alxv
Joined 19 years ago
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Recent submissions
Comment · 8 years ago
Comment · 9 years ago
You only need 2 processors, since each cores gives you 2 vCPUs. "For the n1 series of machine types, a virtual CPU is implemented as a single hardware hyper-thread" --https://cloud.google.com/compute/docs/machine-types
Comment · 9 years ago
You are missing a crucial piece here to have consistent hashing: you also need hash the names of the servers. With consistent hashing you hash both the names of the requests and of the servers, then you assign the request to the server with closest hash (under the modulus). With this scheme, you only need to remap 1/n of the keys (where n is the number of servers).
Comment · 9 years ago
There is a proof shown in this handout: https://people.eecs.berkeley.edu/~sinclair/cs271/n15.pdf
It's hard to understand why this technique works so well without digging deep in the math. Roughly speaking, if you throw n balls in n bins at random, the maximum of number balls in any bins will grow surprisingly quickly (because of the birthday paradox). However, if we allow ourselves to choose between two random bins instead of one, and put the ball in the one with the fewest balls in it, the maximum number of balls in any bins grow much more slowly (i.e., O(ln ln n)). Hence, having that one extra random choice allows us to get surprisingly close to the optimal approach of comparing all bins (which would give us O(1)), without doing all that work.
Comment · 9 years ago
The method is called "Power of Two Random Choices" (http://www.eecs.harvard.edu/~michaelm/postscripts/handbook20...). And the two-choices paradigm is widely applicable beyond load balancing. In particular, it applies to hash table design (e.g. cuckoo hashing) and cache eviction schemes (https://danluu.com/2choices-eviction/).
Comment · 9 years ago
What happens when the number of servers changes? The cache hit rate would likely drop to zero until it warms up again, which is a good way to accidentally overload your systems.
Load balancing based on consistent hashing is the better way to implement this.
Comment · 9 years ago
If your employer 401k plan allows it, you can roll over after-tax 401k contributions to a Roth IRA (a.k.a. mega-backdoor Roth IRA).
Comment · 10 years ago
Sorry, it turns that was misunderstanding from my part. It turns out we cannot solve a board row by row without revisiting the previous rows. The board below is a counterexample:
101
010
100
solution #1:
110
100
000
solution #2:
110
110
000
The move matrix M for all boards of size 3n + 2 appears to be singular. This means these boards may have no solution or a large number of solutions.
Comment · 10 years ago
For every boards are two chessboard patterns we can solve for. For example, for a 3x3 board we can have:
101 010
010 or 101
101 010
We can represent any N×N board as a N² vector. So, we can represent one of the chessboard pattern as:
010
101 = 010101010 = y
010
110
111 = 110111010 = y0
010
(y - y0) = Mx
1 + 1 = 0 (mod 2)
0 + 1 = 1 (mod 2)
110110000
110110000
111111000
011011000
110110110
111111111 = M
011011011
000110110
000111111
000011011
(y - y0) = Mx
(010101010 - 110111010) = Mx
100010000 = Mx
111100100 = x (by Gaussian elimination)
111
100
100
Comment · 10 years ago
Like Lights Out, this game can be solved using Gaussian elimination over Z/2 (integers modulo 2). This means the order of the tiles you press do not matter, and that you can solve the board by forming the desired pattern row by row.
Comment · 10 years ago
During the winter, most fresh vegetables in Canada are imported from Mexico and the US. These are mostly breed for shelf life and usually bland. In the summer, local fruit and vegetable can be quite tasty if you know where to shop. The public markets of Montreal are very good (http://www.marchespublics-mtl.com/). You can also subscribe to get weekly organic baskets from local farms during the harvest season (http://www.paniersbio.org/en/).
Comment · 10 years ago
On the other hand, the bland stuff doesn't poison you as much with lead.
http://www.environmentalhealthnews.org/ehs/news/lead-in-vine...
Comment · 10 years ago
In the U.S., Californian olive oils are your best bet. Otherwise, Costco Kirkland Signature olive oil (which is now Greek oil [1]) is another good choice.
Outside of Italy, it's difficult to find Italian olive oils that are not blended. The 2014 and 2015 harvest seasons have been terrible due a bacterial blight [2] that crippled many olive farms in Southern Italy.
[1] http://www.seattletimes.com/business/retail/costco-embraces-...
It's large enough for the double-Gauss lens (a.k.a. normal prime lens) to have a nice shallow deep of field wide open. f/1.2 is close to the limit of a typical SLR mount. So a normal 50mm f/1.2 lens gets us 42mm of aperture. This means we can get the same depth of field and angle of view as a 6x7 medium format with a 110mm f/2.8 lens or a 4x5 large format with a 180mm f/4.5 (but with a much smaller system!) And we get a faster lens as a bonus.
Smaller formats lose some of that versatility of composition. The focal length of the normal lens on APS-C is 32mm. We would need f/0.8 lens to the same DOF. That's not possible on an SLR mount. Mirrorless systems with their shorter flange distances could get us there. But even then there are limits to how short the flange can be because image sensors become much less efficient as the angle of incidence of the light hitting them increases.