new versions

lectures/e1.org

@@ -9,6 +9,101 @@ affiliation: KTH, Whoomph Software AB
 process: orgmode_plugin_slides
 #+END_kv
 
+* Fib
+Fibonacci numbers are defined like this:
+#+BEGIN_erlang
+-module(para1).
+...
+fib(0) -> 0;
+fib(1) -> 1;
+fib(N) -> fib(N-1) + fib(N-2). 
+#+END_erlang
+
+And run like this:
+
+#+BEGIN_shell
+$ erl
+Erlang/OTP 18 [erts-7.1] [source] ...
+Eshell V7.1  (abort with ^G)
+1> c(para1).
+{ok,par1}
+2> para1:fib(10).
+55
+#+END_shell
+
+* Testing Fib
+
+We need an {\sl independent} oracle.
+
+#+BEGIN_image
+height:4cm
+image:../lectures/fib.png
+title: Fibonacci Numbers (Wiki)
+#+END_image
+
+#+BEGIN_erlang
+test_fib() ->
+    0 = fib(0),
+    1 = fib(1),
+    144 = fib(12),
+    6765 = fib(20),
+    yes
+#+END_erlang
+
+#+BEGIN_shell
+3> para1:test_fib()
+yes
+#+END_shell
+
+* Parallel Fib
+
+#+BEGIN_erlang
+start() ->
+    start_process(1, 42),
+    start_process(2, 38),
+    start_process(3, 20),
+    start_process(4, 15),
+    start_process(5, 38),
+    start_process(6, 22),
+    wait_replies(6).
+#+END_erlang
+
+#+BEGIN_shell
+> par1:start().  
+at {10,46,50} received {process,4,fib,15,is,610}
+at {10,46,50} received {process,3,fib,20,is,6765}
+at {10,46,50} received {process,6,fib,22,is,17711}
+at {10,46,53} received {process,5,fib,38,is,39088169}
+at {10,46,53} received {process,2,fib,38,is,39088169}
+at {10,47,7}  received {process,1,fib,42,is,267914296}
+ok
+#+END_shell
+
+* The parallelisation code
+
+We use three primitive \verb+spawn+, \verb+send+ (written ``!'') and
+\verb+receive+
+to make a concurrent (and possibly parallel) program {\sl Tip: watch the
+CPU meter when running to see if it's parallel}
+
+
+#+BEGIN_erlang
+start_process(K, X) ->
+    S = self(),
+    spawn(fun() -> compute_then_reply(K, S, X) end).
+
+compute_then_reply(K, Parent, X) ->
+    Y = fib(X),
+    Parent ! {process,K,fib,X,is,Y}.
+
+wait_replies(0) ->  ok;
+wait_replies(N)  ->
+    receive
+	Any ->
+	    io:format("at ~p received ~p~n",[erlang:time(), Any]),
+	    wait_replies(N-1)
+    end.
+#+END_erlang
 * About
 
 ** Assignments and other material are at \url{https://github.com/joearms/paradis_jan_2016}.
@@ -117,26 +212,7 @@ a
 #+END_shell
 
 * e1.erl
-#+BEGIN_erlang
-tests() ->
-    1000 = fac(1000) div fac(999),
-    20 = demo1(),
-    20 = double(10),
-    36 = area({square,6}),
-    60 = perimeter({rectangle,10,20}),
-    200 = area1({rectangle,10,20}),
-    Pid1 = spawn(fun() -> area_actor() end),
-    Pid1 ! {rectangle, 10, 20},
-    Pid2 = spawn(fun() -> area_server() end),
-    200 = rpc(Pid2, {rectangle,10,20}),
-    Pid3 = spawn(fun() -> universal() end),
-    Cubed = fun(X) -> X*X*X end,
-    Pid3 ! {become, Cubed},
-    8 = rpc(Pid3, 2),
-    K1 = sum_squares_fast(1000),
-    K1 = sum_squares_slow(1000),
-    ok.
-#+END_erlang
+
 * fac
 This file is \verb+e1.erl+
 #+BEGIN_erlang

lectures/e2.org

@@ -83,7 +83,7 @@ $erl
 
 * Variables don't vary
 
-** \textcolor{Red}{Variable start with an uppercase letter} and are bound with =:
+** \textcolor{Red}{Variables start with an uppercase letter} and are bound with =:
 
