Process jan's comments on the State sectionProcess jan's comments on the State sectio...

diff --git a/cλash.lhs b/cλash.lhs
index 998e6a6896adbfb0fe7381a1ea3cc0271250bfcd..dfd0a4fdc5f58595fdb890890dca5f30a112a102 100644 (file)
--- a/cλash.lhs
+++ b/cλash.lhs
@@ -974,7 +974,7 @@ circuit~\cite{reductioncircuit} for floating point numbers.
     % \comment{TODO: Describe ALU example (no code)}
 
   \subsection{State}
-    A very important concept in hardware it the concept of state. In a 
+    A very important concept in hardware is the concept of state. In a 
     stateful design, the outputs depend on the history of the inputs, or the 
     state. State is usually stored in registers, which retain their value 
     during a clock cycle. As we want to describe more than simple 
@@ -992,26 +992,24 @@ circuit~\cite{reductioncircuit} for floating point numbers.
     % This purity property is important for functional languages, since it 
     % enables all kinds of mathematical reasoning that could not be guaranteed 
     % correct for impure functions. 
-    Pure functions are as such a perfect match or a combinatorial circuit, 
-    where the output solely depends on the  inputs. When a circuit has state 
+    Pure functions are as such a perfect match for combinatorial circuits, 
+    where the output solely depends on the inputs. When a circuit has state 
     however, it can no longer be simply described by a pure function. 
     % Simply removing the purity property is not a valid option, as the 
     % language would then lose many of it mathematical properties. 
-    In an effort to include the concept of state in pure 
-    functions, the current value of the state is made an argument of the  
-    function; the updated state becomes part of the result. In this sense the
-    descriptions made in \CLaSH are the describing the combinatorial parts of 
-    a mealy machine.
+    In \CLaSH\ we deal with the concept of state in pure functions by making 
+    current value of the state an additional argument of the function and the 
+    updated state part of result. In this sense the descriptions made in 
+    \CLaSH\ are the combinatorial parts of a mealy machine.
     
     A simple example is adding an accumulator register to the earlier 
     multiply-accumulate circuit, of which the resulting netlist can be seen in 
     \Cref{img:mac-state}:
     
     \begin{code}
-    macS (State c) a b = (State c', outp)
+    macS (State c) a b = (State c', c')
       where
-        outp  = mac a b c
-        c'    = outp
+        c' = mac a b c
     \end{code}
     
     \begin{figure}
@@ -1022,7 +1020,7 @@ circuit~\cite{reductioncircuit} for floating point numbers.
     
     The \hs{State} keyword indicates which arguments are part of the current 
     state, and what part of the output is part of the updated state. This 
-    aspect will also reflected in the type signature of the function. 
+    aspect will also be reflected in the type signature of the function. 
     Abstracting the state of a circuit in this way makes it very explicit: 
     which variables are part of the state is completely determined by the 
     type signature. This approach to state is well suited to be used in 
@@ -1031,18 +1029,28 @@ circuit~\cite{reductioncircuit} for floating point numbers.
     stateful descriptions using the recursive \hs{run} function:
     
     \begin{code}
-    run f s (i:inps) = o : (run f s' inps)
+    run f s (i : inps) = o : (run f s' inps)
       where
         (s', o) = f s i
     \end{code}
     
-    The \hs{run} function maps a list of inputs over the function that a 
-    developer wants to simulate, passing the state to each new iteration. Each
-    value in the input list corresponds to exactly one cycle of the (implicit) 
-    clock. The result of the simulation is a list of outputs for every clock
-    cycle. As both the \hs{run} function and the hardware description are 
-    plain Haskell, the complete simulation can be compiled by an optimizing
-    Haskell compiler.
+    The \hs{(:)} operator is the list concatenation operator, where the 
+    left-hand side is the head of a list and the right-hand side is the 
+    remainder of the list. The \hs{run} function applies the function the 
+    developer wants to simulate, \hs{f}, to the current state, \hs{s}, and the 
+    first input value, \hs{i}. The result is the first output value, \hs{o}, 
+    and the updated state \hs{s'}. The next iteration of the \hs{run} function 
+    is then called with the updated state, \hs{s'}, and the rest of the 
+    inputs, \hs{inps}. Each value in the input list corresponds to exactly one 
+    cycle of the (implicit) clock.
+    
+    As both the \hs{run} function, the hardware description, and the test 
+    inputs are plain Haskell, the complete simulation can be compiled to an 
+    executable binary by an optimizing Haskell compiler, or executed in an 
+    Haskell interpreter. Both simulation paths are much faster than first 
+    translating the description to \VHDL\ and then running a \VHDL\ 
+    simulation, where the executable binary has an additional simulation speed 
+    bonus in case there is a large set of test inputs.
     
