Image Recognition with TensorFlow – python

1. Start with this link https://www.tensorflow.org/tutorials/image_recognition#usage_with_python_api
2. Download TensorFlow models repo from Github here https://github.com/tensorflow/models/blob/master/inception/inception/image_processing.py
3. If you got errors with python, go here https://stackoverflow.com/questions/40357548/inception-v3-guide-on-tensorflow-broken-for-c-and-python
   or
   https://github.com/samjabrahams/tensorflow-on-raspberry-pi/issues/47
4. Remove the argv command

Installing TensorFlow on MacOS Sierra

I can’t remember every steps but I need to leave some notes that I can refer to later 🙂 I just put everything I can remember here 🙂

The directory:

cd /usr/local/lib/python2.7/site-packages/tensorflow/bin
source activate tensorflow

code example to test

>> import tensorflow as tf
>>> hello = tf.constant(‘Hello, TensorFlow!’)
>>> sess = tf.Session()
>>> print sess.run(hello)
Hello, TensorFlow!
>>> a = tf.constant(10)
>>> b = tf.constant(32)
>>> print sess.run(a+b)
42
>>> quit()
(tensorflow) CG-MacBook-Pro-2:bin Marisa$ deactivate

Activating virtualenv

$ cd /path/to/tensorflow/bin
$ source activate tensorflow
$ python
>>> import tensorflow as tf
>>> print(tf.__version__)
1.0.1

Important links:

1. https://www.tensorflow.org/install/install_mac#the_url_of_the_tensorflow_python_package
2. https://thkim.org/tensorflow/tensorflowinstallation/tensorflowinstallationvirtualenv/
3. https://github.com/tensorflow/tensorflow/issues/647
4. https://codedump.io/share/6Oq22H5Uhoab/1/virtualenv-tensorflow-instalation-validation-with-importerror-no-module-named-tensorflow
5. https://stackoverflow.com/questions/43647090/virtualenv-tensorflow-installation-validation-with-importerror-no-module-named
6. http://python-guide-pt-br.readthedocs.io/en/latest/dev/virtualenvs/
7. https://hackercodex.com/guide/python-development-environment-on-mac-osx/
8. http://sourabhbajaj.com/mac-setup/Python/virtualenv.html

The journey:

Downloading TensorFlow

Install and update

Removing Anaconda

tensorflow library couldn’t be recognized. Installing gpu version

installing for python 2.7

reinstalling python and fixing the PATH

installing virtualenv

installing tensorflow on virtualenv

tensorflow had been successfully installed on virtualenv

tensorflow library still not recognized

finally figure out how to activate the virtualenv

library recognized but there were errors!

reinstall tensorflow to the activated virtualenv, and it worked!

YES!!! 🙂 Now I’m ready to explore! 😉

Fixing Java that cannot be re-installed after being uninstalled

One of our computer,  on 64-bit Windows 7,  being used for Minecraft programming using CanaryMod and Scriptcraft so the coding can be done in JavaScript, having troubles after we did so much modding so we had to uninstall the (32-bit) Java.

The problem was that Java could not be reinstalled because the uninstalling process was not clean so that Java files were still in the registry, made the Java installer thought that Java was already installed.

We have download like ten registry cleaner software, tried 3 or 4 of them but the problem remained. Until we find a very useful ilnk that finally made the installation work.

The trick is to type <pre><code>regedit</code/</pre> on Windows start menu and then find any folder contains Java on the folder under <pre><code>HKEY_LOCAL_MACHINE\SOFTWARE\CLASSES\INSTALLER\PRODUCTS</code></pre>. This is a bit tedious but it is totally worth it 😀

After that delete these to folder:

<pre><code>HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment</code></pre>

<pre><code>HKEY_LOCAL_MACHINE\SOFTWARE\wow6432node\JavaSoft\Java Runtime Environment</code></pre>

and then all will be set and the installation will be done just fine.

Installing RabbitMQ on MacOS

1. Download RabbitMQ for Mac here
2. Download Java AMQP client library here
3. Start RabbitMQ server by running ./rabbitmq-server
4. Check that the server is running properly with ./rabbitmqctl status
5. Compile and run a HelloWorld testing program from the tutorial here. Compile the Send.java and Recv.java files with javac -cp rabbitmq-client.jar Send.java Recv.java. Run Send.java with java -cp .:commons-io-1.2.jar:commons-cli-1.1.jar:rabbitmq-client.jar Send. This will send the message (in this case the message is “Hello World!”) to the queue. And then run Recv.java with java -cp .:commons-io-1.2.jar:commons-cli-1.1.jar:rabbitmq-client.jar Recv to pop out the message on the queue.
6. The server and the queues can also be checked via browser http://localhost:15672/

Now the queue is ready.

