It&#39;s not oficial, but *Serhiy Topchiy* did a benchmark with different instance types:

http://epamcloud.blogspot.com.br/2013/03/testing-amazon-ec2-network-speed.html

For US-EAST-1, it seems that LOW corresponds to 50Mb/s, Moderate corresponds to 300Mb/s and High corresponds to 1Gb/s.

My recent experience here: https://serverfault.com/questions/1094608/benchmarking-aws-outbound-internet-bandwidth-egress-up-to-25-gbps

We ran a live video broadcast on two AWS EC2 servers, hosting 500 viewers, that degraded catastrophically after 10 minutes.

We reproduced the outbound bandwidth throttling with iperf (see link above).

I believe it was mentioned at the reInvent 2013 conference that the different properties are related to the underlying network connection:  Some servers have 10GB connections (High) some have 1GB (Moderate) and some have 100MB (Low).

I cannot find any on-line documentation to confirm this, however.

Edit:  There is an interesting article on Packet per second limit [available here][1]

Since this question was first posed, AWS has released more information on the networking stack, and many of the newer instance families can support up to 25Gbps with the appropriate ENA drivers.  It looks like much of the increased performance is due to the new Nitro system.


  [1]: https://www.bluematador.com/blog/ec2-packets-per-second-guaranteed-throughput-vs-best-effort

I&#39;m trying to use Kotlin in my Android project. I need to create custom view class. Each custom view has two important constructors:

    public class MyView extends View {
        public MyView(Context context) {
            super(context);
        }
    
        public MyView(Context context, AttributeSet attrs) {
            super(context, attrs);
        }
    }

`MyView(Context)` is used to instantiate view in code, and `MyView(Context, AttributeSet)` is called by layout inflater when inflating layout from XML.

Answer to [this question][1] suggests that I use constructor with default values or factory method. But here&#39;s what we have:

**Factory method:**

    fun MyView(c: Context) = MyView(c, attrs) //attrs is nowhere to get
    class MyView(c: Context, attrs: AttributeSet) : View(c, attrs) { ... }

or  

    fun MyView(c: Context, attrs: AttributeSet) = MyView(c) //no way to pass attrs.
                                                            //layout inflater can&#39;t use 
                                                            //factory methods
    class MyView(c: Context) : View(c) { ... }

**Constructor with default values:**

    class MyView(c: Context, attrs: AttributeSet? = null) : View(c, attrs) { ... }
    //here compiler complains that 
    //&quot;None of the following functions can be called with the arguments supplied.&quot;
    //because I specify AttributeSet as nullable, which it can&#39;t be.
    //Anyway, View(Context,null) is not equivalent to View(Context,AttributeSet)

**How can this puzzle be resolved?**

----------

**UPDATE:** Seems like we can use `View(Context, null)` superclass constructor instead of `View(Context)`, so factory method approach seems to be the solution. But even then I can&#39;t get my code to work:

    fun MyView(c: Context) = MyView(c, null) //compilation error here, attrs can&#39;t be null
    class MyView(c: Context, attrs: AttributeSet) : View(c, attrs) { ... }

or 

    fun MyView(c: Context) = MyView(c, null) 
    class MyView(c: Context, attrs: AttributeSet?) : View(c, attrs) { ... }
    //compilation error: &quot;None of the following functions can be called with 
    //the arguments supplied.&quot; attrs in superclass constructor is non-null

  [1]: https://stackoverflow.com/questions/19299525/kotlin-secondary-constructor/19310740

How to create constructor of custom view with Kotlin

I&#39;m trying to remove leading and trailing space in 2nd column of the below `input.txt`:

`Name, Order&#160;&#160;`&lt;br&gt;
`Trim, working`&lt;br&gt;
`cat,cat1`

I have used the below `awk` to remove leading and trailing space in 2nd column but it is not working. What am I missing?

    awk -F, &#39;{$2=$2};1&#39; input.txt

This gives the output as:

`Name, Order&#160;&#160;`&lt;br&gt;
`Trim, working`&lt;br&gt;
`cat,cat1`

Leading and trailing spaces are not removed.

