UPDATE
------

Since 2019.2 version you can enable it in the Project view options, toggle the **Show Visibility Icons**:


[![Show Visibility Icons][1]][1]

----------


For older versions:

This option was disabled intentionally, see [this comment](https://youtrack.jetbrains.com/issue/IDEA-172513#comment=27-2150075) for the explanation:

&gt; This information was intentionally removed, as we believe that it
&gt; brings more clutter than actual value.

To enable it back add `-Dide.projectView.show.visibility=true` in `Help` | `Edit Custom VM Options`.


  [1]: https://i.stack.imgur.com/PG5yx.png

Since 2019.2 there is actually an easy to use option as described in [comment](https://youtrack.jetbrains.com/issue/IDEA-172513#focus=streamItem-27-3597991.0-0):

&gt; you can find this setting in options menu of Project Tool Window. It&#39;s called &quot;Show Visibility Icons&quot;

*I indicate matrices by capital letters, and vectors by small letters.*

I need to solve the following system of linear inequalities for vector `v`: 

&lt;!-- language: lang-none --&gt;

    min(rv - (u + Av), v - s) = 0

where `0` is a vector of zeros.

where `r` is a scalar, `u` and `s` are vectors, and `A` is a matrix.

Defining `z = v-s`, `B=rI - A`, `q=-u + Bs`, I can rewrite the previous problem as a [linear complementarity problem][1] and hope to use an LCP solver, for example from `openopt`:

&lt;!-- language: lang-none --&gt;

    LCP(M, z): min(Bz+q, z) = 0

or, in matrix notation:
    
&lt;!-- language: lang-none --&gt;

    z&#39;(Bz+q) = 0
    z &gt;= 0
    Bz + q &gt;= 0

---
The problem is that my system of equations is huge. To create `A`, I 

- Create four matrices `A11`, `A12`, `A21`, `A22` using `scipy.sparse.diags`
- And stack them together as `A = scipy.sparse.bmat([[A11, A12], [A21, A22]])`
- (This also means that `A` is not symmetric, and hence some efficient translations into `QP` problems won&#39;t work)

`openopt.LCP` apparently cannot deal with sparse matrices: When I ran this, my computer crashed. Generally, `A.todense()` will lead to a memory error. Similarly, `compecon-python` is not able to solve `LCP` problems with sparse matrices. 

What alternative `LCP` implementations are fit for this problem?


---

I really did not think *sample data* was required for a general &quot;which tools to solve LCP&quot; question were required, but anyways, here we go

    from numpy.random import rand
    from scipy import sparse
    
    n = 3000
    r = 0.03
    
    A = sparse.diags([-rand(n)], [0])
    s = rand(n,).reshape((-1, 1))
    u = rand(n,).reshape((-1, 1))
    
    B = sparse.eye(n)*r - A
    q = -u + B.dot(s)
    
    q.shape
    Out[37]: (3000, 1)
    B
    Out[38]: 
    &lt;3000x3000 sparse matrix of type &#39;&lt;class &#39;numpy.float64&#39;&gt;&#39;
    	with 3000 stored elements in Compressed Sparse Row format&gt;




--- 

Some more pointers:

 - `openopt.LCP` crashes with my matrices, I assume it converts the matrices to dense before continuing
 - `compecon-python` outright fails with some error, it apparently requires dense matrices and has no fallback for sparsity
 - `B` is not positive semi-definite, so I cannot rephrase the linear complementarity problem (LCP) as a convex quadratic problem (QP)
 - All QP sparse solvers from [this exposition][2] require the problem to be convex, which mine is not
 - In Julia, [PATHSolver][3] can solve my problem (given a license). However, there are problems calling it from Python with [PyJulia][3] ([my issue report here][4])
 - Also Matlab has an LCP solver that apparently can handle sparse matrices, but there implementation is even more wacky (and I really do not want to fallback on Matlab for this)


  [1]: https://en.wikipedia.org/wiki/Linear_complementarity_problem
  [2]: https://github.com/stephane-caron/qpsolvers
  [3]: https://github.com/JuliaPy/pyjulia
  [4]: https://github.com/JuliaPy/pyjulia/issues/123

LCP with sparse matrix

I am trying to create a chat app using reactJS and pusher, i am getting this error-

&gt; Could not proxy request /pusher/auth from localhost:3000 to
&gt; http://localhost:5000 (ECONNREFUSED)

in package.json file i have set proxy as-

    &quot;proxy&quot;: &quot;http://localhost:5000&quot;

and my `localhost` is defined as `127.0.0.1` in `/etc/hosts` file.  
I have also checked for the port availability using `netstat`, but these all seems to be correct. Can anybody help? 