How to run Minecraft on Mac OS X Yosemite 10.10.1

I got this message when running Minecraft on Yosemite, and when I googled I found that this is common problems.

Some references say that the latest JDK should be installed while the earlier ones should be uninstalled. I have uninstalled the earlier and installed the latest JDK but the problem persisted.

So I followed this reference to make it work.

These are the steps:Install ant

1. Download Java Application Bundler
2. Download Minecraft.jar from here *after clicking “Show all platforms” and choose that one under “Linux and Other
3. Create a file named build.xml and type this code in
   
4. Organize my file like this
   
   *Notes: at this point, the dist folder is empty, it will contain Minecraft.app after I run ant command*
5. Open terminal and run ant like this
   
6. Now the dist folder will contain Minecraft.app in it. Move it to Applications folder

And it works!

My next step is to make canarymod and scriptcraft work to make mods on Minecraft. Wish me luck.

Convolutional Code

Unlike block codes, convolutional codes does not send the message followed by (or interspersed with) the parity bits. In a convolutional code, the sender sends only the parity bits.

The encoder uses a a sliding window to calculate r > 1 parity bits by combining various  subsets of bits in the window. The size of the window, in bits, is called the code’s constraint length. the longer the constraint length, the larger to number of parity bits that are influenced by any given message bit. Because the parity bits are the only bits sent over the channel, a larger constraint length generally implies a greater resilience to bit errors. The trade-off is that it will take more time to decode codes for more constraint length.

If a convolutional code that produces r parity bits per windows and slides the window forward by one bit at a time, its rate is 1/r. The greater the value of r, the higher the resilience of bit errors, but the trade-off is that a proportionally ginger amount of communication bandwidth is devoted to coding overhead. In practice, it is more commen to pick 4 and the constraint length to be as small as possible while providing a low enough resulting probability of a bit error.

This is an example of a convolutional code with rate 1/2:

This is a systematic 1/3 encoder:

And this is a 2/3 encoder:

To make the convolutional code able to cope with more errors, it is not by changing the k or n (r = k/n). But by adding more memory inside the encoder (the square with D letter). Notes that all the circles with plus symbol (or the xor process) is the generator functions to determine each output. It works just like other generator of other error correction codes.

This is the Trellis Diagram of the first convolutional code:

Trellis Diagram is a graph whose nodes are ordered into vertical slices (time), and with each node at each time connected to at least one node at an earlier and at least one node at a later time. The earliest and latest times in the trellis have only one node.

This diagram gives “spatial” and “temporal” information about the code. “Temporally” it shows the state on each t while “spatially” it shows every possible route defined by the encoder design. Later, the decoding would be done by comparing the received “route” with the “most likely route” to track down the error and then correct it.

Viterbi is a scheme for decoding, using maximum likelihood decoding that set up a threshold to check the “route” with the “deviated route”.

References:

1. MIT 6.02 DRAFT Lecture Notes, Fall 2010 (Last update: October 4, 2010)
2. http://en.wikipedia.org/wiki/Trellis_(graph)
3. “Error Control Coding”, Shu Lin and Daniel J. Costello

Amdahl’s Law and Price Elasticity

I have just noticed that Amdahl’s Law used in measuring processor performance is similar with the Price Elasticity Law (I read from the book “Starbucks (Corporations that Changed the World) – Marie Bussing-Burks”) in economic concepts.

The same principle is that there is a limit in increasing processing performance to get more throughput, or to rephrase it in business language: there is a limit in reducing price of an item to get more revenue.

Amdahl’s Law says that speedup is how a machine performs after enhancement. A SpeedUp(E) = Performance with E / Performance without E = Execution time without E / Execution time with E. Execution time = Execution time unaffected + (Execution time with E / Amount of improvement).

(Notes: Examples is taken from EL 2244 Course being taught at ITB this semester. The reference book is John L. Hennessy and  David A. Patterson , Computer Organization and Design: The Software Hardware Interface, Morgan Kaufmann Publishers, 4th Edition, 2009.)

Ex. 1:

A program runs in a machine in 10s. 50% of the time is doing multiplications. If we improve the multiplication unit so it runs twice as fast, how big is the speed up?