 \section{\CLaSH\ prototype}
 

diff --git a/mac-state.svg b/mac-state.svg
index 8f40046025f938b074f35b2f09e3920765422330..6609dfbb5f594a9160143d3913e9ecf8ae0f805e 100644 (file)
--- a/mac-state.svg
+++ b/mac-state.svg
@@ -273,5 +273,47 @@
    id="path3994"
    d="m 242.13,661.29 -0.01,-0.02 -0.02,-0.01 -0.01,-0.02 -0.02,-0.01 -0.01,-0.02 -0.01,-0.02 -0.01,-0.01 -0.02,-0.02 -0.01,-0.02 0,-0.01 -0.01,-0.02 -0.01,-0.01 -0.01,-0.02 0,-0.02 -0.01,-0.01 -0.01,-0.02 0,-0.01 0,-0.02 -0.01,-0.01 0,-0.02 -0.01,-0.01 0,-0.02 0,-0.01 0,-0.01 0,-0.02 0,-0.01 -0.01,-0.01 0,-0.01 0,-0.01 0,-0.01 0,-0.01 0,-0.01 c 0,-0.44 0.35,-0.63 0.62,-0.63 0.31,0 0.63,0.21 0.63,0.63 0,0.86 -1.16,0.92 -1.74,0.92 -1.78,0 -2.52,-1.15 -2.52,-2.31 0,-1.32 0.94,-2.27 2.47,-2.27 1.62,0 1.92,1.16 1.92,1.23 0,0.14 -0.14,0.14 -0.24,0.14 -0.18,0 -0.19,-0.02 -0.24,-0.15 -0.26,-0.63 -0.74,-0.82 -1.25,-0.82 -1.38,0 -1.38,1.47 -1.38,1.92 0,0.56 0,1.86 1.28,1.86 0.35,0 0.52,-0.03 0.65,-0.06 z"
    style="fill:#000000;stroke-width:0" />
+</g>    <g
+       id="g3387"
+       transform="matrix(1,0,0,-1,213.25,1264.2792)"
+       xml:space="preserve"
+       stroke-miterlimit="10.433"
+       font-style="normal"
+       font-variant="normal"
+       font-weight="normal"
+       font-stretch="normal"
+       font-size-adjust="none"
+       letter-spacing="normal"
+       word-spacing="normal"
+       ns0:text="$\\mathit{c}$\n\n"
+       ns0:preamble=""
+       style="font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;letter-spacing:normal;word-spacing:normal;text-anchor:start;fill:none;stroke:#000000;stroke-linecap:butt;stroke-linejoin:miter;stroke-miterlimit:10.43299961;stroke-opacity:1;stroke-dasharray:none;stroke-dashoffset:0">
+<path
+   d="m 227.77,660.99 -0.03,-0.01 -0.02,0 -0.02,0 -0.02,-0.01 -0.02,0 -0.02,-0.01 -0.02,0 -0.02,-0.01 -0.02,-0.01 -0.01,0 -0.02,-0.01 -0.01,-0.01 -0.02,-0.01 -0.01,0 -0.02,-0.01 -0.01,-0.01 -0.01,-0.01 -0.02,-0.01 -0.01,-0.01 -0.01,-0.01 -0.01,-0.01 -0.01,-0.01 -0.02,-0.02 -0.02,-0.02 -0.01,-0.02 -0.02,-0.02 -0.01,-0.02 -0.01,-0.02 -0.01,-0.02 -0.01,-0.02 -0.01,-0.02 0,-0.02 -0.01,-0.02 0,-0.02 0,-0.01 -0.01,-0.02 0,-0.01 0,-0.01 0,-0.02 0,0 0,-0.01 0,0 0,-0.01 0,0 0,0 c 0,-0.16 0.11,-0.32 0.34,-0.32 0.27,0 0.51,0.22 0.51,0.6 0,0.49 -0.43,0.86 -1.07,0.86 -1.24,0 -2.52,-1.42 -2.52,-2.87 0,-0.99 0.59,-1.65 1.46,-1.65 1.28,0 2.11,1 2.11,1.15 0,0.05 -0.09,0.16 -0.16,0.16 -0.04,0 -0.05,-0.01 -0.13,-0.11 -0.74,-0.94 -1.63,-0.98 -1.8,-0.98 -0.53,0 -0.78,0.45 -0.78,1.03 0,0.53 0.26,1.57 0.52,2.05 0.36,0.65 0.86,1 1.31,1 0.11,0 0.56,-0.02 0.71,-0.43 z"