Could not proxy request /pusher/auth from localhost:3000 to http://localhost:5000 (ECONNREFUSED)

I&#39;ve recently upgraded to Intellij IDEA 2017.2 and access modifier icons disappeared from my file tree... How to get them back?

[![][1]][1]


  [1]: https://i.stack.imgur.com/gr70C.png

How to show access modifiers for classes in IntelliJ IDEA?

<p>I've recently upgraded to Intellij IDEA 2017.2 and access modifier icons disappeared from my file tree... How to get them back?</p>
<p><a href="https://i.stack.imgur.com/gr70C.png" target="_blank" rel="noopener noreferrer"><img src="https://i.stack.imgur.com/gr70C.png" alt=""></a></p>


There is a way in webstorm to comment or uncomment a specific line or selected block of source code with shortcut?
I try to use &lt;kbd&gt;CTRL&lt;/kbd&gt; + &lt;kbd&gt;/&lt;/kbd&gt; but doesn&#39;t work for me

IntelliJ shortcut to comment line

I&#39;m trying to add google play services to my libGDX project in IntelliJ Idea. I&#39;ve followed the setup guide here: https://developers.google.com/android/guides/setup

which looks pretty straightforward. I just added those lines to my build.gradle in the corresponding section, so things look now like:

    project(&quot;:android&quot;) {
        apply plugin: &quot;android&quot;
        apply plugin: &#39;com.android.application&#39;
        
        configurations { natives }
        
        dependencies {
            compile project(&quot;:core&quot;)
            compile &quot;com.badlogicgames.gdx:gdx-backend-android:$gdxVersion&quot;
            natives &quot;com.badlogicgames.gdx:gdx-platform:$gdxVersion:natives-armeabi&quot;
            natives &quot;com.badlogicgames.gdx:gdx-platform:$gdxVersion:natives-armeabi-v7a&quot;
            natives &quot;com.badlogicgames.gdx:gdx-platform:$gdxVersion:natives-arm64-v8a&quot;
            natives &quot;com.badlogicgames.gdx:gdx-platform:$gdxVersion:natives-x86&quot;
            natives &quot;com.badlogicgames.gdx:gdx-platform:$gdxVersion:natives-x86_64&quot;
            compile &quot;com.badlogicgames.gdx:gdx-box2d-platform:$gdxVersion&quot;
            natives &quot;com.badlogicgames.gdx:gdx-box2d-platform:$gdxVersion:natives-armeabi&quot;
            natives &quot;com.badlogicgames.gdx:gdx-box2d-platform:$gdxVersion:natives-armeabi-v7a&quot;
            natives &quot;com.badlogicgames.gdx:gdx-box2d-platform:$gdxVersion:natives-x86&quot;
            compile &quot;com.badlogicgames.gdx:gdx-freetype:$gdxVersion&quot;
            natives &quot;com.badlogicgames.gdx:gdx-freetype-platform:$gdxVersion:natives-armeabi&quot;
            natives &quot;com.badlogicgames.gdx:gdx-freetype-platform:$gdxVersion:natives-armeabi-v7a&quot;
            natives &quot;com.badlogicgames.gdx:gdx-freetype-platform:$gdxVersion:natives-arm64-v8a&quot;
            natives &quot;com.badlogicgames.gdx:gdx-freetype-platform:$gdxVersion:natives-x86&quot;
            natives &quot;com.badlogicgames.gdx:gdx-freetype-platform:$gdxVersion:natives-x86_64&quot;
            compile &#39;com.google.android.gms:play-services:11.2.0&#39;
        }
    }

Then I try to sync my gradle project in Idea just to get that &quot;Failed to resolve&quot; error.

Well, the setup guide also says &quot;Be sure you update this version number each time Google Play services is updated&quot;, but the problem is that it seems nearly impossible to find that version number: my Google Play Services SDK version according to the Android SDK manager is &quot;43&quot;, and so far I have been unable to correlate such &quot;11.2.0&quot; or whatever typical version string with the &quot;43&quot; version number. Not that the setup guide says nothing about that.

Anyway, I have tried a lot of things from the plethora of questions related to this to no avail. Specifically, I have to point out that I do have my Android SDK properly updated and I&#39;m sure it is the one it&#39;s being used by Idea (I&#39;ve already triple-checked this...):

[![Android SDK Manager][1]][1]
[![Project Structure][2]][2]

I&#39;m using the API level 26, but anyway the other defines do use the very same directory for the Android SDK. Moreover, I do NOT have any other android SDK installed at all in this laptop, so there&#39;s no question about Idea being using that one and that one only. 

