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Data processing findings — Bitcoin complex-network study
Status: dataset acquired, extraction code ported and applied end-to-end to real chain data. Date: 2026-10-02
1. The paper's dataset (downloaded, verified)
Source: https://dynamics.cs.washington.edu/nobackup/bitcoin/bitcoin.tar.gz
- 678,858,686 bytes; last modified 2018-01-19; sha256
3dfda89e481ec26051a9cca819698486ae5e38236dbe7f3d21da00491eabf499 - Landing page
https://dynamics.cs.washington.edu/data.htmlis now an archival, unmaintained UW collection.
Contents: GraphLab SFrame (bitcoin.vertices.sframe/, bitcoin.links.sframe/) plus CSV exports:
bitcoin.vertices.csv—vid, first_transaction_date— 6,336,769 usersbitcoin.links.csv—dst_id, src_id, count, maxdate, mindate— 16,057,711 directed user pairs,sum(count)= 28,143,065 transactions, 5,397,167 sources / 6,229,737 destinations, 2009-01-11 → 2013-04-10, zero self-loops (src == dst count = 0)
Critical: this is an already-clustered, pair-aggregated graph. It is NOT an input to the extraction code, and the per-transaction edge list behind the paper's Table 1 is not in it. The published graph also has self-loops removed, which matters (see §4).
2. Extraction code (ported)
Original: github.com/ivanbrugere/Bitcoin-Transaction-Network-Extraction (branch master),
Python 2 (bsddb, print statements, has_key), written 2012-2013, reads a raw text dump
produced by Harrigan's bitcointools fork (dbdump.py --all-transactions).
Faithful Python 3 port in code/btc_py3/ (algorithm unchanged; only bsddb → in-memory
HashDB shim, print syntax, list semantics):
process_bitcoin_network.py, write_network_dictionaries.py, fix_missing_public_keys.py,
write_user_public_keys.py, write_user_edges.py, hashdb.py
Input format:
in <own_txid> <referent_txid> <input_index> <pubkey> <date>
out <own_txid> <output_index> <pubkey> <value_btc> <date>
Outputs: transactionkey_list.txt, pubkey_list.txt, userkey_list.txt,
user_edge_inputs.txt, user_edge_input_public_keys.txt, and the main file
user_edges.txt = [tx_id, user_from, user_to, date, value_btc].
Validated with a synthetic input exercising every path (coinbase → self-loop, change-address
self-loop, multi-input cluster merge, (None) bucket). Result matched predictions exactly.
3. Bridge from the AWS Open Data parquet
scripts/download_parquet_days.py → scripts/gen_transactions_txt.py
(public bucket s3://aws-public-blockchain/v1.0/btc/, HTTP, no credentials).
Two format traps found by inspection — both silent, neither self-announcing:
- Timestamp must be a single whitespace-free token of ≥19 chars. The parser slices fixed
character positions 0:4,5:7,8:10,11:13,14:16,17:19, so an ISO
Tseparator works and a space silently dropsHH:MM:SS(and does NOT error). - Coinbase txs must emit only their
outlines (the original dump tagged their referentcoinbaseand the parser skips those). That is the mechanism by which coinbase rewards become self-loop edges downstream.
Node identity in early data (the big one)
The ETL leaves address NULL for pay-to-pubkey scripts — i.e. essentially all early mining
rewards. In the 2010 window measured: 29.15% of outputs and 24.65% of inputs had no
address. Bucketing them as (None) would collapse a quarter of early nodes into one
pseudo-hub and destroy the graph. Recovery:
- Outputs: the pubkey is inline in
script_hex—41|21 <pubkey> ac(134 / 70 hex chars, note 65-byte uncompressed pubkeys, not 64). → 29.15% → 0.001% unresolved. - Inputs: the ETL stores only the signature in a P2PK spend's
script_hex(no pubkey, no address). Recovered by back-joining to the consumed output on(spent_transaction_hash, spent_output_index). → 24.65% → 0.000% unresolved.