Answer:

Exec_time(E) = (Affected_exec_time/improvement) + unaffected_exec_time

= (5s/2) + 5s = 7,5 s

Speed_up(E) = 10s/7,5s = 1,333  which is not 2 times faster

Ex. 2:

A program runs for 10s. 70% of the time is doing additions. How much improvement on the additions if we want to reduce the running time to 3s?

Answer:

Exec_time(E) = (Affected_exec_time/improvement) + unaffected_exec_time

3s = (7s/n) + (10-7)s

3s = (7s/n) + 3s

0 = 7s/n

No amount of improvement can reduce the running time to 3s.

Now let’s see the Price Elasticity Law. Price Elasticity (E) = % change in quantity demand / % change in price.

Ex 1:

If we reduce the price of 36 inch TV from $450 to $400, the average price would be $425. The absolute value of percentage change = $50/$425 = 0.118. Number of unit sold is increased from 200 to 300 so the average number of unit sold = 250.

So the percentage  of change in quantity demand is 100/250 x 100% = 40%.

The price elasticity = 0.4/0.118 = 3.39%

If the absolute value of price elasticity is between 0 – 0.99, demand is inelastic. Necessity items like coffee, milk, gasoline, prescription drugs are tend to be relatively insensitive to price change.

Ex 2:

A store manager drops the price of a gallon of milk from $4 to $3. The average price will be $3.5. The absolute value of % change = $1/$3.5 = 0.29

Milk sold going from 10 to 11. The average number of gallon sold = 10.5. Percent of change in quantity demand = 1/10.5 = 0.1.

Price elasticity = 0.1/0.29 = 0.34. The demand is inelastic.

So if demand is elastic, a price cut will increase total revenue (and an increase in price will mean lower total revenue). If we take Ex 1:

price x quantity = total revenue

$450 x 200 = $90,000

$400 x 300 = $120,000

While when demand is inelastic, a price cut will decrease total revenue. As in Ex 2:

$4 x 10 = $40

$3 x 11 = $33.

The conclusion is that in terms of machine performance and total revenue, there is a limit to get “improvement”. There is a certain point that we cannot further improve the speed of a machine as well as there is a certain point that we cannot change price to get more total revenue.

Reed Solomon – A Brief Introduction

Reed Solomon is one brilliant error correction method that is a non-binary cyclic codes. The codeword looks like the picture below. It has symbols in m-bits. The bit string is treated as a group of bits. The group of bits is treated as non-binary. We will see how it makes this method powerful.

Let’s take an example of RS(15,11). This means that we have the codeword with length 15 bits that consists of original message 11 bits  and 4 bits for parity. t is how many errors (in symbols or group of bits) that can be corrected.

p(x) or irreducible polynomial is used to generate the finite field like shown in the table below.

Now we need a generator to start the encoding process.

The process of decoding includes several steps. Let’s take an example of double-symbol error.

The first process is computing the syndrome to detect the error. For this case will have 4 syndromes: S1, S2, S3 and S4. Each S that is not equal to 0 contains error.

The second step is locating the error in e(x). This can be done using matrix.

After the location has been determined, now it is the time to calculate the values of the error so we can correct the error.

Done. We get the message corrected. Do you notice that detecting the errors in symbols (groups of bits) in this method makes it runs faster?

2013 in review

The WordPress.com stats helper monkeys prepared a 2013 annual report for this blog.

Here’s an excerpt:

The concert hall at the Sydney Opera House holds 2,700 people. This blog was viewed about 17,000 times in 2013. If it were a concert at Sydney Opera House, it would take about 6 sold-out performances for that many people to see it.

Click here to see the complete report.

PhoneGap – Getting Started using Xcode

1. Download and install NodeJS and PhoneGap
2. Type this in Terminal: (make sure you have a stable internet connection because this will affect the generation of the code like missing libraries, invalid structures of directories etc.)
   
   You have to do this project creating and building on command prompt because in later versions of XCode, they do not give you to choose Cordova application or PhoneGap application when you start a new project like shown in this picture:
   
3. Find the .xcodeproj and run it (it will be opened automatically in XCode)
   
4. And then Run the project (by pressing the button on the top left) and you will get this
   
   You can modify the index.html or .js scripts and see how they look in simulator.An error usually occurs (the error message would be “index.html not found” when there is no index.html in www directory or the structure of the directory is not like shown below.

Note:

1. The version I’m using is Xcode 5.0, iOS Simulator 6.1, PhoneGap 2.9.0 and node.js v0.10.20. Running on Mountain Lion 10.8.5
2. If you are using different versions in either of one of them, the result might be slightly different