Any ideas are more than welcome.

Thanks in advance!


  [1]: https://i.stack.imgur.com/gIYz7.png
  [2]: https://i.stack.imgur.com/bSxSl.png

Failed to resolve: com.google.android.gms:play-services in IntelliJ Idea with gradle

I am running IntelliJ IDEA 2017.2.3. I installed Groovy 2.4.12 via Homebrew (OS X). When I open a Groovy source file (or a `Jenkinsfile`), I get the following:

&gt;Groovy SDK is not configured for module &#39;my-module&#39; . . . . . *Configure Groovy SDK...*

Clicking &quot;Configure Groovy SDK...&quot; leads me to the following dialog:

[![Error: library is not specified][1]][1]

I tried hitting &quot;Create...&quot; and selecting many different Groovy-related folders and executables, but nothing works.

How can I get IntelliJ IDEA to accept my Groovy SDK?

  [1]: https://i.stack.imgur.com/iNskM.png

Configuring Groovy SDK within IntelliJ IDEA

I&#39;m trying to run my JSQL parser class, but I&#39;m getting `Error: java: invalid source release 1.9`. 

I tried to following [this answer][1]. I changed File&gt; Build,Execution,Deployment&gt; Java Compiler&gt; Project bytecode version: 1.8.  However, I can&#39;t change the Module language level and Project language level to 1.8 because there&#39;s not option for that. I still get the same error below.

**Error**
[![enter image description here][2]][2]

**Code**

    package cs4321.project2;

    import java.io.FileReader;
    import net.sf.jsqlparser.parser.CCJSqlParser;
    import net.sf.jsqlparser.statement.Statement;
    import net.sf.jsqlparser.statement.select.Select;
    
    public class Parser {
        private static final String queriesFile = &quot;resources/input/queries.sql&quot;;
    
        public static void main(String[] args) {
            try {
                CCJSqlParser parser = new CCJSqlParser(new FileReader(queriesFile));
                Statement statement;
                while ((statement = parser.Statement()) != null) {
                    System.out.println(&quot;Read statement: &quot; + statement);
                    Select select = (Select) statement;
                    System.out.println(&quot;Select body is &quot; + select.getSelectBody());
                }
            } catch (Exception e) {
                System.err.println(&quot;Exception occurred during parsing&quot;);
                e.printStackTrace();
            }
        }
    }


  [1]: https://stackoverflow.com/a/42650624/7327018
  [2]: https://i.stack.imgur.com/XlBuf.png

intellij idea - Error: java: invalid source release 1.9

I have installed Material Theme UI and it made my IDE blackish. Later I decided to remove and and removed plugin. Unfortunately, this didn&#39;t give default colors back, some parts of IDE, for example Project pane, remained blackish.

How ro recover?

How to remove material theme from IntelliJ / PyCharm?

How to remove material theme (or reset to defaults) from IntelliJ / PyCharm?

[C# 7.2 introduces the private protected modifier][1]. 

I&#39;ve always protected access to fields with properties, allowing access via the Get/Set methods as I typically don&#39;t want the internal state of my object modified by anything other than my own class.

I&#39;m trying to understand why the C# language team have added this feature. After an extensive search on google, and reading and watching the &#39;what&#39;s new&#39; media (I&#39;ve watched the [press release][2], [details][3] and [video by Mads Torgerson][4]), I am still none the wiser.

To me, this appears to allow a developer to break the Liskov Substitution principle, but this may be because I do not understand why this feature now exists.

I understand how it can be used, just not why - please can someone provide a real-world usage example rather than the contrived one in the MSDN documents?

  [1]: https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/private-protected
  [2]: https://blogs.msdn.microsoft.com/dotnet/2017/11/15/welcome-to-c-7-2-and-span/?utm_source=vs_developer_news&amp;utm_medium=referral
  [3]: https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-7-2
  [4]: https://channel9.msdn.com/events/Connect/2017/T122

Content Type	Original Author	Original Content on Stackoverflow
Question	mdziob	View Question on Stackoverflow
Solution 1 - Intellij Idea	CrazyCoder	View Answer on Stackoverflow
Solution 2 - Intellij Idea	Chris Suszyński	View Answer on Stackoverflow

How to show access modifiers for classes in IntelliJ IDEA?

Intellij Idea Problem Overview

Intellij Idea Solutions

Solution 1 - Intellij Idea

UPDATE

Solution 2 - Intellij Idea

Could not proxy request /pusher/auth from localhost:3000 to http://localhost:5000 (ECONNREFUSED)

LCP with sparse matrix

Attributions