Play Time. When we allow ourselves to be spontaneous or creative, playfully enjoying novel experiences, which helps make new connections in the brain.

Connecting Time. When we connect with other people, ideally in person, or take time to appreciate our connection to the natural world around us, richly activating the brain’s relational circuitry.

Physical Time. When we move our bodies, aerobically if medically possible, which strengthens the brain in many ways.

Time In. When we quietly reflect internally, focusing on sensations, images, feelings and thoughts, helping to better integrate the brain.

Down Time. When we are non-focused, without any specific goal, and let our mind wander or simply relax, which helps our brain recharge.

Sleep Time. When we give the brain the rest it needs to consolidate learning and recover from the experiences of the day.

Excerpted from: http://www.psychologytoday.com/blog/your-brain-work/201106/announcing-the-healthy-mind-platter

I tried out linuxmint-11-gnome-cd-nocodecs-32bit and linuxmint-xfce-201104-dvd-32bit today, and was not impressed.  Ok, I was actually impressed once I got it to run, but only before the launcher crashed and asked to be restarted.  And then it was all down hill.  I couldn’t even get the installer to run the first time around.  I tried again with the Xfce DVD version.  This installer ran just fine, but then 800 updates required (ok, no biggie, very common).  I click to apply updates, but then I’m confronted with a package dependency error, and told to resolve dependencies first.  Next, I try to install just one thing at a time.  First up: the mint-welcome package. Does that install? Click -> Apply -> ok.  Looks like it was fine.  Next up, some other mint package, I don’t recall.  Anyway, this one caused the updater to crash.  Reboot, try again, crash again.  You know what? I don’t have all day.

Let’s try out the internet… open firefox, head to youtube for the obligatory flash test.  Video starts playing… it’s an ad.  Well, about 4 seconds before the ad finishes, the video freezes.  Page refresh: Replay the ad, and that 4 second video freeze problem again.  Ok, that means that flash support is buggy.  Well, remember how I can’t update anything with the updater software? That means I’m stuck.  I don’t feel like wading through individual packages to get this thing working.  I want a Minty out-of-box experience.  What I got was roach infested.

LSS (Long-Story-Short), save yourself the effort, just go xubuntu (for the xfce type).

The long and short of it is to set up a local SOCKS5 proxy with putty. Simply open up putty, go to Connection>SSH>Tunnels. Add a new forwarded port (say 1080), make it dynamic, then hit add. Now log in to your remote machine and you have a local SOCKS5 proxy running on port 1080. You can then point your browser to use this proxy for all your web traffic.

The link also mentions how to make Firefox tunnel DNS requests for added security, but I won’t go into that.

Happy safe browsing!

List comprehension:

Create a list from a function and filter:

S = [2*x for x in range(101) if x**2 > 3]

Generator

Define a generator:

from itertools import count
 
def generate_primes(stop_at=0):
    primes = []
    for n in count(2):
        if 0 < stop_at < n:
            return # raises the StopIteration exception
        composite = False
        for p in primes:
            if not n % p:
                composite = True
                break
            elif p**2 > n:
                break
        if not composite:
            primes.append(n)
            yield n

Using a generator:

for i in generate_primes():  # iterate over ALL primes
    if i > 100:
        break
    print i

map (source):

def cube(x): return x*x*x
map(cube, range(1, 11))  # outputs [1, 8, 27, 64, 125, 216, 343, 512, 729, 1000]

seq = range(8)
def add(x, y): return x+y
map(add, seq, seq)  # outputs [0, 2, 4, 6, 8, 10, 12, 14]

reduce (source):

def add(x,y): return x+y
reduce(add, range(1, 11))  # outputs 55

filter (source):

def f(x): return x % 2 != 0 and x % 3 != 0
filter(f, range(2, 25))  # outputs [5, 7, 11, 13, 17, 19, 23]

iter (source):

for value in sequence:
    print(value)

for key in dictionary:
    value = dictionary[key]
    print(key, value)

for key, value in dictionary.items():
    print(key, value)

range (source):

a = ['Mary', 'had', 'a', 'little', 'lamb']
for i in range(len(a)):
    print i, a[i]

xrange (source):

z = lambda x, h: [sum((x[i - j] if (0 <= i - j < len(x)) else 0) * h[j] \
for j in xrange(len(h))) \
for i in xrange(len(x) + len(h) - 1)]