Trim leading and trailing spaces from a string in awk

When choosing an amazon aws instance type to launch, there is a property of each type which is &quot;Network Performance&quot; which is either &quot;Low&quot;, &quot;Moderate&quot;, or &quot;High&quot;.
I&#39;m wondering what this exactly means. Will my ping be lower if I choose low? Or will it be ok as long as many users aren&#39;t logged in at once?

I&#39;m launching a real time multiplayer game and I am so I am curious as to exactly what is meant under &quot;network performance&quot;. I actually need fairly low memory and processing power, but instances with those criteria usually have &quot;low&quot; network performance.

Has anyone experience with the different network performances or have more information?

Thanks!

What does amazon aws mean by &quot;network performance&quot;?

When choosing an amazon aws instance type to launch, there is a property of each type which is "Network Performance" which is either "Low", "Moderate", or "High".
I'm wondering what this exactly means. Will my ping be lower if I choose low? Or will it be ok as long as many users aren't logged in at once?
I'm launching a real time multiplayer game and I am so I am curious as to exactly what is meant under "network performance". I actually need fairly low memory and processing power, but instances with those criteria usually have "low" network performance.
Has anyone experience with the different network performances or have more information?
Thanks!

I have found an interesting performance regression in a small C++ snippet, when I enable C++11:

    #include &lt;vector&gt;

    struct Item
    {
      int a;
      int b;
    };

    int main()
    {
      const std::size_t num_items = 10000000;
      std::vector&lt;Item&gt; container;
      container.reserve(num_items);
      for (std::size_t i = 0; i &lt; num_items; ++i) {
        container.push_back(Item());
      }
      return 0;
    }

With g++ (GCC) 4.8.2 20131219 (prerelease) and C++03 I get:

    milian:/tmp$ g++ -O3 main.cpp &amp;&amp; perf stat -r 10 ./a.out

    Performance counter stats for &#39;./a.out&#39; (10 runs):

            35.206824 task-clock                #    0.988 CPUs utilized            ( +-  1.23% )
                    4 context-switches          #    0.116 K/sec                    ( +-  4.38% )
                    0 cpu-migrations            #    0.006 K/sec                    ( +- 66.67% )
                  849 page-faults               #    0.024 M/sec                    ( +-  6.02% )
           95,693,808 cycles                    #    2.718 GHz                      ( +-  1.14% ) [49.72%]
      &lt;not supported&gt; stalled-cycles-frontend 
      &lt;not supported&gt; stalled-cycles-backend  
           95,282,359 instructions              #    1.00  insns per cycle          ( +-  0.65% ) [75.27%]
           30,104,021 branches                  #  855.062 M/sec                    ( +-  0.87% ) [77.46%]
                6,038 branch-misses             #    0.02% of all branches          ( +- 25.73% ) [75.53%]

          0.035648729 seconds time elapsed                                          ( +-  1.22% )

With C++11 enabled on the other hand, the performance degrades significantly:

    milian:/tmp$ g++ -std=c++11 -O3 main.cpp &amp;&amp; perf stat -r 10 ./a.out
    
    Performance counter stats for &#39;./a.out&#39; (10 runs):

            86.485313 task-clock                #    0.994 CPUs utilized            ( +-  0.50% )
                    9 context-switches          #    0.104 K/sec                    ( +-  1.66% )
                    2 cpu-migrations            #    0.017 K/sec                    ( +- 26.76% )
                  798 page-faults               #    0.009 M/sec                    ( +-  8.54% )
          237,982,690 cycles                    #    2.752 GHz                      ( +-  0.41% ) [51.32%]
      &lt;not supported&gt; stalled-cycles-frontend 
      &lt;not supported&gt; stalled-cycles-backend  
          135,730,319 instructions              #    0.57  insns per cycle          ( +-  0.32% ) [75.77%]
           30,880,156 branches                  #  357.057 M/sec                    ( +-  0.25% ) [75.76%]
                4,188 branch-misses             #    0.01% of all branches          ( +-  7.59% ) [74.08%]

        0.087016724 seconds time elapsed                                          ( +-  0.50% )

Can someone explain this? So far my experience was that the STL gets faster by enabling C++11, esp. thanks to move semantics.

