|
1 // Part 2 about a "Compiler" for the Brainf*** language |
|
2 //====================================================== |
|
3 |
|
4 object CW10b { |
|
5 |
|
6 // !!! Copy any function you need from file bf.scala !!! |
|
7 // |
|
8 // If you need any auxiliary function, feel free to |
|
9 // implement it, but do not make any changes to the |
|
10 // templates below. |
|
11 |
|
12 |
|
13 def time_needed[T](n: Int, code: => T) = { |
|
14 val start = System.nanoTime() |
|
15 for (i <- 0 until n) code |
|
16 val end = System.nanoTime() |
|
17 (end - start)/(n * 1.0e9) |
|
18 } |
|
19 |
|
20 type Mem = Map[Int, Int] |
|
21 |
|
22 |
|
23 import io.Source |
|
24 import scala.util._ |
|
25 |
|
26 def load_bff(name: String) : String = |
|
27 Try(Source.fromFile(name)("ISO-8859-1").mkString).getOrElse("") |
|
28 |
|
29 def sread(mem: Mem, mp: Int) : Int = |
|
30 mem.getOrElse(mp, 0) |
|
31 |
|
32 def write(mem: Mem, mp: Int, v: Int) : Mem = |
|
33 mem.updated(mp, v) |
|
34 |
|
35 def jumpRight(prog: String, pc: Int, level: Int) : Int = { |
|
36 if (prog.length <= pc) pc |
|
37 else (prog(pc), level) match { |
|
38 case (']', 0) => pc + 1 |
|
39 case (']', l) => jumpRight(prog, pc + 1, l - 1) |
|
40 case ('[', l) => jumpRight(prog, pc + 1, l + 1) |
|
41 case (_, l) => jumpRight(prog, pc + 1, l) |
|
42 } |
|
43 } |
|
44 |
|
45 def jumpLeft(prog: String, pc: Int, level: Int) : Int = { |
|
46 if (pc < 0) pc |
|
47 else (prog(pc), level) match { |
|
48 case ('[', 0) => pc + 1 |
|
49 case ('[', l) => jumpLeft(prog, pc - 1, l - 1) |
|
50 case (']', l) => jumpLeft(prog, pc - 1, l + 1) |
|
51 case (_, l) => jumpLeft(prog, pc - 1, l) |
|
52 } |
|
53 } |
|
54 |
|
55 def compute(prog: String, pc: Int, mp: Int, mem: Mem) : Mem = { |
|
56 if (0 <= pc && pc < prog.length) { |
|
57 val (new_pc, new_mp, new_mem) = prog(pc) match { |
|
58 case '>' => (pc + 1, mp + 1, mem) |
|
59 case '<' => (pc + 1, mp - 1, mem) |
|
60 case '+' => (pc + 1, mp, write(mem, mp, sread(mem, mp) + 1)) |
|
61 case '-' => (pc + 1, mp, write(mem, mp, sread(mem, mp) - 1)) |
|
62 case '.' => { print(sread(mem, mp).toChar); (pc + 1, mp, mem) } |
|
63 case '[' => |
|
64 if (sread(mem, mp) == 0) (jumpRight(prog, pc + 1, 0), mp, mem) else (pc + 1, mp, mem) |
|
65 case ']' => |
|
66 if (sread(mem, mp) != 0) (jumpLeft(prog, pc - 1, 0), mp, mem) else (pc + 1, mp, mem) |
|
67 case _ => (pc + 1, mp, mem) |
|
68 } |
|
69 compute(prog, new_pc, new_mp, new_mem) |
|
70 } |
|
71 else mem |
|
72 } |
|
73 |
|
74 def run(prog: String, m: Mem = Map()) = compute(prog, 0, 0, m) |
|
75 |
|
76 |
|
77 // The baseline to what we can compare our "compiler" |
|
78 // implemented below. It should require something like |
|
79 // 60 seconds for the calculation on my laptop |
|
80 // |
|
81 //time_needed(1, run(load_bff("benchmark.bf"))) |
|
82 |
|
83 |
|
84 |
|
85 // DEBUGGING INFORMATION!!! |
|
86 // |
|
87 // Compiler, even real ones, are fiedishly difficult to get |
|
88 // to prduce correct code. The point is that for example for |
|
89 // the sierpinski program, they need to still generate code |
|
