I am building a simple NN for a regression analysis (0.5 mln rows of data) in Keras. # Define model model = Sequential() model.add(Dense(32, activation = 'relu')) model.add(Dense(32, activation = 'sigmoid')) model.add(Dense(1)) # Define model parameters model.compile(optimizer = 'sgd', loss = 'mse', metrics = [tf.keras.metrics.MeanAbsoluteError()])  I am satisfied with results, but would like to know if there is any rule of thumb or recommendations how to build such models for a regression analysis. For example:  How many layers? Which activation functions? Which optimizer?  What is your state of the art approach, when you start to do such type of analysis? Especially appreciate any academic sources.
Is there a standard and accepted method for selecting the number of layers, and the number of nodes in each layer, in a feed-forward neural network? I'm interested in automated ways of building neural networks.
Destructive interference and energy conservation In case of interference, we know, energy is neither destroyed, nor created; but only redistributed. But in the case of an extremely thin film, due to a reflection and hence a phase difference of $\pi$, the film always appears dark due to destructive interference. So, where does the energy go? How can I access google.com outside the US? I live in the UK, and whenever I visit google.com I am redirected to google.co.uk, but I want to see my website's rankings on the US version (I presume the results are different). Is there a way to do this? Our team is developing a new system and it has a Warehouse table that must have a hierarchical relationship between entries since a customer can have 1st, 2nd, 3rd and Nth degree warehouses.  We first thought that  was the best way to do it. By creating a Parent and a Child column on the table and then making Parent the FK to Child (on the same table) but friend DBA told us that there is a different way.  So, for instance, we had thought about making a table like this:  CREATE TABLE Warehouse( filterId INT PRIMARY KEY IDENTITY, parentId INT NOT NULL, active BOOL DEFAULT 1, warehouseName VARCHAR(30) NOT NULL, FOREIGN KEY parentId REFERENCES Warehouse(filterId)  | FILTERID   | PARENTID | ACTIVE | WAREHOUSENAME | -------------------------------------------------- |          1 |        0 |      1 | N WAREHOUSE 1 | |          2 |        1 |      1 | ROOM 1        | |          3 |        1 |      1 | ROOM 2        | |          4 |        1 |      1 | ROOM 3        | |          5 |        1 |      1 | ROOM 4        | |          6 |        2 |      1 | SHELF 1       | |          7 |        2 |      1 | SHELF 2       | |          8 |        2 |      1 | SHELF 3       | |          9 |        2 |      1 | SHELF 4       | |         10 |        2 |      1 | SHELF 5       | |         11 |        2 |      1 | SHELF 6       | |         12 |        2 |      0 | SHELF 7       | |         13 |        3 |      1 | BOX 1         | |         14 |        3 |      0 | BOX 2         | |         15 |        3 |      1 | BOX 3         | |         16 |        3 |      1 | BOX 4         | --------------------------------------------------   But this DBA said that we should work on something like this:  CREATE TABLE Warehouse( filterId VARCHAR(20) PRIMARY KEY, active BOOLEAN DEFAULT 1, warehouseName VARCHAR(30) NOT NULL)   | FILTERID   | ACTIVE | WAREHOUSENAME | --------------------------------------- | 1.00       |      1 | N WAREHOUSE 1 | | 1.01       |      1 | ROOM 1        | | 1.02       |      1 | ROOM 2        | | 1.03       |      1 | ROOM 3        | | 1.04       |      1 | ROOM 4        | | 1.01.01    |      1 | SHELF 1       | | 1.01.02    |      1 | SHELF 2       | | 1.01.03    |      1 | SHELF 3       | | 1.01.04    |      1 | SHELF 4       | | 1.01.05    |      1 | SHELF 5       | | 1.01.06    |      1 | SHELF 6       | | 1.01.07    |      0 | SHELF 7       | | 1.01.01.01 |      1 | BOX 1         | | 1.01.01.02 |      0 | BOX 2         | | 1.01.01.03 |      1 | BOX 3         | | 1.01.01.04 |      1 | BOX 4         | ---------------------------------------   Which way should we follow?   On one hand we have a relationship between parentId and filterId; on the other we do not have any relationship, but it is easy to understand where does the entry belong.  