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+Optimize keyboard layout
+========================
+:CreationDate: 2003-01-28 10:09:25
+:tags: - software
+       - keyboard
+
+I'm sure you, too, know the history of the Sholes ("QWERTY") keyboard,
+that was designed to avoid that too fast typists jammed mechanical
+typewriters. You would know also that the Dvorak layout is cosidered
+by many to be faster and more effective.
+
+When I tried to learn to use the Dvorak keyboard, a friend of mine
+asked me: «Why don't you write a program to measure your keyboard
+usage, and then obtain a personalized layout?». In a moment of
+crazyness, I decided to do just that.
+
+The first program is freq.pl_, which reads the files given on the
+command line and produces a probability matrix, writing it into the
+file whose name is in the ``$MATRFN`` variable, default
+``/tmp/freq.matr``. Actually it sees the text as a Markov process over
+the characters with memory 1, and extracts the transition
+matrix. Note: the elements are frequencies, not probabilities. The
+optional normalization is left as exercise to the reader.
+
+The second program is freqdump.pl_, which is probably
+useless. I've written it (three or four different versions) to have an
+idea about the frequencies. Give it a look if you want.
+
+The most useful program (I hope) is optkeyb.pl_, which starting
+from the matrix (as usual, filename hardcoded) and the QWERTY layout
+searches by stochastic gradient descent a better layout. In other
+words, it calculates a value for the layout (sum over the pairs of
+keys of their distance times the frequency of that pair), then tries
+to exchange two random keys looking for a better result.  To avoid
+local minima (there are a lot) it starts by randomly exchanging
+``$PRE_SHUFFLE`` pairs, and if it doesn't find a better layout for
+``$STARVATION`` tries it starts again, after having written the
+locally optimum layout at the end of the file ``/tmp/layouts``. It
+uses curses and the corresponding Perl module ``Curses.pm``.
+
+To avoid bad things, like numbers scattered between other keys, it's
+possible to set into the ``%locked`` hash the keys that must not be
+moved.
+
+To give yoy an idea of the results, after some hours of computation
+the best layout was::
+
+    ` 1 2 3 4 5 6 7 8 9 0 ; =
+       - x w h t s a l b y ' j q
+       z \ [ c i e r u p . ,
+        k v f d n o m g ] /
+
+Bear in mind I use a IBM U.S. keyboard, and where the ``q`` is,
+there's usually the backslash/pipe key, which is larger than the
+others, so I should have locked it...
+
+To have an idea of the optimization, the value relative to the QWERTY
+layout is 10.190.280, for the one above is 6.797.370, meaning a 34%
+reduction in the space travelled by the fingers during writing.
+
+.. _`freq.pl`: /src/freq.pl
+.. _`freqdump.pl`: /src/freqdump.pl
+.. _`optkeyb.pl`: /src/optkeyb.pl