| ceremony ending World War II:
| https://www.theglobeandmail.com/news/world/how-a-canadians-m...
| dustincoates wrote:
| > When the Japanese delegation protested - could they accept a
| botched surrender document?
|
| For some reason I find this a bit humorous. My dudes, you do
| not have much leverage.
| fracus wrote:
| Seems bizarre to keep the same wall config for all of time. The
| sport becomes about muscle memory more than anything else. The
| competitors can literally turn off their conscious brain. It
| would seem to me, it would be more exciting as a spectator and
| competitor if they had to problem solve on their way up there.
| Records could be less about best times and more about how many
| rounds did someone win in a row or something.
|
| They could even still incorporate the one standardized wall
| config as a speed round once in a while or integrate it into the
| competition in some other way.
| francis-li wrote:
| The same wall config is only for the speed competition. There
| has been debate about changing it though, cause like you said
| they become muscle memory and hyper-optimized.
|
| There are other forms of competition:
|
| - bouldering: how many of 4 short boulder problems can you
| finish
|
| - lead: how high can you get on a longer, higher route
| (pictured on the right of the image in the article)
|
| In these ones the problems are switched up every competition.
| carlmr wrote:
| This is also why every climber complained about speed
| climbing being a part of the climbing competition in the
| previous Olympics.
|
| It's an entirely different discipline. Seeing lead climbers
| compete in speed climbing is like seeing Eliud Kipchoge
| matched up with Usain Bolt for sprinting.
|
| Boulder and lead are at least somewhat related, although I
| still think it would be nice to see separate competitions
| here, too.
| Sander_Marechal wrote:
| I hope they do split up bouldering and lead next olympics.
| At least for Ai Mori's sake!
| spuz wrote:
| Indeed they will separate them at the 2028 LA Olympics.
| There will be 3 separate medals for boulder, lead and
| speed.
| KaiserPro wrote:
| > This is also why every climber complained about speed
| climbing
|
| not every climber. Its clearly a different discipline.
| Thats why boldering/lead is separate from speed climbing.
|
| But then lead is different to top rope and sport different
| to trad. And indoor is very different to outdoor.
| carlmr wrote:
| > not every climber. Its clearly a different discipline.
| Thats why boldering/lead is separate from speed climbing.
|
| It wasn't separate in the previous Olympics, that's my
| point.
|
| >But then lead is different to top rope and sport
| different to trad. And indoor is very different to
| outdoor.
|
| Except for trad most climbers I know do a mix of all of
| these.
|
| Speed climbing is just so different from everything else
| that I don't even know one climber out of the hundred or
| so that I know that does it regularly.
| ebiester wrote:
| I do think it'd be amazing to see a "decathlon-like"
| competition where runners were measured in the 100, 1500,
| and 10k cross country, though. Figuring out how to even it
| out would be a chore, though.
| lostlogin wrote:
| > Seems bizarre to keep the same wall config for all of time.
| The sport becomes about muscle memory more than anything else.
|
| Plenty of other sport are pretty much the same each time,
| particularly track and field.
| Miraltar wrote:
| Exactly, I don't understand people who watch any of the tracl
| and field disciplines and complain about this wall being the
| same everytime. Like there's about 10 different disciplines
| of people running on a plain track and that's fine but people
| climbing the same wall isn't. I totally get that you might
| find lead or bouldering more interesting but that's not the
| point.
| LeonB wrote:
| Once an activity has become a "competitive sport" it has a way
| of prioritising "measurable" over meaningful or enjoyable. When
| you develop a critical eye for this aspect of sport, the
| Olympics stop being enjoyable and become an utter horror of
| human maladjustment, a horrid parody of what it alleges to
| stand for.
| yallpendantools wrote:
| I don't watch this event but, coming from other sports, I think
| there's more to this than sheer muscle memory. Humans are not
| machines. Sometimes you compete with ongoing or lingering
| injuries. Conditioning changes even for the most disciplined of
| athletes. All of these mean that a different approach might be
| warranted for each event depending on your "set-up".
|
| Not to mention other variables outside of the human body.
| Perhaps the type of rope could matter in your performance. The
| age of the holds could matter too; even when the governing body
| standardizes on a replacement period for holds, I'm sure
| competitors would have strong opinions about the difference
| between a hold at the start of its service life versus one
| about to be replaced.
|
| Also, the one thing I love seeing in physical contests is how
| competitors eke out the last bit of performance advantage with
| sheer willpower. Muscle memory takes care of the actions but
| performance and willpower is a conscious effort.
|
| In short, no, I don't think competitors can literally turn off
| their conscious brain and just let muscle memory take over. If
| a field has jargon, there's a hell lot to geek over it.
| tway_GdBRwW wrote:
| And in further support of what you are saying, when I'm in
| the flow state, either for programming or for workout or for
| other hobbies, I am not conscious. That's kind-of the
| definition of flow.
|
| or people who describe an expert as someone who is
| unconsciously competent, they no longer have to think about
| what they are doing they just "know".
|
| And as yallpendantools is saying, operating at that level of
| expertise is much much more than sheer muscle memory, though
| the muscle memory is critical. My typing skill certainly
| helps me find flow in my programming work, I don't have to
| think about how to type each letter, when I'm in flow the
| ideas "just appear" on the screen.
|
| So rather than saying the competitors turn off their
| conscious brain, maybe it is better to say that they
| transcend it?
| devnullbrain wrote:
| >as a ... competitor
|
| Are you?
| polynomial wrote:
| How is this an off BY ONE error? (Pretty sure it's not.)
| yallpendantools wrote:
| > The fourth hold from the top in the right hand lane was _off
| by one_ with respect to its counterpart in the left hand lane.