90 // that displays such a triangle. If yes, then one usually |
|
91 // can take comfort that all is well. If not, then something |
|
92 // went wrong during the optimisations. |
|
93 |
|
94 |
|
95 |
|
96 // (5) Write a function jtable that precomputes the "jump |
|
97 // table" for a bf-program. This function takes a bf-program |
|
98 // as an argument and Returns a Map[Int, Int]. The |
|
99 // purpose of this map is to record the information |
|
100 // that given on the position pc is a '[' or a ']', |
|
101 // then to which pc-position do we need to jump next? |
|
102 // |
|
103 // For example for the program |
|
104 // |
|
105 // "+++++[->++++++++++<]>--<+++[->>++++++++++<<]>>++<<----------[+>.>.<+<]" |
|
106 // |
|
107 // we obtain the map |
|
108 // |
|
109 // Map(69 -> 61, 5 -> 20, 60 -> 70, 27 -> 44, 43 -> 28, 19 -> 6) |
|
110 // |
|
111 // This states that for the '[' on position 5, we need to |
|
112 // jump to position 20, which is just after the corresponding ']'. |
|
113 // Similarly, for the ']' on position 19, we need to jump to |
|
114 // position 6, which is just after the '[' on position 5, and so |
|
115 // on. The idea is to not calculate this information each time |
|
116 // we hit a bracket, but just look up this information in the |
|
117 // jtable. You can use the jumpLeft and jumpRight functions |
|
118 // from Part 1 for calculating the jtable. |
|
119 // |
|
120 // Then adapt the compute and run functions from Part 1 in order |
|
121 // to take advantage of the information stored in the jtable. |
|
122 // This means whenever jumpLeft and jumpRight was called previously, |
|
123 // you should look up the jump address in the jtable. |
|
124 |
|
125 |
|
126 def jtable(pg: String) : Map[Int, Int] = |
|
127 (0 until pg.length).collect { pc => pg(pc) match { |
|
128 case '[' => (pc -> jumpRight(pg, pc + 1, 0)) |
|
129 case ']' => (pc -> jumpLeft(pg, pc - 1, 0)) |
|
130 }}.toMap |
|
131 |
|
132 |
|
133 // testcase |
|
134 // jtable("""+++++[->++++++++++<]>--<+++[->>++++++++++<<]>>++<<----------[+>.>.<+<]""") |
|
135 // => Map(69 -> 61, 5 -> 20, 60 -> 70, 27 -> 44, 43 -> 28, 19 -> 6) |
|
136 |
|
137 |
|
138 def compute2(pg: String, tb: Map[Int, Int], pc: Int, mp: Int, mem: Mem) : Mem = { |
|
139 if (0 <= pc && pc < pg.length) { |
|
140 val (new_pc, new_mp, new_mem) = pg(pc) match { |
|
141 case '>' => (pc + 1, mp + 1, mem) |
|
142 case '<' => (pc + 1, mp - 1, mem) |
|
143 case '+' => (pc + 1, mp, write(mem, mp, sread(mem, mp) + 1)) |
|
144 case '-' => (pc + 1, mp, write(mem, mp, sread(mem, mp) - 1)) |
|
145 case '.' => { print(sread(mem, mp).toChar); (pc + 1, mp, mem) } |
|
146 case '[' => |
|
147 if (sread(mem, mp) == 0) (tb(pc), mp, mem) else (pc + 1, mp, mem) |
|
148 case ']' => |
|
149 if (sread(mem, mp) != 0) (tb(pc), mp, mem) else (pc + 1, mp, mem) |
|
150 case _ => (pc + 1, mp, mem) |
|
151 } |
|
152 compute2(pg, tb, new_pc, new_mp, new_mem) |
|
153 } |
|
154 else mem |
|
155 } |
|
156 |
|
157 |
|
158 def run2(pg: String, m: Mem = Map()) = |
|
159 compute2(pg, jtable(pg), 0, 0, m) |
|
160 |
|
161 //time_needed(1, run2(load_bff("benchmark.bf"))) |