**EDIT:** As suggested, using `container.emplace_back();` instead the performance gets on par with the C++03 version. How can the C++03 version achieve the same for `push_back`?

    milian:/tmp$ g++ -std=c++11 -O3 main.cpp &amp;&amp; perf stat -r 10 ./a.out

    Performance counter stats for &#39;./a.out&#39; (10 runs):

            36.229348 task-clock                #    0.988 CPUs utilized            ( +-  0.81% )
                    4 context-switches          #    0.116 K/sec                    ( +-  3.17% )
                    1 cpu-migrations            #    0.017 K/sec                    ( +- 36.85% )
                  798 page-faults               #    0.022 M/sec                    ( +-  8.54% )
           94,488,818 cycles                    #    2.608 GHz                      ( +-  1.11% ) [50.44%]
      &lt;not supported&gt; stalled-cycles-frontend 
      &lt;not supported&gt; stalled-cycles-backend  
           94,851,411 instructions              #    1.00  insns per cycle          ( +-  0.98% ) [75.22%]
           30,468,562 branches                  #  840.991 M/sec                    ( +-  1.07% ) [76.71%]
                2,723 branch-misses             #    0.01% of all branches          ( +-  9.84% ) [74.81%]

       0.036678068 seconds time elapsed                                          ( +-  0.80% )

std::vector performance regression when enabling C++11

I tested the speed of `memcpy()` noticing the speed drops dramatically at i*4KB. The result is as follow: the Y-axis is the speed(MB/second) and the X-axis is the size of buffer for `memcpy()`, increasing from 1KB to 2MB. Subfigure 2 and Subfigure 3 detail the part of 1KB-150KB and 1KB-32KB.

Environment：

CPU : Intel(R) Xeon(R) CPU E5620  @ 2.40GHz 

OS :  2.6.35-22-generic #33-Ubuntu

GCC compiler flags : -O3 -msse4 -DINTEL_SSE4 -Wall -std=c99
 
![Graphs of memcpy speed showing troughs every 4k][1]

I guess it must be related to caches, but I can&#39;t find a reason from the following cache-unfriendly cases:

 * https://stackoverflow.com/questions/12264970/why-is-my-program-slow-when-looping-over-exactly-8192-elements

 * https://stackoverflow.com/questions/11413855/why-is-transposing-a-matrix-of-512x512-much-slower-than-transposing-a-matrix-of

Since the performance degradation of these two cases are caused by unfriendly loops which read scattered bytes into the cache, wasting the rest of the space of a cache line.

Here is my code:

    void memcpy_speed(unsigned long buf_size, unsigned long iters){
        struct timeval start,  end;
        unsigned char * pbuff_1;
        unsigned char * pbuff_2;

        pbuff_1 = malloc(buf_size);
        pbuff_2 = malloc(buf_size);

        gettimeofday(&amp;start, NULL);
        for(int i = 0; i &lt; iters; ++i){
            memcpy(pbuff_2, pbuff_1, buf_size);
        }   
        gettimeofday(&amp;end, NULL);
        printf(&quot;%5.3f\n&quot;, ((buf_size*iters)/(1.024*1.024))/((end.tv_sec - \
        start.tv_sec)*1000*1000+(end.tv_usec - start.tv_usec)));
        free(pbuff_1);
        free(pbuff_2);
    }

UPDATE
=====
Considering suggestions from @usr, @ChrisW and @Leeor, I redid the test more precisely and the graph below shows the results. The buffer size is from 26KB to 38KB, and I tested it every other 64B(26KB, 26KB+64B, 26KB+128B, ......, 38KB). Each test loops 100,000 times in about 0.15 second. The interesting thing is the drop not only occurs exactly in 4KB boundary, but also comes out in 4*i+2 KB, with a much less falling amplitude.


![More graphs showing performance drops][2]


PS
==
@Leeor offered a way to fill the drop, adding a 2KB dummy buffer between `pbuff_1` and `pbuff_2`. It works, but I am not sure about Leeor&#39;s explanation.


![enter image description here][3] 


  [1]: http://i.stack.imgur.com/TJ4Xx.png
  [2]: http://i.stack.imgur.com/qto0R.png
  [3]: http://i.stack.imgur.com/NL3uy.png

Why does the speed of memcpy() drop dramatically every 4KB?

