Optional: Follow the instructions to verify the download (you might need to get GNU Privacy Guard or gpg for this. You can get it at http://gnupg.org)
Say it’s downloaded to your “Downloads” directory, go there and execute the following commands (using the terminal)
cd ~/Downloads
tar -xzf glpk-4.43.tar.gz
./configure —prefix=/usr/local # see note 1
make
sudo make install
At this point, you should have GLPK installed. Verify it:
which glpsol
/usr/local/bin/glpsol
So here’s my simple implementation: (or as a gist on github)
module RussianPeasantMultiplication
def russian_peasant_multiply(b)
numbers_to_add = []
a, b = [self, b].sort #So we have the smaller number as the first
negative_operands = [a, b].select { |n| n < 0 }
result_should_be_negative = negative_operands.size.odd? # or negative_operands.size == 1
# Now get the absoultes
a, b = [a, b].map { |n| n.abs }
while( a > 1 )
a = a >> 1 # halv it
b = b < < 1 # double it
if a.odd? # or (a % 2 == 0 )
numbers_to_add << b
else
end
end
result = numbers_to_add.inject(0) { |sum, n| sum += n }
result = result * -1 if result_should_be_negative
result
end
end
class Integer
include RussianPeasantMultiplication
end
# Tests
require "test/unit"
class TestInteger < Test::Unit::TestCase
def test_russian_peasant_multiply
assert_equal(22 * 70, 22.russian_peasant_multiply(70))
end
def test_russian_peasant_multiply_for_negative_numbers
assert_equal(-22 * 70, -22.russian_peasant_multiply(70))
end
def test_russian_peasant_multiply_for_negative_arguments
assert_equal(22 * -70, 22.russian_peasant_multiply(-70))
end
def test_russian_peasant_multiply_for_negative_numbers_and_arguments
assert_equal(-22 * -70, -22.russian_peasant_multiply(-70))
end
def test_russian_peasant_multiply_for_zero
assert_equal(0 * -70, 0.russian_peasant_multiply(-70))
end
def test_russian_peasant_multiply_for_zero_arguments
assert_equal(-22 * 0, -22.russian_peasant_multiply(0))
end
def test_russian_peasant_multiply_for_zero_numbers_and_arguments
assert_equal(0 * 0, 0.russian_peasant_multiply(0))
end
end
Pics from the Colorado trip back in November, 2009 (with Ujwala and Maa). We spent two days in Rocky Mountain National Park and a day over in Colorado Springs and around (Manitou Springs, Pikes Peak – highest peak in that area).
It’s heavenly – have to go there again in Spring 2010 )along with the parks in Wyoming, Montana).
Click on the photo to get to my SmugMug page – feel free to leave a comment
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Figured this out after a lot of monkeying-around (I mean script/console).
Situation:
I have two tables (Revisions has_many Inputs)
I can load Revisions and then for each I can find Inputs, but quickly found out that for my situation, it leads to a lot of queries. So I want to load the required fields from both tables together
:joins is the only way to do this, using :includes does NOT respect the select clause. Here a gist:
Admittedly, this is hacky, too hacky for my comfort. Comment/suggest a better/cleaner solution?
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