Opinion on Henri Cohen’s Number Theory books [on hold]

I am a graduate student willing to learn Number Theory. I have come across Henri Cohen’s “Number Theory” (Vol. I and II) and I would like to hear from someone who has read these books before: are they comprehensive and clear? Is there any particular topic which is not so well covered? I apologize if the question seems vague but any comments regarding these books would be appreciated.

Which book or books are being used in these lectures on Distributed Systems?

Kindly take a look at these lecture materials.

The instructor is suggesting to study books of Tanenbaum along with his supplied reading list. But, I am not finding any similarity of the content between the lectures slides and Tanenbaum‘s books and other reading materials.

Take for example the following slides from Lecture#2:

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Where are these images sourced from?

Kindly, provide me some suggestions regarding any book or additional reading material.

Apple Books app and multiple desktops: How to stop app window to show on all Desktops?

I am running macOS Mojave 10.14.4 with Books.app version 1.18.

I use multiple Desktop. When I open the Books app on one Desktop, and then switch to another Desktop, the Books app window shows on that Desktop as well.

Even worse, any open Books app window pop in front of all other windows on that Desktop.

I’ve tried assigning the Books application to a specific Desktop, to all Desktops and to None, and did not see any change in behavior.

This only happens with the Books app on my system.

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What may be potentially causing this? How can I keep Books app window restricted to a single Desktop?

Python script to scrape the prices of books from a website

I have written a Python script to get the prices of books from a website. I have used requests and BeautifulSoup for that.

I am getting ISBNs from an excel file and writing the output to a CSV file. The problem with my code is that it generates a lot of duplicates. If my excel file has 1000 ISBNs, it will get more than 100,000 ISBNs.

Here is my code:

import requests from bs4 import BeautifulSoup as bs import time from fake_useragent import UserAgent fav = 'Mozilla/5.0 (compatible; MSIE 10.0; Macintosh; Intel Mac OS X 10_7_3; Trident/6.0)' ua = UserAgent(fallback = fav) import openpyxl import csv import os import random import logging logging.basicConfig(filename='ProgramLog.log',level=logging.WARNING, format='%(asctime)s %(message)s', datefmt='%m/%d/%Y %I:%M %p', filemode='w') import multiprocessing   class Sonya:      def write(self, isbn : str, price : str):         outputFile = open('output.csv', 'a+', newline='')         outputWriter = csv.writer(outputFile)         outputWriter.writerow([f'{isbn}', f'{price}'])         outputFile.close()  ##    def getProxy(self, proxy): ## ##        htp = 'http://' + proxy ##        htps = 'https://' + proxy ## ##        proxies = { ##                  'http': htp, ##                  'https': htps, ##                } ## ##        return proxies        def main(self, isbn : str):          url = 'https://m.directtextbook.com/ourbuybacktable.php?ean=' + isbn            header = {'User-Agent':str(ua.random)} #randomizes the user-agent          #proxies = self.getProxy(proxy)          response = requests.get(url, headers=header)         res = response.text         soup = bs(res, 'html.parser')          try_again = True         tries=0         while try_again:             try:                 d,c=str(soup.find('div',{'class':'totalint'}).text).split('\xa0')                 try_again = False             except AttributeError:                 if tries<=2:                     print("Try again")                     try_again = True                     tries+=1                 else:                     try_again = False                     return          price = d+'.'+c         price = price.replace('$  ','')         print(price)          self.write(isbn, price)    #proxy_list = open('proxy.txt').read().split('\n')   def mainn(li):      try:          #proxy = random.choice(proxy_list)           for isbn in li:             try:                 #isbn = str(sheet.cell(row=i+1, column=1).value)                  s=Sonya()                 s.main(isbn)                 print(li.index(isbn))             except Exception as e:                 print(e)                 logging.warning(e)     except Exception as e:         print(e)         logging.warning(e)   if __name__=='__main__':      isbns = []     isbn_wb = openpyxl.load_workbook('isbn.xlsx')     sheet = isbn_wb.active      for i in range(sheet.max_row):         if sheet.cell(row=i+1, column=1).value != '':             isbns.append(str(sheet.cell(row=i+1, column=1).value))  ##    print(isbns)     print(len(isbns))      d={}      for i in range(20):         d[f'is_{i+1}'] = isbns[i*len(isbns)//20:(i+1)*len(isbns)//20] ##        print('--------') ##        print(isbns[i*len(isbns)//20:(i+1)*len(isbns)//20]) ##        print('--------') ##        print(d[f'is_{i+1}'])       for i in range(20):          d[f'th_{i+1}']=multiprocessing.Process(target=mainn, args=(d[f'is_{i+1}'],))        for i in range(20):         d[f'th_{i+1}'].start() 

