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In a programming contest, I forgot how to round numbers in Java, an I needed a 3 number rounding, so I multiplied the number by 1000, then sum 0.5 and convert it to integer so the decimal part would be gone, finally, just print the number except the 3 last digits as a string, put a period and print the other 3 digits.
I must say I'm not proud of that.5 -
POSTMORTEM
"4096 bit ~ 96 hours is what he said.
IDK why, but when he took the challenge, he posted that it'd take 36 hours"
As @cbsa wrote, and nitwhiz wrote "but the statement was that op's i3 did it in 11 hours. So there must be a result already, which can be verified?"
I added time because I was in the middle of a port involving ArbFloat so I could get arbitrary precision. I had a crude desmos graph doing projections on what I'd already factored in order to get an idea of how long it'd take to do larger
bit lengths
@p100sch speculated on the walked back time, and overstating the rig capabilities. Instead I spent a lot of time trying to get it 'just-so'.
Worse, because I had to resort to "Decimal" in python (and am currently experimenting with the same in Julia), both of which are immutable types, the GC was taking > 25% of the cpu time.
Performancewise, the numbers I cited in the actual thread, as of this time:
largest product factored was 32bit, 1855526741 * 2163967087, took 1116.111s in python.
Julia build used a slightly different method, & managed to factor a 27 bit number, 103147223 * 88789957 in 20.9s,
but this wasn't typical.
What surprised me was the variability. One bit length could take 100s or a couple thousand seconds even, and a product that was 1-2 bits longer could return a result in under a minute, sometimes in seconds.
This started cropping up, ironically, right after I posted the thread, whats a man to do?
So I started trying a bunch of things, some of which worked. Shameless as I am, I accepted the challenge. Things weren't perfect but it was going well enough. At that point I hadn't slept in 30~ hours so when I thought I had it I let it run and went to bed. 5 AM comes, I check the program. Still calculating, and way overshot. Fuuuuuuccc...
So here we are now and it's say to safe the worlds not gonna burn if I explain it seeing as it doesn't work, or at least only some of the time.
Others people, much smarter than me, mentioned it may be a means of finding more secure pairs, and maybe so, I'm not familiar enough to know.
For everyone that followed, commented, those who contributed, even the doubters who kept a sanity check on this without whom this would have been an even bigger embarassement, and the people with their pins and tactical dots, thanks.
So here it is.
A few assumptions first.
Assuming p = the product,
a = some prime,
b = another prime,
and r = a/b (where a is smaller than b)
w = 1/sqrt(p)
(also experimented with w = 1/sqrt(p)*2 but I kept overshooting my a very small margin)
x = a/p
y = b/p
1. for every two numbers, there is a ratio (r) that you can search for among the decimals, starting at 1.0, counting down. You can use this to find the original factors e.x. p*r=n, p/n=m (assuming the product has only two factors), instead of having to do a sieve.
2. You don't need the first number you find to be the precise value of a factor (we're doing floating point math), a large subset of decimal values for the value of a or b will naturally 'fall' into the value of a (or b) + some fractional number, which is lost. Some of you will object, "But if thats wrong, your result will be wrong!" but hear me out.
3. You round for the first factor 'found', and from there, you take the result and do p/a to get b. If 'a' is actually a factor of p, then mod(b, 1) == 0, and then naturally, a*b SHOULD equal p.
If not, you throw out both numbers, rinse and repeat.
Now I knew this this could be faster. Realized the finer the representation, the less important the fractional digits further right in the number were, it was just a matter of how much precision I could AFFORD to lose and still get an accurate result for r*p=a.
Fast forward, lot of experimentation, was hitting a lot of worst case time complexities, where the most significant digits had a bunch of zeroes in front of them so starting at 1.0 was a no go in many situations. Started looking and realized
I didn't NEED the ratio of a/b, I just needed the ratio of a to p.
Intuitively it made sense, but starting at 1.0 was blowing up the calculation time, and this made it so much worse.