I&#39;m thinking about the solution for my application. Here&#39;s the situation: I have a class with a method that takes ObjectA as an input parameter and calls several small methods. Each one of these methods needs some parts of the ObjectA (they don&#39;t overlap, i.e. `method1()` needs `ObjectA.field1` and `ObjectA.field2`, `method2()` needs `ObjectA.field3` and so on...) 

Given the general good code practices and performance, is it better to pass ObjectA to each one of these methods so they can extract the value they need on their own or is it better just pass them values? I mean:

    method1(ObjectA);
    method2(ObjectA);

or

    method1(Object1.getField1(), ObjectA.getField2());
    method2(ObjectA.getField3());


Passing whole object vs passing object&#39;s property

What&#39;s the difference between an [RDD&#39;s][1] `map` and `mapPartitions` method? And does `flatMap` behave like `map` or like `mapPartitions`? Thanks.

(edit)
i.e. what is the difference (either semantically or in terms of execution) between

      def map[A, B](rdd: RDD[A], fn: (A =&gt; B))
                   (implicit a: Manifest[A], b: Manifest[B]): RDD[B] = {
        rdd.mapPartitions({ iter: Iterator[A] =&gt; for (i &lt;- iter) yield fn(i) },
          preservesPartitioning = true)
      }

And:

      def map[A, B](rdd: RDD[A], fn: (A =&gt; B))
                   (implicit a: Manifest[A], b: Manifest[B]): RDD[B] = {
        rdd.map(fn)
      }

  [1]: https://spark.apache.org/docs/latest/api/scala/#org.apache.spark.rdd.RDD

Apache Spark: map vs mapPartitions?

I realize that a similarly-worded question has been asked before, but this is different. I am pretty new at developing android apps and I have three questions regarding the difference(s) between the `android:onclick=&quot;&quot;` XML attribute and the `setOnClickListener` method.

1. What are the differences between the two? Is the difference between the two implementations found at compile time or run time or both?

2. What use cases are favorable to which implementation?

3. What difference(s) does the use of fragments in Android make in implementation choice?

Android onClick in XML vs. OnClickListener

I have the following code that checks if an internet connection is present.

    import urllib2
    
    def internet_on():
        try:
            response=urllib2.urlopen(&#39;http://74.125.228.100&#39;,timeout=20)
            return True
        except urllib2.URLError as err: pass
        return False

This will test for an internet connection, but how effective is it?

I know internet varies in quality from person to person, so I&#39;m looking for something that is most effective for the broad spectrum, and the above code seems like there might be loopholes where people could find bugs. For instance if someone just had a really slow connection, and took longer than 20 seconds to respond.

Test if an internet connection is present in python

I&#39;m working on Open Network Video Interface Forum-Java project and following the steps described in the [ONVIF Application Programmer&#39;s Guide][1].

I have generated sources from the `wsdls` provided in ONVIF site. I&#39;m able to retrieve the live stream URI using the `media.wsdl`. Now I have an issue with recording. The codes that I have tried is given below:

    RecordingService recording_ervice = new RecordingService();
    RecordingPort record_port = recording_ervice.getRecordingPort();


    BindingProvider bindingProvider = (BindingProvider) record_port;

    // Add a security handler for the credentials
    final Binding binding = bindingProvider.getBinding();
    List&lt;Handler&gt; handlerList = binding.getHandlerChain();
    if (handlerList == null) {
        handlerList = new ArrayList&lt;Handler&gt;();
    }

    handlerList.add(new RecordStream.SecurityHandler());
    // binding.setHandlerChain(handlerList);

    // Set the actual web services address instead of the mock service
    Map&lt;String, Object&gt; requestContext = bindingProvider.getRequestContext();

    requestContext.put(BindingProvider.ENDPOINT_ADDRESS_PROPERTY, &quot;http://&quot; + deviceip + &quot;/onvif/media_service&quot;);
    requestContext.put(BindingProvider.USERNAME_PROPERTY, user);
    requestContext.put(BindingProvider.PASSWORD_PROPERTY, pass);

    Recordings recordings = record_port.getRecordings();



The above code on run gives an error as:

    Exception in thread &quot;main&quot; javax.xml.ws.soap.SOAPFaultException: Method &#39;ns11:GetServiceCapabilities&#39; not implemented: method name or namespace not recognized

I also tried with media service, then the error is:

    Exception in thread &quot;main&quot; com.sun.xml.internal.ws.client.ClientTransportException: The server sent HTTP status code 405: Method Not Allowed


  [1]: http://www.openipcam.com/files/ONVIF/ONVIF_WG-APG-Application_Programmer%27s_Guide.pdf

Issue with recording from the Open ONVIF (Network Video Interface Forum ) device

I need to be able determine the path of the network Q drive at work for a WEBMethods project. The code that I have before is in my configuration file. I placed single character leters inside of the directories just for security reasons. I am not sure what the semi-colon is for, but I think that the double slashes are were the drive name comes to play.