Not all the warehouses are of the same level - that's what I mean by degree. They should be ordered like: For Customer A, 1 is parent of 1.1 and 1.2, 2 is parent of 2.1, 3 is parent of 3.1 and 4 is parent of 4.1 and 4.2 - but 1, 2, 3 and 4 are of the same level (1st level), and 1.1, 1.2, 2.1, 3.1, 4.1 and 4.2 are also of the same level (2nd level) but not of the same parents. Showing that $\gamma = -\int_0^{\infty} e^{-t} \log t \,dt$, where $\gamma$ is the Euler-Mascheroni constant. I'm trying to show that  $$\lim_{n \to \infty} \left[\sum_{k=1}^{n} \frac{1}{k} - \log n\right] = -\int_0^{\infty} e^{-t} \log t \,dt.$$  In other words, I'm trying to show that the above definitions of the Euler-Mascheroni constant $\gamma$ are equivalent.  In another post here (which I can't seem to find now) someone noted that  $$\int_0^{\infty} e^{-t} \log t \,dt = \left.\frac{d}{dx} \int_0^{\infty} t^x e^{-t} \,dt \right|_{x=0} = \Gamma&#39;(1) = \psi(1),$$  where $\psi$ is the digamma function.  This may be a good place to start on the right-hand side.  For the left-hand side I was tempted to represent the terms with integrals.  It is not hard to show that  $$\sum_{k=1}^{n} \frac{1}{k} = \int_0^1 \frac{1-x^n}{1-x} \,dx,$$  but I'm not sure this gets us anywhere.  Any help would be greatly appreciated. i Need a batch file to create a folder "test" in every removable device than i plug in my computer (pendrives and etc)  i am trying something like this  set "extDrive=" for /f %%D in ('wmic volume get driveLetter^ where drivertype=2 ) do set extDrive=%%D mkdir "%extDrive%\test"   Someone can tell me why this is not working ?? Trying to format USB (using Linux/fdisk) so it shows up on my Mac I have a USB drive that I can see/access/modify/etc in Linux/Ubuntu but it doesn't show up on my Mac OSX.  I did sudo fdisk /dev/sdb (where my USB is) and then g to create a new GPT partition table, n to make a new partition, used all default settings, then w to save and exit.  Then I did sudo mkfs.fat -F32 /dev/sdb1 to format the partition with a FAT32 filesystem.  I ejected the USB and put it in my Mac and it doesn't show up / get detected.  What did I miss? I have thus far avoided the nightmare that is testing multi-threaded code since it just seems like too much of a minefield.  I'd like to ask how people have gone about testing code that relies on threads for successful execution, or just how people have gone about testing those kinds of issues that only show up when two threads interact in a given manner?  This seems like a really key problem for programmers today, it would be useful to pool our knowledge on this one imho. I was laying on my bed, reading a book when the sun shone through the windows on my left. I happened to look at the wall on my right and noticed this very strange effect. The shadow of my elbow, when near the pages of the book, joined up with the shadow of the book even though I wasn't physically touching it.   I have posted :The video seems to be the wrong way up, but you still get the idea of what is happening.  What is causing this? Some sort of optical illusion where the light gets bent?  Coincidentally, I have been wondering about a similar effect recently where if you focus your eye on a nearby object, say, your finger, objects behind it in the distance seem to get curved/distorted around the edge of your finger. It seems awfully related...  EDIT: I could see the bulge with my bare eyes to the same extent as in the video! The room was well light and the wall was indeed quite bright. Admin privileges requiring for installing a package build though Packages Using osx 10.9 and packages for making package installer.  While installing a package made using Packages in /Applications location on a osx 10.9 machine, installer is asking for Admin password. Even though I had unchecked 'Require admin password for installation' while package making.  So, how to avoid this i.e a non-admin user should install this package. Package should install in /Applications location, so that non-admin user can use the app.  I check  and Modifying cat command to number paragraphs and display last paragraph only I have a text file for which I need to do three things:   Modify the "cat" command to highlight keywords whilst showing the complete contents of the file.  Modify the "cat" command to automatically number the paragraphs. These are separated by a single blank line.  Modify the "cat" command to display the final paragraph only.    The tricky part is that all of these need to be done by modifying the cat command.   