The h Bar

@0celouvsky In this case because the relevant building blocks to construct asymptotically cylindrical Calabi-Yau 3-manifolds apparently are semi-Fano 3-manifolds and "semi-Fano" is an algebro-geometric concept. The Calabi-Yau cylinders in turn are the essential building block to construct compact $G_2$-manifolds through twisted connected sums.

0celouvsky

christ

John Rennie

@Kaumudi.H Got it. I'll reply by mail.

ACuriousMind

@BalarkaSen Hm, yes, that makes sense

user228700

4:30 PM

@JohnRennie OK. Thank you :-)

0celouvsky

@BalarkaSen is that supposed to be $\smile$

John Rennie

@Kaumudi.H YHM

Fawad

@JohnRennie YHM means?

John Rennie

Young Hairy Mammoth

Emilio Pisanty

4:45 PM

OK, folks, here's a quiz: identify this wildly cited researcher

John Rennie

Ed Witten?

Prahar

700k citations since 2012!

I doubt even Ed Witten could amass those numbers in a span of 5 years, isn't it?

Emilio Pisanty

@JohnRennie cooooold

Prahar

i cannot think of anyone in physics who could amass that

user228700

@JohnR: I'm sorry, I'll respond in a bit...

Prahar

4:49 PM

sigmund freud, maybe

0celouvsky

Bill Nye the Science Commie

@EmilioPisanty well, who is it??

Emilio Pisanty

> The academic superstar everybody wants to be co-author with

of course

Prof. Et al.

John Rennie

Groan :-)

0celouvsky

That's an unfortunate name

He sounds like the thing you put when there are multiple authors

Emilio Pisanty

finally caught on camera, too

@0celouvsky she

0celouvsky

4:54 PM

@JohnRennie I will stop with the sheep comments if you stop the nose

@EmilioPisanty what?

John Rennie

@EmilioPisanty I thought for a moment you were going to say Erdős, but his citation score is relatively low.

Emilio Pisanty

@0celouvsky Prof. Et al is female

see the homepage

0celouvsky

That's some PC bullshit.

I'll default to female when they're the majority in science.

Emilio Pisanty

@0celouvsky Dr. A. Author is male, though

> Enter dr. A. Author. Ranking second in the field of citation analysis, his h-index is 30 and he has over 3500 citations. Among his most influential papers are “Title of article” with 159 citations and “Title of paper” with 128 citations to date. It is a matter of some regret to him that his 1990 “Instructions to authors” has been less influential, but perhaps its time is yet to come.

Bernardo Meurer

@JohnRennie @dmckee codereview.stackexchange.com/questions/159345/…

0celouvsky

4:57 PM

I can't actually find the gender

dmckee

@BernardoMeurer That's a working method, and for the size of a 2048 will never too long.

But there is a method that guarantees to choose a random empty cell in O(n) time and O(1) space, which you might prefer if the board was very large (when the stochastic method you are using has the possibility of a long running time).

Bernardo Meurer

@dmckee Oh, sweet, do tell!

dmckee

Set a counter to c=1. Walk the cells in some definite order. Every time you encounter a empty cell you (a) set the selected cell to the current cell with probability 1/c, and (b) increment c. When you have exhausted the cells simply use the selected cell.

Bernardo Meurer

Hmm

dmckee

This use case is a little more complicated than usual because some cells are empty and some are not, but this is also the algorithm used to chose elements of a list (or other data structure with sequential rather than random access) randomly with equal probability.

So I had to jigger it a little to ensure that you select some cell (the first empty one you encounter).

John Rennie

5:05 PM

void randCell(int _board[BOARD_SIZE][BOARD_SIZE]) {
    int row;
    int col;
    int num_empty = 0;
    int empty[BOARD_SIZE*BOARD_SIZE];

    // Check if there's any empty spaces
    for (int i = 0; i < BOARD_SIZE; ++i) {
        for (int j = 0; j < BOARD_SIZE; ++j) {
            if (_board[i][j] == EMPTY) empty[num_empty++] = i*BOARD_SIZE+j;
        }
    }

    if (num_empty > 0) {
        int random_cell = randRange(0, num_empty)
        col = empty[random_cell]/BOARD_SIZE;
        row = empty[random_cell] % BOARD_SIZE;

ACuriousMind

@EmilioPisanty Wow, Prof. Et al.'s Erdös number is 1! :P

dmckee

You'll find it easier to prove to yourself without having to worry about the empty cells. Just write out the probability to select the nth item in a list of m using this method.

@John's code above is also O(n) in time as well, but is O(n) in space as well. However, it is clearer than the scheme I suggested and therefore easier to debug and maintain.

Bernardo Meurer

@dmckee Pretty interesting

John Rennie

I have to say David's idea is pretty slick :-)

Bernardo Meurer

@JohnRennie Nice solution too

I fixed the bug that crashed the program, and I have timer and score working

dmckee

5:11 PM

@JohnRennie Like most of my best ideas I stole it.

John Rennie

Great programmers steal!

3

dmckee

In fact, I think I first encountered it in a Stack Overflow post somewhere.

Bernardo Meurer

I will have to pause development for the weekend because I have VHDL stuff to do

sigh

Yashas Samaga

ibtimes.co.uk/…

o0

Bernardo Meurer

@dmckee My VHDL cpu works now :)

RISC, and the pipeline works already

dmckee

5:13 PM

@JohnRennie Indeed they do. NIH is the bane of getting stuff done.

Bernardo Meurer

Okay, gotta go buy food, be back in a bit folks

DanielSank

5:29 PM

@BernardoMeurer Get me food.

@JohnRennie C is terrible.

Header files. Blerg.

type-first declarations. Blerg.

user228700

@JohnR: I'm sorry that I've taken so long; I was a bit of a mess to respond properly but you have (what's probably an irritatingly small) mail :-)

DanielSank

Hi @EmilioPisanty.

Thanks for getting that driven oscillator problem.

Naveen Balaji

Hey guys! I need some suggestions for a good book on QFT; the one which starts QFT from scratch, builds up concepts intuitively and with the right mathematical rigor

0celouvsky

What math do you know?

DanielSank

@NaveenBalaji The "right" mathematical rigor depends entirely on what you already know, etc.

Slereah

5:39 PM

Basically no QFT book has mathematical rigor

Naveen Balaji

My math level is that of a 1st year graduate

DanielSank

@NaveenBalaji That means very little, actually.

Slereah