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https://github.com/tahoe-lafs/tahoe-lafs.git
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4b4f5bbcba
Note that using "whatever version of python the name 'python' maps to in the current shell environment" is more error-prone that specifying which python you mean, such as by executing "/usr/bin/python setup.py" instead of executing "./setup.py". When you build tahoe (by running "make") it will make a copy of bin/allmydata-tahoe in instdir/bin/allmydata-tahoe with the shebang line rewritten to execute the specific version of python that was used when building instead of to execute "/usr/bin/env python". However, it seems better that the default for lazy people be "whatever 'python' means currently" instead of "whatever 'python' meant to the manufacturer of your operating system".
214 lines
7.8 KiB
Python
214 lines
7.8 KiB
Python
#! /usr/bin/env python
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import random, math, os, re
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from twisted.python import usage
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class Args(usage.Options):
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optParameters = [
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["mode", "m", "alpha", "validation scheme"],
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["arity", "k", 2, "k (airty) for hash tree"],
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]
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def opt_arity(self, option):
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self['arity'] = int(option)
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def parseArgs(self, *args):
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if len(args) > 0:
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self['mode'] = args[0]
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def charttest():
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import gdchart
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sizes = [random.randrange(10, 20) for i in range(10)]
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x = gdchart.Line()
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x.width = 250
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x.height = 250
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x.xtitle = "sample"
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x.ytitle = "size"
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x.title = "Example Graph"
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#x.ext_color = [ "white", "yellow", "red", "blue", "green"]
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x.setData(sizes)
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#x.setLabels(["Mon", "Tue", "Wed", "Thu", "Fri"])
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x.draw("simple.png")
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KiB=1024
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MiB=1024*KiB
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GiB=1024*MiB
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TiB=1024*GiB
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PiB=1024*TiB
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class Sizes:
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def __init__(self, mode, file_size, arity=2):
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MAX_SEGSIZE = 2*MiB
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self.mode = mode
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self.file_size = file_size
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self.seg_size = seg_size = 1.0 * min(MAX_SEGSIZE, file_size)
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self.num_segs = num_segs = math.ceil(file_size / seg_size)
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self.num_subblocks = num_subblocks = num_segs
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self.num_blocks = num_blocks = 100
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self.blocks_needed = blocks_needed = 25
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self.subblock_size = subblock_size = seg_size / blocks_needed
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self.block_size = block_size = subblock_size * num_subblocks
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# none of this includes the block-level hash chain yet, since that is
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# only a function of the number of blocks. All overhead numbers
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# assume that the block-level hash chain has already been sent,
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# including the root of the subblock-level hash tree.
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if mode == "alpha":
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# no hash tree at all
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self.subblock_arity = 0
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self.subblock_tree_depth = 0
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self.subblock_overhead = 0
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self.bytes_until_some_data = 20 + block_size
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self.block_storage_overhead = 0
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self.block_transmission_overhead = 0
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elif mode == "beta":
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# k=num_subblocks, d=1
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# each subblock has a 20-byte hash
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self.subblock_arity = num_subblocks
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self.subblock_tree_depth = 1
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self.subblock_overhead = 20
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# the block has a list of hashes, one for each subblock
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self.block_storage_overhead = (self.subblock_overhead *
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num_subblocks)
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# we can get away with not sending the hash of the block that
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# we're sending in full, once
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self.block_transmission_overhead = self.block_storage_overhead - 20
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# we must get the whole list (so it can be validated) before
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# any data can be validated
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self.bytes_until_some_data = (self.block_transmission_overhead +
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subblock_size)
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elif mode == "gamma":
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self.subblock_arity = k = arity
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d = math.ceil(math.log(num_subblocks, k))
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self.subblock_tree_depth = d
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num_leaves = k ** d
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# to make things easier, we make the pessimistic assumption that
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# we have to store hashes for all the empty places in the tree
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# (when the number of blocks is not an exact exponent of k)
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self.subblock_overhead = 20
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# the subblock hashes are organized into a k-ary tree, which
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# means storing (and eventually transmitting) more hashes. This
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# count includes all the low-level block hashes and the root.