Schema drift across partitions — CORRECTED, it is NOT data loss
The AWS transactions table shows three variants, interleaved day by day:
- 255 days: no
inputscolumn at all - 18 days:
inputspresent butoutputshas noaddress - 450 days: complete
Earlier I recorded that "those 255 days cannot yield edges or clustering". That was wrong. Two exhaustive tests over all 723 local 2009-2010 partitions show the drift is empty-column omission by the ETL writer, i.e. information-preserving:
Test A — inputs column present <=> the day has at least one non-coinbase transaction
inputs absent & 0 non-coinbase txs : 255 days
inputs present & >=1 non-coinbase : 468 days
Zero exceptions. And because coinbase transactions carry no inputs by construction (they are NULL even in complete partitions), a day with no non-coinbase transaction loses nothing:
- 2009 degraded days: 20,628 txs, 20,628 coinbase, 0 non-coinbase
- 2010 degraded days: 1,893 txs, 1,893 coinbase, 0 non-coinbase
- non-coinbase transactions lost across 2009-2010: 0 of 117,604 (0.00%)
Test C — outputs.address absent <=> every output on that day is P2PK
273/273 no-address days have 100% type='pubkey' outputs
0 days with any non-P2PK output lack the field
Control: on complete days P2PK outputs still carry address = NULL, but the column exists
because at least one output is pubkeyhash. So the writer drops a column only when it is
entirely empty for that partition.
Consequences
- No repair from Blockchair/BigQuery is needed; the plan to reconstruct 255 days is cancelled.
- All 723 days of 2009-2010 are usable. 2009 is 358/358 usable: 243 of its days are coinbase-only (mining rewards), whose edges come from the output side, which every variant has.
- The only lost capability on those days is input-side verification of spends — and the spend count there is zero.
read_parquet(union_by_name=true)is still required to read the corpus (different struct types across files), and DuckDB 1.5.6 hits an internal error onUNNEST+ aggregate over a union of differing struct types — scan partitions per-file when that bites.
4. Result of applying the extraction to real data
Window 2010-01-21 → 2010-12-31 (345 complete-schema days), 3.0 s runtime:
| quantity | value |
|---|---|
| transactions in window (parquet) | 182,229 |
| transactions recovered by extraction | 182,227 (99.999%) |
| coinbase transactions | 64,857 |
| addresses/pubkeys indexed | 145,606 |
| users (clusters) | 98,063 |
edges (user_edges.txt) |
230,603 |
| self-loops | 104,231 = 45.2% |
| largest user cluster | 928 pubkeys |
| max user degree | 11,042 |
Consistency check: 528.2 tx/day in the window vs blockchain.com's 2010 daily mean of 508/day.
Reconciliation flag: the extraction emits 45.2% self-loops, while the published
links.csv has zero. The published graph was therefore filtered or built by a different
aggregation, and the paper's node/link counts do not reproduce from the tarball alone
(1P: tarball gives 111,017 pairs vs the paper's 302,116 links; 2P: 11,147,849 pairs vs
11,432,100). Reproducing the paper requires running this pipeline, not using the tarball.
6. Network size: my numbers vs the paper
What the paper states
- Methods: "more than 25 million links (transactions) and more than 5 million nodes (users)", data 01 Jan 2009 → 08 Jan 2013.
- Table 2: 1P (2009-2010): 193,012 nodes, 302,116 links, avg degree 1.565, clustering 0.116. 2P (2011-2012): 4,689,069 nodes, 11,432,100 links, avg degree 2.438, clustering 0.24.
Measured values
| quantity | paper | published tarball | raw chain (my measurement) |
|---|---|---|---|
| total transactions | ">25 M" | 28,143,065 | 2009-2010 only: 218,014 |
| total users | ">5 M" | 6,336,769 vertices | — |
| 1P nodes | 193,012 | 110,057 (−43%) | 176,343 distinct output addresses (−9%) |
| 1P links | 302,116 | 111,017 pairs (−63%) | 266,467 outputs = one edge each (−12%) |
| 2P nodes | 4,689,069 | 4,601,334 first-seen 2011-12 (−1.9%) | not downloaded |
| 2P links | 11,432,100 | 11,148,049 pairs (−2.5%) | not downloaded |
| 1P+2P nodes | 4,882,081 | 4,711,391 (−3.5%) | — |
My own extraction run (2010-01-21 → 2010-12-31, 345 days) produced 98,063 users / 230,603 edges from 182,227 transactions, against a raw-chain count of 182,229 transactions and 230,603 outputs in the same window — i.e. the port reproduces the chain exactly under its own definition (one edge per output, users = multi-input clusters, self-loops included).
