91 lines
2.7 KiB
Python
91 lines
2.7 KiB
Python
import pyethereum
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u = pyethereum.utils
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import time
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#These are the operations that will end up in the tape
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ops = [
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lambda x, y: x+y % 2**256,
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lambda x, y: x*y % 2**256,
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lambda x, y: x % y if y > 0 else x+y,
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lambda x, y: x & y,
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lambda x, y: x | y,
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lambda x, y: x ^ y
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]
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'''
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the tape will be 'w' wide and 'd' operations deep
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it is a list of triples [i, j, op], later used
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in the tape's execution: xi = xi op xj
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'''
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def gen_tape(seed, w, d):
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tape = []
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h = 0
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#Getting as much entropy out of a hash as possible
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for i in range(d):
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if h < 2**32:
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h = u.big_endian_to_int(u.sha3(seed+str(i)))
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v1 = h % w
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h /= w
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v2 = h % w
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h /= w
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op = ops[h % len(ops)]
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h /= len(ops)
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tape.append([v1, v2, op])
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return tape
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def lshift(n):
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return 2**255 * (n % 2) + (n / 2)
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#Generates the inputs to and evaluates the tape, the mining nonce can be taken to be in the seed
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def gen_inputs(seed,w):
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#generating the tape's inputs
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v = []
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h = 0
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for i in range(w):
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if i % 1 == 0:
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h = u.big_endian_to_int(u.sha3(seed+str(i)))
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else:
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h = lshift(h)
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v.append(h)
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return v
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#Evaluate tape on inputs (incorrect dimension of v is an unhandled exception)
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def run_tape(v, tape):
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for t in tape:
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v[t[0]] = t[2](v[t[0]], v[t[1]])
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#Implemented in a blockchain, any additional hashes or timestamp would be added in the sha
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return str(v)
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# This times the various parts of the hashing function - make the tape longer to make tape evaluation dominate
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def test(num_iterations, num_tape_evals, tape_w = 100, tape_d = 1000):
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time_generating_tape = 0.
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time_generating_inputs = 0.
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time_evaluating_tape = 0.
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time_sha_capping = 0.
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for i in range(num_iterations):
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t = time.time()
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tape = gen_tape(str(i), tape_w, tape_d)
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time_generating_tape += time.time() - t
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for j in xrange(num_tape_evals):
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t = time.time()
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v = gen_inputs(str(j), tape_w)
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time_generating_inputs += time.time() - t
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t = time.time()
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x = run_tape(v,tape)
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time_evaluating_tape += time.time() - t
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t = time.time()
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h = u.sha3(x)
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time_sha_capping += time.time() - t
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total_time = time_generating_tape + time_generating_inputs + time_evaluating_tape + time_sha_capping
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print "% of time generating tape:", time_generating_tape/total_time
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print "% of time generating inputs:", time_generating_inputs/total_time
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print "% of time evaluating tape:", time_evaluating_tape/total_time
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print "% of time sha-capping:", time_sha_capping/total_time
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