Decorators:

class C(object):
 
    @staticmethod
    @funcattrs(grammar="'@' dotted_name [ '(' [arglist] ')' ]",
               status="experimental", author="BDFL")
    def longMethodNameForEffect(longArgumentOne=None,
                                longArgumentTwo=42):
        """This method blah, blah.
 
        It supports the following arguments:
        - longArgumentOne -- a string giving ...
        - longArgumentTwo -- a number giving ...
 
        blah, blah.
 
        """
        raise NotYetImplemented

Strategy Pattern:
Example usage:

class Button:
    """A very basic button widget."""
    def __init__(self, submit_func, label):
        self.on_submit = submit_func   # Set the strategy function directly
        self.label = label
 
# Create two instances with different strategies
button1 = Button(sum, "Add 'em")
button2 = Button(lambda nums: " ".join(map(str, nums)), "Join 'em")
 
# Test each button
numbers = range(1, 10)   # A list of numbers 1 through 9
print button1.on_submit(numbers)   # displays "45"
print button2.on_submit(numbers)   # displays "1 2 3 4 5 6 7 8 9"

See documentation for:

• itertools
• functools

This post was inspired by an item on StackOverflow: Python Progression Path from Apprentice to Guru

Background
Using DCF analysis to compute the NPV takes as input cash flows and a discount rate and gives as output a price; the opposite process – taking cash flows and a price and inferring a discount rate, is called the yield.

Definitions
FV = DPV * (1+i)^n
DPV = FV/(1+i)^n = FV * (1-d)^n

DPV: discounted present value
FV: future cash flow; nominal value of cache flow in future
i: interest rate
d: discount rate { i/(1+i) } ; interest rate subtracted from BoY; rather than added at end of year
n: time in years before future cash flow

Summing multiple cash flows:
DPV = SUM{t=0..N} of { FV[t]/(1+i)^t }

An Example
“John Doe buys a house for $100,000. Three years later, he expects to be able to sell this house for $150,000.”

“the 3-year US Treasury Note rate is 5% per annum.”

“Using the DPV formula (FV=$150,000, i=0.05, n=3), that means that the value of $150,000 received in three years actually has a present value of $129,576 (rounded off).”

“Subtracting the purchase price of the house ($100,000) from the present value results in the net present value [(NPV)] of the whole transaction, which would be $29,576…”

“Another way of looking at the deal as the excess return achieved (over the risk-free rate) is (14.5%-5.0%)/(100%+5%) or approximately 9.0% (still very respectable). (As a check, 1.050 x 1.090 = 1.145 approximately.)”

So, I’m still n00b status, but here’s the deal: It’s got all the things I love about Javascript, the good parts of Java (no bloat), and the fundamental simplicity of C. PHP is conspicuously absent here, but … now that I mention it, there’s something there too.

Let’s over go over those, since you may be flaming me already. Hey! I’m still a n00b.

Javascript I really like the function mapping aspects. Ok, so this is more of a jQuery-type thing. But it’s possible, and jQuery makes it obvious — in-your-face — how useful this feature is. I could care less about lambda functions right now, but I think they’re related. I like the way zip() works on arrays.

Java Ah, the language of verbosity. I’d rather dictate War and Peace, than write Java. What’s so good about Java? It’s got a great package system, and the try/catch/finally construct. Python’s equivalent: try/except/finally. Thumbs up! Java has a good class hierarchy that Python seems to duplicate (minus the Java overhead).

C There’s nothing more powerful than C. Assembly’s got nuthin’ on C. C is the ultimate speed-speed trade-off. The speed of code development vs the speed of execution. Everything else is derivative bloat that hinders performance. So, how does Python act like C? Well, the BDFL gives Python a coherent structure. The Java package sprawl problem is not present. Code bases are tight. Syntax is rigid. Writing Python is like clock-work — it must be precise.