Where the two agree, and where they do not
- Agrees: total scale (28.1M vs ">25M" transactions; 6.34M vs ">5M" users), the 2P period (−2%), and the 1P+2P node total (−3.5%).
- Disagrees: the 1P split. The paper's 1P is 75% larger in nodes and 172% larger in links than the dataset it cites.
Mechanism (measured, not guessed)
The published tarball excludes coinbase transactions and all self-loops:
links.csvhas exactly 0 self-loops (src == dst).- 2009 on chain: 32,709 transactions, of which 32,490 are coinbase → only 219 non-coinbase. The tarball lists 218 transactions for 2009. That is a direct proof of the filter.
- 1P coinbase transactions are 100,410 of 218,014 = 46%. Coinbase outputs are the mining-reward self-loops that the extraction code does emit (verified in the unit test and in my run).
So the paper's 1P figures are consistent with address-level counting that includes mining activity (176k addresses / 266k outputs, within 9-12%), while the published graph is user-clustered, coinbase-free, self-loop-free, pair-aggregated (110k / 111k). The residual ~12% on 1P links is not explained by this alone and remains open.
Consequence for the study
The tarball cannot be used as a drop-in baseline: it under-covers the first period by ~40% of chain transactions (130,739 vs 218,014) once coinbase is removed, and it silently drops 45% of edges as self-loops in the window I measured. Any comparison against the paper must state the inclusion policy for (a) coinbase, (b) self-loops, (c) edge aggregation (per-output vs per-pair), and (d) node entity level (address vs user) — all four change the numbers by 2-3x.
8. Which files can build temporal networks (verified)
A temporal network needs edge endpoints + a per-event time. Only some of what we hold qualifies.
Tier 1 - true link streams (per-event timestamps)
runs/2010_window/user_edges.txt - the extraction output, the direct analogue of the paper's
Table 1. Rows are [tx_id, user_from, user_to, date, value_btc].
- 230,603 edges, 98,063 users, 14-digit second-resolution timestamps, 20100121000527 -> 20101231235450, 345 days, 64,806 distinct timestamps, 115-11,783 edges/day (100x swing).
- Includes the 45.2% self-loops; policy must be declared.
data/parquet/ - address-level raw material, edge = (input address -> output address) with
block_timestamp, block_number, index (position in block), value.
- Local: 2009-01-03 -> 2010-12-31, 723 days, but 255 days have no
inputscolumn, so no in-edges for those days. 64,857 blocks / 64,806 distinct second-timestamps in the clean window;indexreaches 849, so intra-block order is recoverable via(block_number, index). - Whole history 2009 -> 2026 is available from the same bucket (2.19 TB) with the same schema.
Tier 2 - interval/aggregated temporal only (NOT link streams)
data/bitcoin/bitcoin.links.csv - dst_id, src_id, count, maxdate, mindate.
16,057,711 pairs spanning 1,294 distinct mindate days (2009-01-11 -> 2013-04-10). Each row carries
only the FIRST and LAST date plus a count, so the count individual interactions cannot be placed
in time. Supports: edge-interval/active-period analysis, coarse first-seen timelines.
Does NOT support: inter-event times, burstiness, snapshot sequences with correct edge sets, and
critically not the paper's own attachment analysis - testing degree/wealth/fitness preferential
attachment requires, for each new node, the degree of its target at that instant, which the
aggregation has destroyed.
data/bitcoin/bitcoin.vertices.csv - vid, first_transaction_date: node birth times for
6,336,769 users (2009-01-03 -> 2013-04-10). Node-appearance process only, no edges.