I realized if I could start at r=1/sqrt(p) instead, and that because of certain properties, the fractional result of this, r, would ALWAYS be 1. close to one of the factors fractional value of n/p, and 2. it looked like it was guaranteed that r=1/sqrt(p) would ALWAYS be less than at least one of the primes, putting a bound on worst case.
The final result in executable pseudo code (python lol) looks something like the above variables plus
while w >= 0.0:
if (p / round(w*p)) % 1 == 0:
x = round(w*p)
y = p / round(w*p)
if x*y == p:
print("factors found!")
print(x)
print(y)
break
w = w + i
Still working but if anyone sees obvious problems I'd LOVE to hear about it.38 -
#LongRant
I AM SO FUCKING PISSED RIGHT NOW OF ALL YOU DICKHEADS WHO DON'T KNOW SHIT 'BOUT PROGRAMING AND STILL QUALIFY FOR THE NEXT ROUND!
Background: I am a final year student of Computer Science. This time of the year, companies come to the campus to recruit potential employees for their vacant positions. But during the COVID-19 times, the number of such companies and jobs have gone a little down. Two companies came to our university for recruitment — DXC Technology and Hanu Software. I cleared the aptitude/code test for DXC and appeared for the interview, which went fairly well. Waiting on the results. The rant is about the other company.
The Story: I am learning and working on Cloud (AWS specifically) for the past 1 year. I have a cloud Certification in Oracle and working my way to get Azure Certified. Hanu Software, which is a core cloud company (works on Azure) came to our campus for the recruitment (Cloud Engineer). Their test had these sections —
1. Personality (54 Questions; 15 minutes)
2. Verbal (20 Questions; 20 minutes)
3. Reasoning (15 Questions; 15 minutes)
4. Technical (25 Questions; 25 minutes)
5. Quantitative (15 Questions; 15 minutes)
As soon as I finished my Interview with DXC, I had my Hanu test within 30 minutes. I have a Mac so the test by default started on Safari. After completing 4 sections, I receive a mail in Junk from Hanu which stated that only Chrome or Firefox can be used to give the test. AHH! And on Safari.. the platform on which the test was being conducted didn't ask me for any camera permission (the test is monitored, can't even change windows/switch tabs). I then changed the browser to Mozilla Firefox and somehow finish the test. After finishing, I call up my classmates to find out how their test go. Know what? FUCKING TWATS USED GOOGLE LENS TO FIND OUT THE ANSWERS!
Last night, the list of qualifying students arrived and obviously I didn't make it to the list, but those dumbfucks did who don't even know what Cloud technology is or how it works. Neither they could do any average level program, nor have the communication skills. HOW?! HOW THEM AND NOT ME? Life is very unfair sometimes. I couldn't sleep at night.
PS: If you made this far, thank you for reading this rant (and sorry for it being so long). Makes it better to be able to share with someone. If you could, then please guide me (online resources/recommendations) to be better at competitive programming, or help me enhance my resume/linkedin or if you could refer me for an entry level position at your organisation, I would eternally be grateful. Thank you once again. And sorry for the long rant.17 -
I just realized why you should never help people with tech problems, at least for free.
I went to grab the rent from a family that lives in my grandma's childhood home.
The father asks me if I could have a look at their new internet connection because it doesn't open any pages on the browser.
After fiddling for about an hour and a half trying every trick in the book and gently explaining to his children how everything is supposed to work (kids need to learn how these machines work imho) I ask him to give me his service provider number and confirmed that indeed the problem was that the connection wasn't activated on their side. Installed chrome, set the date,/time because it wouldn't sync and told them twice how to get past the certificate problem should some page not open. Smiles all around, all is well.
Fast forward next to next morning and I get a call from the guy telling me his internet doesn't work because he pulled out the power cable for whatever reason. I instruct him to restart the router just to be sure and then ask him what's on the screen. Turns out it was the certificate problem. I try as best I can explaining and reminding him how to get past but he doesn't understand. He goes on asking me to "come over for 5minutes and have a look at it". I politely tell him that just the trip is half an hour and that I am currently in the middle of exams to finish university. His tone becomes increasingly passive aggressive as I tell him again that it's isn't possible for me to make the time for a one hour round trip at the moment. Hangs up with a grim "right right whatever you say."