PHP Don’t flame. Here it is. Python is extra-great because it’s interpreted. PHP is interpreted. That is all.

Confusion says: The n00b walks a fine line of asking and testing. Nobody ever said learning a language was easy. It should be fun (or interesting if you don’t like learning) though! So here’s the deal: I’m not flying yet. I’m tutorializing. Short programs are useful learning tools, but jumping in the deep end really makes you sink or swim — strangely, I’m trying to be trite right now. I don’t get lambda. I don’t know why there are so many different types of lists. I know I’ve had a need for sets, lists, hashes, tuples, queues, and the like, but is it really necessary that there be a specific data type for each? Whatever, I’m a n00b. I know performance is probably the real motivator, but c’mon! It’s interpretive. I was surprised to learn that compiled Python (.pyc) does not execute any faster than inline Python (.py) (Can’t find the reference). The .pyc files make the module load faster, not execute faster.

Anyway, right now, Python makes a great calculator. Anyone living in Hawai’i will tell you the numerous “spam and eggs” references make’s ‘em hungry too!

If this is you:

...edit files...
git add edited-file
git commit -m "made changed"
git rm seemingly-useless-file
git commit -m "removed unreferenced dependency"
... edit file ... realize you dynamically included that file elsewhere..

Then you can simply follow up with:

git checkout 0a323 // the previous revision (hash from `git log`)
cp seemingly-useless-file seemingly-useless-file.1
git checkout master
mv seemingly-useless-file.1 seemingly-useless-file
git add seemingly-useless-file
git commit -m "Restored seemingly-useless-file"

You may want to git blame yourself while you’re at it.

If you know of a better way, please let me know.

There are several known branches of this problem.

One involves the Google Earth browser plug-in:

Apparently, this incorrect handling is the end result of a bug fix to “correct” icon heading behavior.
Google Earth Plug-in – 5.1.3506.3999

(Issue 131) Icon headings should now behave as expected, and consistent with the Google Earth desktop client. http://www.noeman.org/gsm/mac-other-oses-softwares/106515-google-earth-google-earth-plug.html

More on this bug (affecting version 5.1.x): http://www.google.com/support/forum/p/earth/thread?tid=005bea9c26949e40&hl=en

Work-arounds: GroundOverlay and use a Colada model, both ugly.

Another instance of the icon heading bug:
There is another situation in which the heading of the icon is not obeyed. This occurs when an invalid styleUrl is used in the KML. One recommendation is to remove the “#” character. ex: <styleUrl>#balloonStyle</styleUrl> is no longer correct as of version 5x. I have not confirmed this, but I’ve heard that this is correctly implemented as <styleUrl>balloonStyle</styleUrl>. What happend? This isn’t very backwards-compatible nor user-friendly. Why the change? HTML hashes are logically sound, as they refer to a locally named entity, such as those specified by a style id.

What worked for me was to completely remove the styleUrl when providing a local Style. See below.