 #+BEGIN_shell
 $erl
@@ -92,14 +92,15 @@ $erl
 10
 2> X = 20.
   exception error: 
-   no match of right hand side value 20
+  no match of right hand side value 20
 ...
 3> X1 = 20.
 20
 #+END_shell
 
 ** Use a new variable each time (more later)
 
+
 * Data Types
 Erlang has two types of data.
 There are {\sl Primitive data types} (atoms, integers, floats) etc. and
@@ -121,14 +122,29 @@ abc
 
 * Strings
 ** There are no strings in Erlang.
-** Strings are lists of integers:
+** Strings literals in programs are syntactic sugar (ie a different way of writing) for lists of integers:
+
 #+BEGIN_shell
 1> "abc".
 "abc".
 2> [abc|"abc"].
 [abc,97,98,99]
 #+END_shell
 
+
+* Strings (aside)
+
+** Strings are abstract data types which manipulate sequences of characters.
+** Characters are NOT bytes.
+** Files contain bytes.
+** The textual representation of programs contain string literals.
+** Character handling and string representation is a total mess in all programming languages and OS's.
+
+Stick to \verb+latin1+, \verb+ASCII+, \verb+Unicode+ and \verb+UTF8+
+and don't mix them.
+
+If you really want to know read the Unicode standard.
+
 * Primitive Data Types
 
 ** Atoms \verb+monday+ \verb+tuesday+ - \textcolor{Red}{Remember atoms start with a lower case letters}.

lectures/para1.erl

@@ -0,0 +1,45 @@
+-module(para1).
+
+-export([start/0, fib/1, test_fib/0]).
+
+start() ->
+    start_process(1, 42),
+    start_process(2, 38),
+    start_process(3, 20),
+    start_process(4, 15),
+    start_process(5, 38),
+    start_process(6, 22),
+    wait_replies(6).
+
+wait_replies(0) ->  ok;
+wait_replies(N)  ->
+    receive
+	Any ->
+	    io:format("at ~p received ~p~n",[erlang:time(), Any]),
+	    wait_replies(N-1)
+    end.
+
+start_process(K, X) ->
+    S = self(),
+    spawn(fun() -> compute_then_reply(K, S, X) end).
+
+compute_then_reply(K, Parent, X) ->
+    Y = fib(X),
+    Parent ! {process,K,fib,X,is,Y}.
+
+test_fib() ->
+    0 = fib(0),
+    1 = fib(1),
+    144 = fib(12),
+    6765 = fib(20),
+    yes.
+
+fib(0) -> 0;
+fib(1) -> 1;
+fib(N) -> fib(N-1) + fib(N-2). 
+
+
+
+
+
+

lectures/problems_1.tex

@@ -1,7 +1,7 @@
 \documentclass[12pt]{hitec}
 
 \usepackage{fancyvrb}
-%% \usepackage{hyperref}
+\usepackage{hyperref}
 
 \title{Problem set 1}
 \author{Joe Armstrong}
@@ -23,7 +23,10 @@ \section{Problems}
 The first exercises involve correcting
 incorrect programs. The program \verb+bad_prog1.erl+ in my github repository
 \newline
-\verb+http://joearms.github.com/paradis_2016/src/bad_prog1.erl+ has a
+\href{https://github.com/joearms/paradis\_jan\_2016/blob/master/lectures/bad\_prog1.erl}
+     {https://github.com/joearms/paradis\_jan\_2016/}
+
+has a 
 large number of errors.
 
 \VerbatimInput[frame=single]{./bad_prog1.erl}
@@ -52,7 +55,7 @@ \section{Problems}
 
 \section{A bank account}
 
-The follow program implements a simple bank process, where the code
+The following program implements a simple bank process, where the code
 you have to write has been replaced by the atom \verb+implement_this+.
 
 Replace the \verb+implement_this+ atoms by correct code. 
@@ -117,5 +120,14 @@ \section{Unit Tests}
 of \verb+F(X)+ converting them to error tuples of the form \verb+{'EXIT', Why}+
 which we match with the pattern \verb+{'EXIT', _}+.
 
+\section*{Notes}
+
+\href{https://github.com/joearms/paradis\_jan\_2016/blob/master/lectures/}
+     {https://github.com/joearms/paradis\_jan\_2016/blob/master/lectures/}
+     contains material referred to in the problems.
+
+If you want to build the lectures locally you will need a working verison
+of erlang and pdflatex installed on your machine.
+
 \end{document}