I've seen many forum posts explaining that cat is not meant for this - and I can entirely see why. However, the challenge is that I have to use cat! What does ` (backquote/backtick) mean in commands? Does the potential energy of a single object exist? I know that potential energy exists for a system of objects. But why? Is there no potential energy for a single object system? I assume that there is.  Consider the earth-object system. Suppose an external force lifts the object above the earth. Then the work done by it gets stored in the earth-object system as potential energy.Right?  Now, my question is that is the potential energy always zero for a single object system.   MY REASONING  If we consider the object only as the system and lift it above the Earth, we are doing positive work on it and filling it with energy and the gravitational field of the Earth is doing negative work on it and draining it of energy. Thus whenever the object is moving it has kinetic energy which is fine. But when it is not moving,i.e. when its weight is equal to the force applied by us, the net work done is zero and so the object should not have any kinetic energy. Does it have potential energy? Constructing $g$ holomorphic differentials on $\omega^3=(z-1) \cdots (z-8)$ Let us have a surface $X$ which satisfy the equation $\omega^3 = (z-1)(z-2)\cdots (z-8)$ It's stated in the task, that there are exactly $g$ holomorphic differentials on the curve. How can I find $g$ and construct them?  The genus $g$ of this curve (I tried to use Riemann-Hurwitz theorem)  The map $X(z,\omega) \to CP^1(\omega)$ has degree 3. and we have 8 branching points with 3 leaves at each. $\chi(Domain) = DegreeOfMap * \chi(Target) - \sum_{points}(BranchingLeaves - 1) $ $2-2g = 3 *(2) - 8*2 $ hence $ 12 = 2g$ and  $g = 6$ I know that in case of hyperelliptic curve there are $g-2$ (If i'm not mistaken) holomorphic differetials and they are of sort $\frac{z^k dz}{w}$. But the form of the curve equation was heavily used. UPD: there is a branhing point at $\infty$, because if we go around all points $ 1 \cdots 8$ at once, we get that cubic root of the right side is multiplied by $\exp{4 \pi /3}$ $2-2g = 3 *(2) - 9*2 $ hence $ 12 = 2g$ and  $g = 7$ (I hope that this is true) I am studying General Relativity and some basic QFTs. It bothers me a lot that different books use different metric signatures, i.e. $(-+++)$ and $(+---).$ Can anyone tell me the advantages of using both of them, or why some people prefer the former while some prefer the latter? I would like to know which one should I while tackling different problems. I have a live USB made with the standard Ubuntu disk image creator for 16.04 LTS. In the current state, I can boot to this disk, but it still requires the original USB to run properly at all times.  Attempting to pull the drive and use the system generates a large amount of I/O errors, further suggesting that the USB drive is actually needed for things not already loaded into RAM (For example, Firefox worked without the USB, but I used it once before already. apt, on the other hand, did not.)  Is there a way to copy the entire Ubuntu live disk to RAM, so I can remove the drive and free up a USB slot for other things? Cardinality of a set A is strictly less than the cardinality of the power set of A typeof is an operator and a function I know when evaluated it gives one but I can't figure out how to prove it.  Can anyone help? I believe it requires L'Hopitals rule and taking a natural log but i cannot figure out the exact math. How to correct for small p-value due to very large sample size I am running into a problem where an independent variable, which should have no predictive power on the dependent variable based on domain knowledge, comes out with very small p-value because the sample size is very large(~100,000). If I only use &lt; 5000 data points, then the p-value becomes large enough to support the prior that the variable is insignificant. However, I don't think tweaking the sample size to get to the desired conclusion is a good practice. Is there any procedure to adjust for small p-value simply due to huge sample size? Do SSD's really last 285 years? Some Sold State Disks (SSD) have a  (MTBF) of 2,500,000 hours. If you divide that by the rough number of hours in a year you get 2500000÷(365×24) ~= 285 years before there is a problem.  I know that the first generation SSD's used to have a short life - but now the estimated time before they fail seems absurdly high. Most warranties only cover them for 1-3 years it seems.  How long are the modern, SATA III drives supposed to last?