My Advent of Code solutions in Python.
kevinyap.ca/2019/12/going-fast-in-advent-of-code/
advent-of-code
python
Update 2017/23 solution
Use peephole optimizations to solve Part 2 via emulation.
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2017/day23.py
+63
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2017/day23.py
···
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import fileinput
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from collections import defaultdict
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from utils import parse_line, mul, all_unique, factors, memoize, primes # NOQA
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def emulate(instrs, **reg_init):
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regs = defaultdict(int)
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for k, v in reg_init.items():
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regs[k] = v
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INSTRS = []
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B = None
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pc = 0
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while 0 <= pc < len(instrs):
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op, x, y = instrs[pc]
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y = regs[y] if y.isalpha() else int(y)
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if op == 'set':
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regs[x] = y
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elif op == 'sub':
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regs[x] -= y
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elif op == 'mul':
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regs[x] *= y
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regs['_muls'] += 1
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elif op == 'mod':
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regs[x] %= y
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elif op == 'sqrt':
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regs[x] = int(math.sqrt(y)) + 1
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elif op == 'jnz':
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if (regs[x] if x.isalpha() else int(x)) != 0:
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pc += y
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continue
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pc += 1
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return regs
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# Read puzzle input
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INSTRS = []
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for line in fileinput.input():
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instr = line.strip() + ' foo'
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op, x, y = instr.split()[:3]
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INSTRS.append((op, x, y))
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if fileinput.isfirstline():
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B = int(y)
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# Part 1
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REGS = defaultdict(int)
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pc = 0
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muls = 0
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print "`mul` instruction invocations:", emulate(INSTRS)['_muls']
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while 0 <= pc < len(INSTRS):
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op, x, y = INSTRS[pc]
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y = REGS[y] if y.isalpha() else int(y)
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# Part 2
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#
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# Perform peephole optimizations to speed up execution of Part 2
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# (inspired by https://www.reddit.com/r/adventofcode/comments/7lrjei)
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#
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# Speed up composite check using modulo
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# set e 2 -> set g b
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# set g d -> mod g d
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# mul g e -> jnz g 8
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# sub g b -> set f 0
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# jnz g 2 -> jnz 1 11
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# set f 0 -> nop
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# sub e -1 -> nop
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# set g e -> nop
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# sub g b -> nop
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# jnz g -8 -> nop
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#
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# Only check integers up to sqrt(n)
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# set g d -> sqrt g b
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# sub g b -> sub g d
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if op == 'set':
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REGS[x] = y
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elif op == 'sub':
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REGS[x] -= y
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elif op == 'mul':
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REGS[x] *= y
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muls += 1
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elif op == 'mod':
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REGS[x] %= y
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elif op == 'jnz':
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if (REGS[x] if x.isalpha() else int(x)) != 0:
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pc += y
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continue
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INSTRS[10] = ['set', 'g', 'b']
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INSTRS[11] = ['mod', 'g', 'd']
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INSTRS[12] = ['jnz', 'g', '8']
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INSTRS[13] = ['set', 'f', '0']
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INSTRS[14] = ['jnz', '1', '11']
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pc += 1
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print "`mul` instruction invocations:", muls
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INSTRS[21] = ['sqrt', 'g', 'b']
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INSTRS[22] = ['sub', 'g', 'd']
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# Part 2
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b = (B * 100) + 100000
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c = b + 17000
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h = 0
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for n in range(b, c + 1, 17):
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for i in range(2, int(math.sqrt(n))):
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if n % i == 0:
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h += 1
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break
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print "Value in register h, ie. primes in [{}, {}]: {}".format(b, c, h)
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print "Value in register h:", emulate(INSTRS, a=1)['h']