|
162 |
|
163 |
|
164 |
|
165 // (6) Write a function optimise which deletes "dead code" (everything |
|
166 // that is not a bf-command) and also replaces substrings of the form |
|
167 // [-] by a new command 0. The idea is that the loop [-] just resets the |
|
168 // memory at the current location to 0. In the compute3 and run3 functions |
|
169 // below you implement this command by writing the number 0 to mem(mp), |
|
170 // that is write(mem, mp, 0). |
|
171 // |
|
172 // The easiest way to modify a string in this way is to use the regular |
|
173 // expression """[^<>+-.\[\]@*#]""", which recognises everything that is |
|
174 // not a bf-command and replace it by the empty string. Similarly the |
|
175 // regular expression """\[-\]""" finds all occurences of [-] and |
|
176 // by using the Scala method .replaceAll you can repplace it with the |
|
177 // string "0" standing for the new bf-command. |
|
178 |
|
179 def optimise(s: String) : String = { |
|
180 s.replaceAll("""[^<>+-.\[\]@*#]""","") |
|
181 .replaceAll("""\[-\]""", "0") |
|
182 } |
|
183 |
|
184 |
|
185 def compute3(pg: String, tb: Map[Int, Int], pc: Int, mp: Int, mem: Mem) : Mem = { |
|
186 if (0 <= pc && pc < pg.length) { |
|
187 val (new_pc, new_mp, new_mem) = pg(pc) match { |
|
188 case '0' => (pc + 1, mp, write(mem, mp, 0)) |
|
189 case '>' => (pc + 1, mp + 1, mem) |
|
190 case '<' => (pc + 1, mp - 1, mem) |
|
191 case '+' => (pc + 1, mp, write(mem, mp, sread(mem, mp) + 1)) |
|
192 case '-' => (pc + 1, mp, write(mem, mp, sread(mem, mp) - 1)) |
|
193 case '.' => { print(sread(mem, mp).toChar); (pc + 1, mp, mem) } |
|
194 case '[' => |
|
195 if (sread(mem, mp) == 0) (tb(pc), mp, mem) else (pc + 1, mp, mem) |
|
196 case ']' => |
|
197 if (sread(mem, mp) != 0) (tb(pc), mp, mem) else (pc + 1, mp, mem) |
|
198 case _ => (pc + 1, mp, mem) |
|
199 } |
|
200 compute3(pg, tb, new_pc, new_mp, new_mem) |
|
201 } |
|
202 else mem |
|
203 } |
|
204 |
|
205 def run3(pg: String, m: Mem = Map()) = { |
|
206 val pg_opt = optimise(pg) |
|
207 compute3(pg_opt, jtable(pg_opt), 0, 0, m) |
|
208 } |
|
209 |
|
210 |
|
211 // testcases |
|
212 |
|
213 //println(optimise(load_bff("collatz.bf"))) |
|
214 //optimise(load_bff("benchmark.bf")) // should have inserted 0's |
|
215 //optimise(load_bff("mandelbrot.bf")).length // => 11203 |
|
216 |
|
217 //time_needed(1, run3(load_bff("benchmark.bf"))) |
|
218 |
|
219 |
|
220 |
|
221 // (7) Write a function combine which replaces sequences |
|
222 // of repated increment and decrement commands by appropriate |
|
223 // two-character commands. For example for sequences of + |
|
224 // |
|
225 // orig bf-cmds | replacement |
|
226 // ------------------------------ |
|
227 // + | +A |
|
228 // ++ | +B |
|
229 // +++ | +C |
|
230 // | |
|
231 // ... | |
|
232 // | |
|
233 // +++....+++ | +Z |
|
234 // (where length = 26) |
|
235 // |
|
236 // Similar for the bf-command -, > and <. All other commands should |
|
237 // be unaffected by this change. |
|
238 // |
|
239 // Adapt the compute4 and run4 functions such that they can deal |