First time I was genuinely angry at a person being both so ungrateful after helping them and not even trying to fix something after I took the time to explain it to them.10 -
Manager: "Can we get an accurate report on how many containers we have on the Kubernetes cluster?"
Me: "Well not really since Kubernetes is designed to be dynamic and agile with the number of resources and containers being created and deleted being subject to change at a moment's notice."
Manager: "I want numbers"
Me: "Okay well if we look at a simple moving average over time, we can see how the number of containers changes and then grab a rough answer from that"
Manager: "These numbers look a little round, are you sure these are exact?"
I'm going to throw myself into a pile of used heroin needles and hope i get stuck with whatever the hell this guy has to somehow be a manager while also being this retarded.15 -
While working on my one of the first project in java i ended up using deprecated Calendar API for the date. Since deadline was near i thought it would be a good idea to use the JCalendar API for as date picker (which is a third party API).BAD IDEA. It was the night before the submission round about 11pm when i realized that there is no way to convert JCal object into Calendar and it turned out it is not working as expected you have to subtract a particular number from the year to get date right.
To convert JCal into Calendar i used the toString function to get the date in string sliced it using substring into year,month,day then had to assign date to Calendar object via constructor.
Had to write 70 lines of code just to convert JCal into Calendar...
And then there were other complications related to this problem. Had tu pull an all nighter just to solve date related problems
LESSONS LEARNED :
NEVER USE A DEPRECATED API
NEVER USE THIRD PARTY APIs WITHOUT RESEARCH
7 -
So, today's comedy job story (and how depressive things become), and it's only 9:30.
Stressed PM assaults me at 8 to tell me what I have to do, standing next to me and dictacting stuff she wants done. Hate that.
As I went to a colleague to help her out with these fucking presentations (she "couldn't open them"), as I just arrived to her office my phone rings.
It's my PM. I'm 20m away, she calls me. Ok.
Me: "Yes?"
PM: "Hey Phlisg, erm, we are stuck in a conference room, can you come and open the door?"
Me: "Erm, the door has no handle, can't help"
PM: "Can you call the "housekeeper"?"
Me: "Sure" (why the hell doesn't she have his number...)
I go downstairs, go towards the conference room, and before the door there is the reception office. I ask the colleagues in there if the "housekeeper" is here, but they instead produced the handle from their drawers, and went to the door to open it.
At the same time, a person locked inside the conference room went through the window to go round and try to open the door.
Door successfully opened by colleague with handle.
I mean...
WHAT
THE
FUCK!
You have a problem? One reflex: call Phlisg. She might call me at 2 am in the morning because she cannot sleep or something.
Pissed!!13 -
What grinds my gears:
IEEE-754
This, to me, seems retarded.
Take the value 0.931 for example.
Its represented in binary as
00111111011011100101011000000100
See those last three bits? Well, it causes it to
come out in decimal like so:
0.93099999~
Which because bankers rounding is nowstandard, that actually works out to 0.930, because with bankers rounding, we round to the nearest even number? Makes sense? No. Anyone asked for it? No (well maybe the banks). Was it even necessary? Fuck no. But did we get it anyway?
Yes.
And worse, thats not even the most accurate way to represent
our value of 0.931 owing to how fucked up rounding now is becaue everything has to be pure shit these days.
A better representation would be
00111101101111101010101100110111 <- good
00111111011011100101011000000100 < - shit
The new representation works out to
0.093100004
or 0.093100003898143768310546875 when represented internally.
Whats this mean? Because of rounding you don't lose accuracy anymore.
Am I mistaken, or is IEEE-754 shit?4 -
finally...a nice round number of ++, hopefully they use more than an unsigned 8 bit otherwise I'm gonna overflow after this post! :P
1 -
How do I help my colleague in fighting harrassment?