| crote wrote:
| The grips are placed on a grid. It was supposed to be at, say,
| (43,55) but actually placed at (42,55).
| Aardwolf wrote:
| While that's indeed literally off by one, typically in
| programming an off by one error is a fence post error: if you
| have 4 fence posts, there are 3 sections in-between the fence
| posts, and off by one errors are about mistaking those two
| things. That's not really what happened in this climbing grip
| coordinates scenario here.
| KaiserPro wrote:
| I realise that by arguing the semantics, and am making this
| worse.
|
| However
|
| Off by one is the error, not the cause. sure, a lot of off
| by one errors are caused by index starting confusion, but
| not all. The hold is clearly off by one. thus its a "real
| life" off by one error.
| autarch wrote:
| > Maybe when the record is unbeaten for more than a couple of
| years they should throw it all away and start with a brand new
| route?
|
| There's been some discussion of having new speed routes every few
| years. I think this would make the event a thousand times more
| interesting. That said, I'm still not sure I'd be interested.
| Miraltar wrote:
| It would be terrible from an athlete perspective
| zelos wrote:
| How about a route pool like an esports map pool?
| devnullbrain wrote:
| There's a misconception that a quadrennial sports festival.
| Actually, they're a quadrennial festival for people who never
| cared about the sport before to explain how it should be fixed.
| whycome wrote:
| QGM
| PeterStuer wrote:
| Little known trivia: the code that won the RSA rc5 56bit
| challange had an off by 1 error.
|
| https://archive.nytimes.com/www.nytimes.com/library/cyber/we...
| Anunayj wrote:
| Where was the off by one error? I read the article and didn't
| find any mention of it.
| PeterStuer wrote:
| I haven't seen it reported anywhere. It was my machine that
| found the key. To commemorate the event a plaque was made and
| permanently attached to the case. If it is still in the
| archives somewhere, the plaque lists the key reported as
| found by the client, which you would see is one off from the
| actual key that was the solution.
|
| I never asked the distributed.net team, but I always
| suspected this was intentional to maybe thwart people from
| front-running a submission, so not truly a bug. If Adam, Jeff
| or David read this, maybe they could chime in.
| actionfromafar wrote:
| https://www.formulanon.com/movement/mrhp8j3hijw97sdl1krno2el...
| leejo wrote:
| If you're curious about those, they're all photos of the
| various sporting events that happen in the village here. All
| the effects you see are captured in camera through movements or
| otherwise.
| dwighttk wrote:
| >The kicker is that the out of place hold hasn't been used in a
| long time.
|
| I'm guessing the belay rope issue was real and the actual cause
| of the other lane always winning then.
| philip1209 wrote:
| That's funny.
|
| I discovered an off-by-one error in college as I was graduating.
| Apparently the "class plan" I had put together with an advisor
| during my second year was missing a class, and I discovered it as
| I petitioned it for graduation. "You're one class short."
|
| (It was for my second major, not the primary one, and the head of
| the physics department was nice enough to credit a nonlinear
| optimization course from engineering toward the major, so I
| earned it.)
| tomrod wrote:
| I had a similar experience in getting a Math BS after finishing
| an Econ BA (which, for my school, was notoriously short and was
| not seen as sufficient to prepare you for economics graduate
| work).
|
| The deal with my Math dept head was I had to make it my primary
| major (no true doubles at my weird undergrad, had to have an
| "additional"). It was a deal I was happy to make if it meant
| skipping an intro-to-proofs course after having taken the
| masters level series in most the of the fields they offered!
| NeoTar wrote:
| In terms of real-life off-by-one errors, it's hard to beat the
| town of Wemding in Bavaria (Germany).
|
| Here a pyramid of 120 blocks is planned, with one placed every
| ten years. It started on the 1200th anniversary of the town, and
| is planned to be complete 1200 years later... and I'm sure you've
| spotted the problem.
|
| Matt Parker, the 'stand-up Mathematician' has a video on it:
| https://youtu.be/FAdmpAZTH_M?si=_u8fM-fprUWiEqZ9
| 10-22-38Astoria wrote:
| My favorite off by one error is that the index of a count down is
| always one less than the amount that you subtracted. This means
| if you count up and down at the same time, you won't count the
| middle number twice.
|
| 1: 1, 10 :0
|
| 2: 2, 9 :-1
|
| 3: 3, 8 :-2
|
| 4: 4, 7 :-3
|
| 5: 5, 6 :-4
|
| Since the sum on each line is 11, the sum of all the numbers from
| one to ten is 55.
|
| The cool thing is that this generalizes
|
| 1: 1, N : 0
|
| 2: 2, N - 1 :-1
|
| 3: 3, N - 2 :-2 <-sum is N+1
|
| ...
|
| N/2: N/2, N -(N/2)+1 => N/2+1
|
| So the sum of N numbers is N/2 * (N/2+N/2+1) => N/2 * (N+1) if N
| is even.
|
| It appears to be broken for odd numbers
|
| 1: 1, 9 :0
|
| 2: 2, 8 :-1
|
| 3: 3, 7 :-2
|
| 4: 4, 6 :-3
|
| 5: 5, 0 :-4 <- can't reuse 5
|
| But for odds, setting the odd number K equal to N+1, N is an even
| number so the total sum is sum(N) + N+1. We showed that sum(N) =
| N/2 *(N+1). So we have N/2 * (N+1) + (N+1).
|
| But that means N/2+1 * (N+1) equals sum(K)
|
| => (N+2)/2 * (N+1)
|
| => (K+1)/2 * K
|
| So the formula N/2 * (N+1) computes the sum of N numbers if N is
| odd too! It works for all numbers. Wow!
|
| [Edit: Formatting]
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