@@ -1,7 +1,8 @@
 # Compiled languages
 *.o
-# Must be in src, because those in data should be included.
+# Must be in src, because the `.out` in data/ should be included.
 /src/**/*.out
+gmon.out
 
 # Java
 *.class
 
@@ -43,12 +43,16 @@ Easy to state, hard to prove.
 
 Many other analogous questions like PSPACE vs NP.
 
+### Computability
+
 ### Undecidability
 
 <http://en.wikipedia.org/wiki/Undecidable_problem>
 
 Mysterious feeling: there are problems that you can state, but not solve in general.
 
+A recursive definition of computable for integer functions: <https://en.wikipedia.org/wiki/Primitive_recursive_function#Relationship_to_recursive_functions> Famous counter example which removes the "Minimisation operator": <https://en.wikipedia.org/wiki/Ackermann_function>, and falls under <https://en.wikipedia.org/wiki/Primitive_recursive_function>
+
 ### FPTAS
 
 1/0 knapsack can be solved in polynomial time in $n$ and $\epsilon$ if solutions that are $1 - \epsion$ of the optimum are acceptable.
@@ -67,7 +71,7 @@ It is cool to understand how the following calculations can be implemented:
 
     Specially interesting to look at efficient different implementations and their efficienty:
 
-    - simple recursive:               $O(2^n)$ time!
+    - simple recursive: $O(2^n)$ time!
 
     - dynamic programming with array: $O(n)$ time, $O(n)$ memory.
 
 
@@ -0,0 +1,9 @@
+# data-gen
+
+Executables in this directory generate test data to an output file.
+
+The interface of each script is:
+
+    ./script <output-file> [<parameters>...]
+
+where `<parameters>` are parameters for the output generation, and depend on the exact script to be run.
@@ -0,0 +1,22 @@
+#!/usr/bin/env python
+
+"""
+Generate an uniformly distributed array of integers.
+"""
+
+import random
+import sys
+
+output_path = sys.argv[1];
+if len(sys.argv) > 2:
+    n = int(sys.argv[2])
+else:
+    n = 1000;
+minv = -2**16
+maxv = 2**16 - 1
+
+with open(output_path, 'w') as output_file:
+    output_file.write(str(n) + '\n')
+    for i in xrange(n - 1):
+        output_file.write(str(random.randint(minv, maxv)) + ' ')
+    output_file.write(str(random.randint(minv, maxv)) + '\n')
@@ -0,0 +1,2 @@
+16
+1 2 3 4 -1 -2 -3 -4 5 6 7 8 -5 -6 -7 -8
@@ -0,0 +1 @@
+0
@@ -0,0 +1,2 @@
+3
+1 2 3
@@ -0,0 +1 @@
+6
@@ -0,0 +1,2 @@
+4
+1 -1 2 3
@@ -0,0 +1 @@
+5
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	`+16`
	`2`	`+1 2 3 4 -1 -2 -3 -4 5 6 7 8 -5 -6 -7 -8`