This is the story of a helpless employee facing everyday harassment. Im trying to help. Seeking for your thoughts
Backstory fast forwarded: My company acquired another company. So we handle all their projects and clients now, but its a completely new domain. So we needed new people. Hired 4 employees + 1 team lead to start with. But the project process got delayed and they were free for a month. So i took 2 of them in my project and gave them some small tasks to help us over. They loved working with my team and were learning new stuff apart from what they usually did. And we were also happy of their contribution. We became good friends. All of this was in March 2020 before covid-19 was taken seriously.
About my company: I love this company. I have been in this company for more than 4 years now. People are really nice. Parties and fun events. Lot of smart and ambitious people. So company and people are awesome.
Coming back to the story. Lets call the team the 4 and team lead T. The 4 were happy that someone like T was in their team. This T had all the best knowledge about stuff and life was going to be awesome for the 4. Or was it?
Story starts: So I talk to one of these 4 on daily basis. Lets call this friend F. F is a real gentle person. Intelligent and dedicated to work. F is awesome to work with. And always enjoyed working. F is a team player and very very soft person. F is fking workoholic. So few days after project starts, F tells me work was not going well. F is getting real frustrated at work and not able to deal with it or find solution.
What happened:
This person T, who was supposed to help these 4, is real piece of shit. He is impatient, arrogant and MFing dick head. Aaaarggggg.
All the good qualities of a leader like supporting the team, boosting confidence, guiding team when they make mistakes, teaching them, were all missing from this person. T was a machine with no emotion and only clock working jerk. I have no idea how T cleared interview process, because one of the interview round is also about cultural fit into company. I know this because i take interviews for other domains. We have rejected lot of such well qualified but arrogant candidates.
So whats the problem now: this team of 4 are learning new tools and taking over the clients requests from old company. Most of the stuff is new for them. So in tat case people need lot of time to understand and figure out shit. people make mistakes while learning and you know have to deal with it. Person T abuses these 4 when something goes wrong. That's one.
Second, the T definitely knows more than these 4. So if these guys dont understand certain stuff they ask T. But T does not help them learn. T will either say busy or run away by saying thats simple and ull know when time comes. REALLY MF???
Third, T does not talk nice. T is rude and does not listen to team members. For eg, If F says some task cannot be done for some reason T will say, "y cant u do it? U r capable of doing it. Tats y u r in this job". And then point number one and two happens. Never responds to emails and messages. But if someone else does the same will not tolerate that and abuses them. List goes on.
So y not escalate and deal with that T:
This person F and other 3 are still under probation and they think complaint or escalation will back fire. These people do not want to lose job in between all this pandemic shit. They are scared.
So this was happening for a while. And i was giving lot of tips on how to handle certain situations. And how one should communicate these.
But being a gentle, soft and workoholic person, F focussed on work and assumed things will get in place as time goes by.
Today, F could not meet a requirement. So T told some shit which got F all sad. and F called up me late night and started crying explaining what happened. I felt real bad. I asked F to file harrassment case. F refused saying it was F's mistake on not completing requirement. WHO THE FK CARES. PEOPLE CANNOT TALK SHIT. I told ill file harrassment case against T. (We have a policy where others can also file if person is not courageous enough). But F did not allow me.
Then after calming down, I told F that telling the problems to me wont solve them. You have to talk to T directly and tell him on face not to talk like this. Or tell the manager about whats happening. Or tell the the HR about this. F said tat cant be done. I was like Y THE FK NOT.
Because the other 3 are not ready to talk about this to anyone as they fear they'll lose job. So if F talks and people question other 3 they might bail out. WAT THE HOLY SPIRIT.
so after lot of convincing F is still not going to
Talk to anyone about this.
So i have decided ill write an anonymous email to HR, the manager and other senior people in the organisation about whats happening.
I really dont know how itll go. Ill keep updating you guys. Feel free to share ur thoughts.3 -
When a project manager files a bug report:
"does not match the mockup.