Question: Is there an easy way on a Windows 7 machine to find out what the full path of the UNC is for any specific drive location?

Code:

    allowedWritePaths=Q:/A/B/C/D/E/
    allowedReadPaths=C:/A/B;//itpr99999/c$/A/FileName.txt
    allowedDeletePaths=

Find UNC path of a network drive?

When I ping an IP address, what is the difference between _Request timed out_ and _Destination host unreachable_ returned from the command?

ping response &quot;Request timed out.&quot; vs &quot;Destination Host unreachable&quot;

I&#39;ve got a browser game and I have recently started adding audio to the game. 

Chrome does not load the whole page and gets stuck at `&quot;91 requests | 8.1 MB transferred&quot;` and does not load any more content; and it even breaks the website in all other tabs, saying `Waiting for available socket`. 

After 5 mins (exactly) the data are loaded. 

![enter image description here][1]

![enter image description here][2]

This does not happen on any other browser.

Removing one MP3 file (the latest added one) fixed the problem, so is it perhaps a data limit problem?


  [1]: http://i.stack.imgur.com/ZutCF.png
  [2]: http://i.stack.imgur.com/FEW4q.png

Chrome hangs after certain amount of data transfered - waiting for available socket

I am using Amazon&#39;s tutorial for [installing a LAMP server][1]. The first several instructions involve using `yum`, but every single way I have tried to do it has resulted in the same message. I have found a few other recent questions about the same issue, none of which change anything on my setup.

Here is the message:

    Loaded plugins: priorities, update-motd, upgrade-helper
    Could not retrieve mirrorlist http://repo.us-east-1.amazonaws.com/latest/main/mirror.list error was
    12: Timeout on http://repo.us-east-1.amazonaws.com/latest/main/mirror.list: (28, &#39;Connection timed out after 10001 milliseconds&#39;)


    One of the configured repositories failed (Unknown),
    and yum doesn&#39;t have enough cached data to continue. At this point the only
    safe thing yum can do is fail. There are a few ways to work &quot;fix&quot; this:

     1. Contact the upstream for the repository and get them to fix the problem.

     2. Reconfigure the baseurl/etc. for the repository, to point to a working
        upstream. This is most often useful if you are using a newer
        distribution release than is supported by the repository (and the
        packages for the previous distribution release still work).

     3. Disable the repository, so yum won&#39;t use it by default. Yum will then
        just ignore the repository until you permanently enable it again or use
        --enablerepo for temporary usage:

            yum-config-manager --disable &lt;repoid&gt;

     4. Configure the failing repository to be skipped, if it is unavailable.
        Note that yum will try to contact the repo. when it runs most commands,
        so will have to try and fail each time (and thus. yum will be be much
        slower). If it is a very temporary problem though, this is often a nice
        compromise:

            yum-config-manager --save --setopt=&lt;repoid&gt;.skip_if_unavailable=true

     Cannot find a valid baseurl for repo: amzn-main/latest

I have done this same thing before without running into any problems, using the same tutorial, but it was several months ago. I don&#39;t know what has changed but my meager experience is keeping me from figuring it out.

  [1]: http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/install-LAMP.html

Amazon EC2 instance can&#39;t update or use yum

A guy I work with gave me the EC2 credentials to log onto his EC2 console. I was not the one who set it up. Some of the instances show a public dns name and others have a blank public DNS. I want to be able to connect to the instances that have a blank public DNS. I have not been able to figure out why these show up as blank.



EC2 instance has no public DNS

Is there any function to rename files and folders in Amazon S3? Any related suggestions are also welcome.

How to rename files and folder in Amazon S3?