+   id="path3389"
+   style="fill:#000000;stroke-width:0" />
+</g>    <g
+       style="font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;letter-spacing:normal;word-spacing:normal;text-anchor:start;fill:none;stroke:#000000;stroke-linecap:butt;stroke-linejoin:miter;stroke-miterlimit:10.43299961;stroke-opacity:1;stroke-dasharray:none;stroke-dashoffset:0"
+       ns0:preamble=""
+       ns0:text="$\\mathit{c\'}$\n\n\n"
+       word-spacing="normal"
+       letter-spacing="normal"
+       font-size-adjust="none"
+       font-stretch="normal"
+       font-weight="normal"
+       font-variant="normal"
+       font-style="normal"
+       stroke-miterlimit="10.433"
+       xml:space="preserve"
+       transform="matrix(1,0,0,-1,261.73,1253.7692)"
+       id="g3471">
+<path
+   id="path3473"
+   d="m 227.77,660.99 -0.03,-0.01 -0.02,0 -0.02,0 -0.02,-0.01 -0.02,0 -0.02,-0.01 -0.02,0 -0.02,-0.01 -0.02,-0.01 -0.01,0 -0.02,-0.01 -0.01,-0.01 -0.02,-0.01 -0.01,0 -0.02,-0.01 -0.01,-0.01 -0.01,-0.01 -0.02,-0.01 -0.01,-0.01 -0.01,-0.01 -0.01,-0.01 -0.01,-0.01 -0.02,-0.02 -0.02,-0.02 -0.01,-0.02 -0.02,-0.02 -0.01,-0.02 -0.01,-0.02 -0.01,-0.02 -0.01,-0.02 -0.01,-0.02 0,-0.02 -0.01,-0.02 0,-0.02 0,-0.01 -0.01,-0.02 0,-0.01 0,-0.01 0,-0.02 0,0 0,-0.01 0,0 0,-0.01 0,0 0,0 c 0,-0.16 0.11,-0.32 0.34,-0.32 0.27,0 0.51,0.22 0.51,0.6 0,0.49 -0.43,0.86 -1.07,0.86 -1.24,0 -2.52,-1.42 -2.52,-2.87 0,-0.99 0.59,-1.65 1.46,-1.65 1.28,0 2.11,1 2.11,1.15 0,0.05 -0.09,0.16 -0.16,0.16 -0.04,0 -0.05,-0.01 -0.13,-0.11 -0.74,-0.94 -1.63,-0.98 -1.8,-0.98 -0.53,0 -0.78,0.45 -0.78,1.03 0,0.53 0.26,1.57 0.52,2.05 0.36,0.65 0.86,1 1.31,1 0.11,0 0.56,-0.02 0.71,-0.43 z"
+   style="fill:#000000;stroke-width:0" />
+<path
+   id="path3475"
+   d="m 230.6,664.14 0.01,0.01 0,0.01 0,0.01 0.01,0.01 0,0.01 0.01,0.01 0,0.01 0,0.01 0.01,0.01 0,0 0,0.01 0,0.01 0.01,0.01 0,0 0,0.01 0,0.01 0,0 0.01,0.01 0,0.01 0,0 0,0.01 0,0 0,0.01 0,0 0,0.01 0,0.01 0,0.01 0,0.01 c 0,0.22 -0.19,0.39 -0.41,0.39 -0.26,0 -0.35,-0.22 -0.38,-0.33 l -0.92,-3.02 c -0.01,-0.01 -0.04,-0.11 -0.04,-0.11 0,-0.09 0.22,-0.16 0.27,-0.16 0.05,0 0.06,0.02 0.11,0.12 z"
+   style="fill:#000000;stroke-width:0" />
 </g>  </g>
 </svg>