Broken:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52

<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://www.opengis.net/kml/2.2" xmlns:gx="http://www.google.com/kml/ext/2.2" xmlns:kml="http://www.opengis.net/kml/2.2" xmlns:atom="http://www.w3.org/2005/Atom">
<Document>
 <name>Weather Stations</name>
 <description><![CDATA[<p>Generated: 2010-01-19 22:03:45 UTC</p> <p>Only stations reporting <b>within 3 hours</b> are included in this document.</p>]]></description>
 <open>1</open>
 <Style>
  <ListStyle>
   <listItemType>radioFolder</listItemType>
   <bgColor>00ffffff</bgColor>
   <maxSnippetLines>2</maxSnippetLines>
  </ListStyle>
 </Style>
 <Style id="balloonStyle">
  <BalloonStyle>
   <text><![CDATA[
   <h2 style="font-size:1.1em;border-bottom:solid #333 1px;">Instrument:
   $[name]</h2>
   $[description]
   ]]></text>
  </BalloonStyle>
 </Style>
 <Folder>
  <name>Visibility and Avg Winds</name>
  <Style>
   <ListStyle>
   <listItemType>checkHideChildren</listItemType>
   <bgColor>00ffffff</bgColor>
   <maxSnippetLines>2</maxSnippetLines>
  </ListStyle>
 </Style>
 <visibility>0</visibility>
 <Placemark>
  <name>Any Instrument ID</name>
  <description><![CDATA[ <p><font color="#999">Sample Date</font></p> <div>Data Table Here</div>]]></description>
  <styleUrl>#balloonStyle</styleUrl>
  <Style>
   <IconStyle>
    <scale>3.25</scale>
    <heading>0</heading>
    <Icon>
     <href>http://www.example.com/barb.php?spd=4&amp;dir=74&amp;val=7&amp;col=65280&amp;dia=100</href>
    </Icon>
   </IconStyle>
  </Style>
  <Point>
   <coordinates>-117.1135,32.3325,0</coordinates>
  </Point>
 </Placemark>
 </Folder>
</Document>
</kml>

Working:

33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48

 <Placemark>
  <name>Any Instrument ID</name>
  <description><![CDATA[ <p><font color="#999">Sample Date</font></p> <div>Data Table Here</div>]]></description>
  <Style>
   <IconStyle>
    <scale>3.25</scale>
    <heading>0</heading>
    <Icon>
     <href>http://www.example.com/barb.php?spd=4&amp;dir=74&amp;val=7&amp;col=65280&amp;dia=100</href>
    </Icon>
   </IconStyle>
  </Style>
  <Point>
   <coordinates>-117.1135,32.3325,0</coordinates>
  </Point>
 </Placemark>

Kids today get emo and suicidal because they have been given everything, never had to earn anything, never been hungry, never had anything real to fear, never been punished for their behavior and are bored with having too much entertainment. Nadaka

Question: How can you determine when 45 minutes have elapsed?

Answer: Light one rope at both ends. Light the other rope at only one end. When the rope that was burning from both ends has burnt out, 30 minutes have passed. Light the second end of the rope that was only burning from one end. This rope will burn out in 15 more minutes. The total time will have been 45 minutes.

Reference:

• How to Kill MySQL Performance

I wish that this noble statement were true for me as well, but that’s not often the case. When I try to be humble, I spare the details, often at great expense to the lesson. When I try to be overly showy, I don’t get to the point.

In just the past month alone, I have been hesitant to write out my thoughts, and have lost any possibility of pursuing those endeavors further, as I can no longer remember them. I failed to ask questions in fear of projecting uncertainty. What I have succeeded at doing is completely passing on the opportunity to reflect later on.

I don’t write because I don’t re-read. This post has already grown so long. Will I read it later? So let the lesson be this: Write often, write succinctly, and reflect.

Resolution

Using the MySQL command-line tool:

mysql -u admin -p [-h ] [-P ]
mysql> flush hosts;


That’s it!

Chain of Events

• UCSD’s DNS was polluted, identifying 132.239.123.144 as ridge2000.org for the past few weeks.
• Sandbar was restarted last week, freeing up both the OS and MySQL DNS caches, which meant all new connections will need to query a DNS server to identify whether it’s an allowed machine or not (do you see a security vulnerability?).
• Both the OS and MySQL cached the hostname, but MySQL further rejected all connections from alfredo because MySQL thought that alfredo was ridge2000 instead.
• The mysql database, user table identifies user sccoos can connect to sandbar from alfredo.ucsd.edu.
• The OS cache probably cleared, but since so few machines access sandbar, the MySQL cache hadn’t filled up yet.
• Just last night (2008-12-22), the UCSD DNS purged the ridge2000.org name from its list, so UCSD’s DNS is clean, but any caches may still be polluted.

• Windows machines cycle their caches regularly, so the problem isn’t more wide-spread or commonly understood.
• The long-lasting MySQL DNS cache is disturbing, but alternatives would cripple the imperative nature of a database.

References

• MySQL DNS Reference
• Domain Name System