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Two big moments today:
1. Holy hell, how did I ever get on without a proper debugger? Was debugging some old code by eye (following along and keeping track mentally, of what the variables should be and what each step did). That didn't work because the code isn't intuitive. Tried the print() method, old reliable as it were. Kinda worked but didn't give me enough fine-grain control.
Bit the bullet and installed Wing IDE for python. And bam, it hit me. How did I ever live without step-through, and breakpoints before now?
2. Remember that non-sieve prime generator I wrote a while back? (well maybe some of you do). The one that generated quasi lucas carmichael (QLC) numbers? Well thats what I managed to debug. I figured out why it wasn't working. Last time I released it, I included two core methods, genprimes() and nextPrime(). The first generates a list of primes accurately, up to some n, and only needs a small handful of QLC numbers filtered out after the fact (because the set of primes generated and the set of QLC numbers overlap. Well I think they call it an embedding, as in QLC is included in the series generated by genprimes, but not the converse, but I digress).
nextPrime() was supposed to take any arbitrary n above zero, and accurately return the nearest prime number above the argument. But for some reason when it started, it would return 2,3,5,6...but genprimes() would work fine for some reason.
So genprimes loops over an index, i, and tests it for primality. It begins by entering the loop, and doing "result = gffi(i)".
This calls into something a function that runs four tests on the argument passed to it. I won't go into detail here about what those are because I don't even remember how I came up with them (I'll make a separate post when the code is fully fixed).
If the number fails any of these tests then gffi would just return the value of i that was passed to it, unaltered. Otherwise, if it did pass all of them, it would return i+1.
And once back in genPrimes() we would check if the variable 'result' was greater than the loop index. And if it was, then it was either prime (comparatively plentiful) or a QLC number (comparatively rare)--these two types and no others.
nextPrime() was only taking n, and didn't have this index to compare to, so the prior steps in genprimes were acting as a filter that nextPrime() didn't have, while internally gffi() was returning not only primes, and QLCs, but also plenty of composite numbers.
Now *why* that last step in genPrimes() was filtering out all the composites, idk.
But now that I understand whats going on I can fix it and hypothetically it should be possible to enter a positive n of any size, and without additional primality checks (such as is done with sieves, where you have to check off multiples of n), get the nearest prime numbers. Of course I'm not familiar enough with prime number generation to know if thats an achievement or worthwhile mentioning, so if anyone *is* familiar, and how something like that holds up compared to other linear generators (O(n)?), I'd be interested to hear about it.
I also am working on filtering out the intersection of the sets (QLC numbers), which I'm pretty sure I figured out how to incorporate into the prime generator itself.
I also think it may be possible to generator primes even faster, using the carmichael numbers or related set--or even derive a function that maps one set of upper-and-lower bounds around a semiprime, and map those same bounds to carmichael numbers that act as the upper and lower bound numbers on the factors of a semiprime.
Meanwhile I'm also looking into testing the prime generator on a larger set of numbers (to make sure it doesn't fail at large values of n) and so I'm looking for more computing power if anyone has it on hand, or is willing to test it at sufficiently large bit lengths (512, 1024, etc).
Lastly, the earlier work I posted (linked below), I realized could be applied with ECM to greatly reduce the smallest factor of a large number.
If ECM, being one of the best methods available, only handles 50-60 digit numbers, & your factors are 70+ digits, then being able to transform your semiprime product into another product tree thats non-semiprime, with factors that ARE in range of ECM, and which *does* contain either of the original factors, means products that *were not* formally factorable by ECM, *could* be now.
That wouldn't have been possible though withput enormous help from many others such as hitko who took the time to explain the solution was a form of modular exponentiation, Fast-Nop who contributed on other threads, Voxera who did as well, and support from Scor in particular, and many others.
Thank you all. And more to come.
Links mentioned (because DR wouldn't accept them as they were):
https://pastebin.com/MWechZj912 -
Recently I launched the minimalistic online drawing app https://okso.app. I wanted it to be a place where people could do fast, ad-hoc, napkin-based-like explanations of any concept as if you are sitting with your friend and trying to explain him/her something during lunch. Don't ask me why it is needed, I was just experimenting.
So, the first concept I've tried to explain with sketches was the Data Structures. Without further ado, here is the interactive ✍🏻 https://okso.app/showcase/... showcase that you may play with.
Of course, not all data structures are covered. And of course, this is not comprehensive material, but rather a cheatsheet that would create visual hints and associations for the following data structures:
- Linked List
- Doubly Linked List
- Queue
- Stack
- Hash Table (with hash collision resolution)
- Tree (including the Binary Search Tree)
- Heap (including Mean Heap and Max Heap)
- Trie
- Graph
Each box on the sketch is clickable, so you may dig into the data structure you're interested. For example `Heap → Max Heap`, or `Heap → Min Heap`, or `Heap → Array Representation`.
The sketches are split into so-called Pages just to make it easier to grasp them, so the users stay focused on one concept at a time, they see the relationship between the concept, and thus, hopefully, they are not getting overwhelmed with seeing a lot of information at the same time on one drawing/page.
Each page has a link to the source-code examples that are implementing the data structure on JavaScript.
The full list you may find in the ✍🏻 https://okso.app/showcase/... showcase.
I hope you find this showcase useful and I hope it will be a good visual cheatsheet-like complement to your data structure knowledge.
12 -
I’ve been looking for a job recently since I am a student and starting my career.
I have a bunch of experience and I like to think I have pretty broad knowledge of programming concepts (web dev, ML, AI, software development).
I see these job postings for jobs that I know I am qualified for.
- I got my research published (which is related to the jobs I’ve been applying for)
- I have great grades
- I have a clear track record of doing well in teams (life long athlete)
- I am a complete geek for new tech and libraries so I always learn them super fast
- I have side projects that aren’t just shit I’ve done in school
- my past jobs show that I am an efficient worker who has real experience
However, I always fucking fail the coding challenges.
I’m never asked questions like “how to reverse a linked list”, just obscure questions that I don’t know how to study for.
What the fuck am I supposed to do? It’s not even like I get close to the answers. I usually get a couple test cases and then fail the rest of them, or I can’t figure out a solution to solve them.
This is all really disheartening and I fucking hate it I absolutely fucking hate it and when I am trying to hire people in the future, I’m never going to make them do coding challenges bc they’re fucking stupid4
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