We have a fairly simple node.js app, but due to AWS Elastic Beanstalk deployment mechanism, it takes about 5 minutes to roll-out a new version (via `git aws.push`) even after a single file commit.

I.e. the commit itself (and upload) is fast (only 1 file to push), but then Elastic Beanstalk fetches whole package from S3, unzips it and runs `npm install`, which causes node-gyp to compile some modules. Upon installation/building completion, Elastic Beanstalk wipes `/var/app/current` and replaces it with the new app version.

Needless to say, constant node_modules rebuilding is not necessary, and rebuilding that takes 30 seconds on my old Macbook Air, takes &gt;5 mins on a ec2.micro instance, not fun.

I see two approaches here:

 1. tweak `/opt/containerfiles/ebnode.py` and play with node_modules location to avoid its removal and rebuilding upon deployment. 
 2. set up a git repo on Elastic Beanstalk EC2 instance and basically re-write deployment procedure ourselves, so /var/app/current receives pushes and runs `npm install` only when necessary (which makes Elastic Beanstalk to look like OpsWorks..)

Both options lack grace and are prone to issues when Amazon updates their Elastic Beanstalk hooks and architecture.

Maybe somebody has a better idea how to avoid constant rebuilding of node_modules that are already present in the app dir? Thank you.

avoid rebuilding node_modules in elastic beanstalk

I&#39;m trying to write a query that count only the rows that meet a condition.

For example, in MySQL I would write it like this:

    SELECT
        COUNT(IF(grade &lt; 70), 1, NULL)
    FROM
        grades
    ORDER BY
        id DESC;

However, when I attempt to do that on Redshift, it returns the following error: 

ERROR: function if(boolean, integer, &quot;unknown&quot;) does not exist

Hint: No function matches the given name and argument types. You may need to add explicit type casts. 

I checked the documentation for conditional statements, and I found 

`NULLIF(value1, value2)`

but it only compares value1 and value2 and if such values are equal, it returns null. 

I couldn&#39;t find a simple IF statement, and at first glance I couldn&#39;t find a way to do what I want to do.

I tried to use the CASE expression, but I&#39;m not getting the results I want:

    SELECT 
        CASE
    	    WHEN grade &lt; 70 THEN COUNT(rank)
            ELSE COUNT(rank)
        END
    FROM
       grades

This is the way I want to count things:

 - failed (grade &lt; 70)
   
 - average (70 &lt;= grade &lt; 80)
   
 - good (80 &lt;= grade &lt; 90)

 - excellent (90 &lt;= grade &lt;= 100)

and this is how I expect to see the results:

    +========+=========+======+===========+
    | failed | average | good | excellent |
    +========+=========+======+===========+
    |   4    |    2    |  1   |     4     |
    +========+=========+======+===========+

but I&#39;m getting this:


    +========+=========+======+===========+
    | failed | average | good | excellent |
    +========+=========+======+===========+
    |  11    |   11    |  11  |    11     |
    +========+=========+======+===========+

I hope someone could point me to the right direction!

If this helps here&#39;s some sample info

    CREATE TABLE grades(
      grade integer DEFAULT 0,
    );
    
    INSERT INTO grades(grade) VALUES(69, 50, 55, 60, 75, 70, 87, 100, 100, 98, 94);

In Redshift/Postgres, how to count rows that meet a condition?

I want to delete a file from Amazon S3 using Javascript. I have already uploaded the file using Javascript. Any ideas?

How do I delete an object on AWS S3 using Javascript?

I know the whole design should be based on natural aggregates (documents), however I&#39;m thinking to implement a separate table for localisations (lang, key, text) and then use keys in other tables. However, I was unable to find any example on doing this. 

Any pointers might be helpful!

Content Type	Original Author	Original Content on Stackoverflow
Question	Daniel	View Question on Stackoverflow
Solution 1 - Performance	barbolo	View Answer on Stackoverflow
Solution 2 - Performance	Eric	View Answer on Stackoverflow
Solution 3 - Performance	chris	View Answer on Stackoverflow

What does amazon aws mean by "network performance"?

Performance Problem Overview

Performance Solutions

Solution 1 - Performance

Solution 2 - Performance

Solution 3 - Performance

Trim leading and trailing spaces from a string in awk

How to create constructor of custom view with Kotlin

Attributions