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Week 5 - Friday
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What did we talk about last time?
Simulation and modeling
Bioinformatics
If statements in Python
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Artificial intelligence (AI) is hard to define
 Trying to make machines think?
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Goals
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Problem solving
Representing knowledge
Creating machines that can learn
Natural language processing
Interpreting and interacting with the physical world and
humans
 Creativity
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General intelligence is perhaps the combination of all
these things
 Achieving general intelligence is sometimes called strong AI
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There are many approaches for generating
various aspects of artificial intelligence
 Simulating the human brain
▪ Like with Blue Gene
 Symbolic approaches
▪ Views all intelligence as manipulating symbols
 Sub-symbolic approaches
▪ Became popular in the 1980s
▪ Tries to process data without directly manipulating symbols
 Statistical approaches
 Combinations
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Neural networks are a popular
sub-symbolic tool
 They are composed of simple nodes
that take numerical inputs and add
them together with different
weights
 By adjusting the weights, you can
train a group of nodes to solve a
problem
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There are handwriting
recognizers and speech
recognizers that use neural
networks
i
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In the 1990s, statistical approaches became popular
For example, you can analyze language statistically
and
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Find rarely used words, are some of them misspelled?
Find buzzwords
Link different search terms together
Know that this phrase in Farsi is almost always translated
into that phrase in English
Most of Google's success in AI has been statistical
Like neural networks, statistical models of how
speech (or other intelligent behavior) is formed tend
to give us little insight into how intelligence works
 But they work!
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Alan Turing, a great early computer scientist, argued
that acting like a human being was proof of
intelligence
 In the Turing test, person A (call her Alice) texts with
entity B (call him Bob)
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 Bob could be a computer or a human
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If a computer can reliably fool Alice into thinking is a
human, it is displaying human intelligence
Alice: Are you a human?
Bob: What else would I be?
Alice: Do you like pie?
Bob: The value of pi is approximately 3.141592
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John Searle proposed an argument against symbolic AI
and the Turing test:
 Imagine a room filled with rules to manipulate symbols
 A man in the room receives symbols written on paper slipped
through a slot in the door
 He follows the rules, creates new symbols, writes them on
paper, and slips them back out the slot
 The symbols are actually Chinese characters
 Because the rules are complex enough, the Chinese speaker on
the outside believes that she is interacting with someone who
understands Chinese
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Does the man in the room understand Chinese?
Do our brains understand English or are they just
manipulating symbols?
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So, what about the evil AI we see in movies?
 Will Skynet take over the world?
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Computers are stupid
 They follow our instructions blindly (though quickly)
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Maybe some of the brain simulation research will
lead to a machine with human intelligence
At the moment, we are very far away
Some people like Ray Kurzweil think that change
will happen fast
If computers become intelligent enough to write
programs, who knows what could happen?
I'm not worried
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The most impressive feature of Siri is her voice
recognition
 Some is done on the device, some is done in the
cloud
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After that, some statistical work is done to
decide what your command or question
means
And how good is it?
For a limited set of commands that relate
directly to iPhone functions (playing songs,
calling contacts), it's great
Apple engineers put in some clever answers to
a few set questions
Otherwise, it gets disappointing fast
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The while loop runs as long as a condition is
true
countdown = 10
while countdown > 0:
print(countdown)
countdown = countdown – 1
print("Blast-off!")
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In this case, when countdown becomes 0, the
loop stops (since 0 is not less than 0)
Note that while loops use the same relational
operators as if statements
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If you want to do something, say, 10 times in
Python, you can use a for loop
But you need to call the range() method to
generate a list of numbers for you
for i in range(10):
print(i)
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In this case, the loop will run 10 times, and
the numbers 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9
will print out
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In Python, the primary way to make a choice is with
an if statement
if phrase == "open sesame":
print("Welcome, Ali Baba!")
else:
print("Access denied!")
Whatever code is under the if and tabbed in will only
be executed if the condition is true
 Optionally, an else section can be added if you want
to do something if the condition is false
 Conditions often use the following relational
operators to make a comparison: ==, !=, <, <=, >, >=
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The if and else constructs allow us to
choose between two possibilities
What if we wanted more?
We can extend these constructs with elif to
handle additional conditions
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elif is short for "else if"
It's used when the prior condition wasn't true
and we want to check another condition
if number == 1:
print("First")
elif number == 2:
print("Second")
elif number == 3:
print("Third")
else:
print(number + "th")
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The elif construct if used if you want a
bunch of mutually exclusive outcomes
Only one of the choices is possible
It is very common to end a sequence of if,
elif, elif, elif, … statements with an
else, whose code will be executed if none of
the previous cases was true
However, the else is not used if there's
nothing to be done when no case matches
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Graph theory
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Start working on Project 2
Read Python Chapter 5