|
240 // appropriately with such two-character commands. |
|
241 |
|
242 def splice(cs: List[Char], acc: List[(Char, Int)]) : List[(Char, Int)] = (cs, acc) match { |
|
243 case (Nil, acc) => acc |
|
244 case ('[' :: cs, acc) => splice(cs, ('[', 1) :: acc) |
|
245 case (']' :: cs, acc) => splice(cs, (']', 1) :: acc) |
|
246 case ('.' :: cs, acc) => splice(cs, ('.', 1) :: acc) |
|
247 case ('0' :: cs, acc) => splice(cs, ('0', 1) :: acc) |
|
248 case (c :: cs, Nil) => splice(cs, List((c, 1))) |
|
249 case (c :: cs, (d, n) :: acc) => |
|
250 if (c == d && n < 26) splice(cs, (c, n + 1) :: acc) |
|
251 else splice(cs, (c, 1) :: (d, n) :: acc) |
|
252 } |
|
253 |
|
254 def spl(s: String) = splice(s.toList, Nil).reverse |
|
255 |
|
256 //spl(load_bff("benchmark.bf")) |
|
257 |
|
258 def combine(s: String) : String = { |
|
259 (for ((c, n) <- spl(s)) yield c match { |
|
260 case '>' => List('>', (n + '@').toChar) |
|
261 case '<' => List('<', (n + '@').toChar) |
|
262 case '+' => List('+', (n + '@').toChar) |
|
263 case '-' => List('-', (n + '@').toChar) |
|
264 case _ => List(c) |
|
265 }).flatten.mkString |
|
266 } |
|
267 |
|
268 |
|
269 //combine(load_bff("benchmark.bf")) |
|
270 |
|
271 def compute4(pg: String, tb: Map[Int, Int], pc: Int, mp: Int, mem: Mem) : Mem = { |
|
272 if (0 <= pc && pc < pg.length) { |
|
273 val (new_pc, new_mp, new_mem) = pg(pc) match { |
|
274 case '0' => (pc + 1, mp, write(mem, mp, 0)) |
|
275 case '>' => (pc + 2, mp + (pg(pc + 1) - '@'), mem) |
|
276 case '<' => (pc + 2, mp - (pg(pc + 1) - '@'), mem) |
|
277 case '+' => (pc + 2, mp, write(mem, mp, sread(mem, mp) + (pg(pc + 1) - '@'))) |
|
278 case '-' => (pc + 2, mp, write(mem, mp, sread(mem, mp) - (pg(pc + 1) - '@'))) |
|
279 case '.' => { print(sread(mem, mp).toChar); (pc + 1, mp, mem) } |
|
280 case '[' => |
|
281 if (sread(mem, mp) == 0) (tb(pc), mp, mem) else (pc + 1, mp, mem) |
|
282 case ']' => |
|
283 if (sread(mem, mp) != 0) (tb(pc), mp, mem) else (pc + 1, mp, mem) |
|
284 case _ => (pc + 1, mp, mem) |
|
285 } |
|
286 compute4(pg, tb, new_pc, new_mp, new_mem) |
|
287 } |
|
288 else mem |
|
289 } |
|
290 |
|
291 def run4(pg: String, m: Mem = Map()) = { |
|
292 val pg_opt = combine(optimise(pg)) |
|
293 compute4(pg_opt, jtable(pg_opt), 0, 0, m) |
|
294 } |
|
295 |
|
296 // testcases |
|
297 //println(combine(optimise(load_bff("mandelbrot.bf").drop(123)))) |
|
298 |
|
299 //combine(optimise(load_bff("benchmark.bf"))) // => """>A+B[<A+M>A-A]<A[[.....""" |
|
300 |
|
301 //time_needed(1, run4(load_bff("benchmark.bf"))) |
|
302 |
|
303 //time_needed(1, run(load_bff("sierpinski.bf"))) |
|
304 //time_needed(1, run4(load_bff("sierpinski.bf"))) |
|
305 |
|
306 //println(time_needed(1, run4(load_bff("mandelbrot.bf")))) |
|
307 |
|
308 |
|
309 |
|
310 |
|
311 |
|
312 } |
|
313 |
|
314 /* |
|
315 import CW10b._ |
|
316 println(time_needed(1, run(load_bff("collatz.bf")))) |
|
317 println(time_needed(1, run2(load_bff("collatz.bf")))) |
|
318 println(time_needed(1, run3(load_bff("collatz.bf")))) |
|
319 println(time_needed(1, run4(load_bff("collatz.bf")))) |
|
320 */ |