See G:///Departments/Digital/...(client name)/(job code)/(project number)/creative/mockups/round 4/final/final 2/final_(date)/final-(date)_v5.psd"2 -
Having this trend we should plan for log4j 2.18 release 'round Wednesday-Thursday.
By the EOY we're likely to reach 2.22. That's a nice version number to meet 2022 with :)
v2.0222 -
I called the hack "blow up bunny", was in my first company.
We had 4 industrial printers which usually got fed by PHP / IPP to generate invoices / picking lists / ...
The dilemma started with inventory - we didn't have time to prepar due to a severe influenza going round (my team of 5 was down to 2 persons, where on was stuck with trying to maintain order. Overall I guess more than 40 % ill, of roughly 70 persons...)
Inventory was the kind of ultimate death process. Since the company sold mobile accessoires and other - small - stuff.
Small is the important word here....
Over 10 000 items were usually in stock.
Everything needed to be counted if open or (if closed) at least registered.
The dev task was to generate PDFs with SKUs and prefilled information to prevent disaster.
The problem wasn't printing.
The problem was time and size.
To generate lists for > 10 000 articles, matching SKUs, segmented by number of teams isn't fun.
To print it even less. Especially since printers can and will fail - if you send nonstop, there is a high chance that the printer get's stuck since the printers command buffer get's cranky and so on.
It was my longest working day: 18 hours.
In the end "Blow up bunny" did something incredibly stupid: It was a not so trivial bash pipeline which "blew up" the large PDF in a max of 5 pages, sent it to one of the 4 printers in round robin fashion.
After a max of 4 iterations, bunny was called.
"bunny" was the fun part.
Via IPP you can of course watch the printer queue.
So...
Check if queue was empty, start next round with determined empty printer queues.
Not so easy already. But due to the amount of pages this could fail too.
This was the moment where my brain suddenly got stuck aft 4 o clock in the morning in a very dark and spookey empty company - what if the printer get's stuck? I could send an reset queue or stuff like that, but all in all - dead is dead. Paper Jam is paper jam.
So... I just added all cups servers to the curl list of bunny.
Yes. I printed on all > 50 printers on 4 beefy CUPS servers in the whole company.
It worked.
People were pretty pissed since collecting them was a pita... But it worked.
And in less than 2 hours, which I would have never believed (cannot remember the previous time or number of pages...)1 -
The bug: Some string values for an identifier property in the data objects are being sent from our frontend prefixed with a '0'. Sometimes. When it happens, it usually gets stripped away again by the time it's passed to our backend. But not always.
This 0 is never explicitly set anywhere. I even searched for a few variants of " = 0" in both the frontend and backend projects without receiving any results. You might already be suspecting where this is going.
So it turns out.
The data object which holds this value is being initialized in the aspnet (don't ask) backend and passed to the frontend, which then hydrates it. This value is always an integer number, albeit incidentally so which is why string is used as the actual type. When this object is initialized, it's hardcoded with an anonymous type where this property is set as int because I guess someone figured "it's always an int though". Being a typed language, primitive scalars can't be null objects which means the property's value becomes the concrete int 0.
Okay weird. I can think of better ways of doing this but let's just set it to string as I can't start overhauling things right now. Let's just go find where this value is somehow concatenated into the incoming parameter.
You see, this happens because at the point where the frontend sets this value, it may be an int or string depending on where it came from, and I guess someone figured that in order to cast it to string you just go prop += arg seeing as the prop is empty string and all. Because explicitly casting it or - as much as I get a rash whenever I see it - going prop = "" + arg would be too verbose and unoriginal.
Bonus round: How come the 0 only sometimes made it all the way to our backend? The thing is that this bug has been fixed before. The fix is that because this string is "always" an int, you can parse it to int before passing it to the backend in case it has leading zeroes. This path is only taken in certain views because someone forgot to copypaste their fix into all the places this is repeated.
Sometimes you find a bug and you are just somehow more grumpy after fixing it.1
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