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hash_nodes = (num_leaves*k - 1) / (k - 1)
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#print "hash_depth", d
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#print "num_leaves", num_leaves
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#print "hash_nodes", hash_nodes
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# the storage overhead is this
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self.block_storage_overhead = 20 * (hash_nodes - 1)
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# the transmission overhead is smaller: if we actually transmit
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# every subblock, we don't have to transmit 1/k of the
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# lowest-level subblock hashes, and we don't have to transmit the
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# root because it was already sent with the block-level hash tree
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self.block_transmission_overhead = 20 * (hash_nodes
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- 1 # the root
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- num_leaves / k)
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# we must get a full sibling hash chain before we can validate
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# any data
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sibling_length = d * (k-1)
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self.bytes_until_some_data = 20 * sibling_length + subblock_size
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else:
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raise RuntimeError("unknown mode '%s" % mode)
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self.storage_overhead = self.block_storage_overhead * num_blocks
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self.storage_overhead_percentage = 100.0 * self.storage_overhead / file_size
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def dump(self):
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for k in ("mode", "file_size", "seg_size",
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"num_segs", "num_subblocks", "num_blocks", "blocks_needed",
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"subblock_size", "block_size",
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"subblock_arity", "subblock_tree_depth",
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"subblock_overhead",
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"block_storage_overhead", "block_transmission_overhead",
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"storage_overhead", "storage_overhead_percentage",
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"bytes_until_some_data"):
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print k, getattr(self, k)
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def fmt(num, trim=False):
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if num < KiB:
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#s = str(num) + "#"
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s = "%.2f#" % num
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elif num < MiB:
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s = "%.2fk" % (num / KiB)
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elif num < GiB:
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s = "%.2fM" % (num / MiB)
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elif num < TiB:
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s = "%.2fG" % (num / GiB)
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elif num < PiB:
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s = "%.2fT" % (num / TiB)
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else:
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s = "big"
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if trim:
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s = re.sub(r'(\.0+)([kMGT#])',
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lambda m: m.group(2),
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s)
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else:
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s = re.sub(r'(\.0+)([kMGT#])',
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lambda m: (" "*len(m.group(1))+m.group(2)),
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s)
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if s.endswith("#"):
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s = s[:-1] + " "
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return s
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def text():
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opts = Args()
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opts.parseOptions()
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mode = opts["mode"]
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arity = opts["arity"]
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# 0123456789012345678901234567890123456789012345678901234567890123456
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print "mode=%s" % mode, " arity=%d" % arity
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print " storage storage"
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print "Size blocksize overhead overhead k d alacrity"
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print " (bytes) (%)"
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print "------- ------- -------- -------- ---- -- --------"
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#sizes = [2 ** i for i in range(7, 41)]
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radix = math.sqrt(10); expstep = 2
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radix = 2; expstep = 2
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#radix = 10; expstep = 1
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maxexp = int(math.ceil(math.log(1e12, radix)))+2
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sizes = [radix ** i for i in range(2,maxexp,expstep)]
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for file_size in sizes:
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s = Sizes(mode, file_size, arity)
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out = ""
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out += "%7s " % fmt(file_size, trim=True)
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out += "%7s " % fmt(s.block_size)
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out += "%8s" % fmt(s.storage_overhead)
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out += "%10.2f " % s.storage_overhead_percentage
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out += " %4d" % int(s.subblock_arity)
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out += " %2d" % int(s.subblock_tree_depth)
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out += " %8s" % fmt(s.bytes_until_some_data)
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print out
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def graph():
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# doesn't work yet
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import Gnuplot
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opts = Args()
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opts.parseOptions()
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mode = opts["mode"]
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arity = opts["arity"]
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g = Gnuplot.Gnuplot(debug=1)
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g.title("overhead / alacrity tradeoffs")
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g.xlabel("file size")
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g.ylabel("stuff")
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sizes = [2 ** i for i in range(7, 32)]
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series = {"overhead": {}, "alacrity": {}}
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for file_size in sizes:
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s = Sizes(mode, file_size, arity)
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series["overhead"][file_size] = s.storage_overhead_percentage
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series["alacrity"][file_size] = s.bytes_until_some_data
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g.plot([ (fs, series["overhead"][fs])
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for fs in sizes ])
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raw_input("press return")
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if __name__ == '__main__':
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text()
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#graph()
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