Network flow for assigning books to boxes

I am trying to model the following problem correctly as a min-cut network flow problem. I have $ n$ books and 2 boxes. I also have books that I know must go in one of the two boxes. In addition, each book has a certain profit if I put it in the same box with another book. So for instance, if I pair book $ i$ with book $ j$ I might have a profit of 10 dollars so long as they’re in the same box. If I have 3 books in one box, I’d have to sum the profit of 1 and 2, 2 and 3, and 1 and 3. I want to find the best way to assign the not-yet assigned books to either box 1 or 2 to maximize my profit. Formally:

  • 2 boxes: $ b_1$ and $ b_2$
  • Set: $ N$ of $ 1…n$ books
  • $ S_1$ = set of all books that must go to box 1
  • $ S_2$ = set of all books that must go to box 2
  • $ p_{ij}$ = The profit by having books $ i$ and $ j$ in the same box
  • Objective (roughly): $ max(\sum_{i=1}^{2}\sum p_{ij})$ (maximize the profit over all boxes)

My ideas so far:

  • Formulate the problem as a min-cut problem because we are trying to end up with two sets of books (one for box 1, one for box 2). Would it be correct to say that $ -min(-\sum_{1}^{2}\sum p_{ij})$ is equivalent to our maximization above? I tried simplifying it further but I’m not sure how.

    • Make source node for box 1, node for each book not assigned (not in $ S_1$ and not in $ S_2$ ) and a sink node for box 2.

My question:

With the previous formulation in mind, I’m confused on what the edges would be like. I have edges from box 1 to the book nodes and then the book nodes to box 2 but I’m not sure if this makes sense, largely because I need to make sure my summation notation is correct and how to turn that into an appropriate graph. Could anyone offer advice on the minimization I wrote above and how to translate it to a graph correctly?

What books do I need to DM a 3.5 game?

I’ve DMed a few 5e D&D sessions and I’ve thoroughly enjoyed it, but I did some research and found that the more in depth nature of 3.5 seemed like something I might enjoy.

I was able to track down a comparatively well priced copy of the Players Handbook. Now my problem is that all of the other books are quite hard to find or expensive (I live in Germany so I had to import my player’s handbook to get the English copy, making the shipping costs higher than the cost of the book)

I own all of the core books for 5e and Volo’s guide, could I run a 3.5e campaign with just the player’s handbook?

Which books do I need in order to run a Starfinder game?

I recently got me the core rule book of Starfinder and I really love the setting and the rules.

I want to run a Starfinder game but I don’t exactly know which books I need or where to start exactly. I’ve looked at the books in Paizo’s web shop but I couldn’t really find out which books are needed.

E.g. there are numerous Alien Archive books. I couldn’t really find out if I only find some setting specific aliens in them or if I find more generic enemies like rabid dogs, thugs or the like. What I really like is the idea of traveling around in a starship and as far as I’ve seen I need several of the Alien Archive books in order to play in differing settings.

The Armory book seems to be a bit superfluous as mos basic gear is described in the core rules.

I know there are the published adventures that hopefully provide everything that’s needed but I think they are a bit pricey. Maybe I’ll buy them later but for now I just want to play around a bit.

Primarily I lack enemy stats and descriptions but something like the Dnd 5e Starter Box would be nice too. With some maps, miniatures and enemy descriptions. Maybe some loose guidlines.

Can someone with experience in Starfinder help me please 🙂