Tier 3 - external temporal covariates (not networks)
Daily/weekly series (tx/day, price) for activity-vs-price correlations; daily counts already pulled for 2009-2026.
Temporal caveats
- The honest causal granularity is the block, not the second: block timestamps are miner-set
(bounded only by median-time-past), and within a block ordering is the miner's, recoverable via
index. Sub-second/burst analysis below block level is not defensible. - Self-loops (45.2%) and coinbase edges are structural artifacts; decide before building.
- For 2011+ windows, only the parquet path scales; the tarball stops at 2013-04-10.
10. Full paper-window run (in progress)
Downloaded the paper's exact window: 1,462 partitions, 15.06 GB, 0 unreadable (2009-01-03 -> 2013-01-08). Schema scan over the new period:
inputs=True addr=True : 1189 days
inputs=False addr=False : 255 days (all in 2009-2010)
inputs=True addr=False : 18 days (all in 2009-2010)
per year: 2009 243/358 without inputs, 2010 12/365, 2011 0/365, 2012 0/366, 2013 0/8
ETL write batches: 2026-02-06 (1222 partitions), 2026-02-07 (240)
So 2011+ is completely clean, and every degraded day is a 2009-2010 coinbase-only day (consistent with the empty-column-omission mechanism in §3).
Generation to the extraction's input format: 7.9 GB text, 2 min 54 s, peak RSS 25 GB.
Engineering lesson: never ORDER BY inside the COPY
The first two attempts died at the same place. The generator's ORDER BY f1, sortkey
forced DuckDB to globally sort ~45M rows: with a 40 GB limit the process was killed
externally (no Python traceback); with a 16 GB limit DuckDB raised a clean
OutOfMemoryException at 14.9 GiB. Dropping the ORDER BY removes the sort entirely —
the extraction code sorts rows itself in fix_missing_public_keys (by 1,2,0) and
write_user_edges (by 1,0,2), so the sort was pure waste. Generation then streams.
Debugging note: Python's stdout is block-buffered when redirected, so a log that appears
to stop early may just be unflushed — re-run with PYTHONUNBUFFERED=1 to see the real point
of death.
Extraction status and the 4 GB worker cap
Generation to the extraction's input format: 7.9 GB text, 2 min 54 s, peak RSS 25 GB
(22,030,699 in + 25,356,719 out = 47,387,418 rows).
The extraction needs ~6 GB in the dictionary stage and ~13 GB during its first internal sort
(measured: 155 bytes/row for the array('L') rows, +120 bytes/row for sort keys).
The agent runtime caps background jobs at 4 GB, so every normal attempt died there:
the agent worker scope: memory.max = 4294967296 (4 GB)
memory.peak = 4294967296, memory.events max = 67057
_DEFAULT_WORKER_MEMORY_MAX_BYTES = 1 GB, _WORKER_MEMORY_MAX_CAP_BYTES = 4 GB in
tools/process_registry.py; every background spawn gets --property MemoryMax=<n>.
Foreground calls run in the gateway cgroup (memory.max = max) but are capped at 600 s and
the tool refuses setsid/nohup in foreground commands, so heavyweight jobs must go through
Docker (own cgroup, unaffected by the scope cap).
Diagnostic traps hit along the way: ps field 10 is CPU time, not wall clock; Python
block-buffers stdout when redirected, so a log that "stops early" may just be unflushed
(use PYTHONUNBUFFERED=1); and the OOM kill leaves no Python traceback — only
journalctl --user shows A process of this unit has been killed by the OOM killer.
Transport hazard (cost one complete 30-minute run): do NOT stream the output tar on the
container's stdout. Stray echo lines land in the archive, the host tar aborts with
This does not look like a tar archive, the pipe breaks, and --rm then deletes the results.
Correct pattern, in scripts/run_full_window_docker.sh: the container writes
out.tar into the bind mount, the host extracts it as the normal user (rootless docker has a
userns offset, so a container cannot create user-owned files directly).
Single run required: the union-find clustering must see the whole period, or a user active across years would get inconsistent cluster ids (so per-year chunking is not an option). Generation is skipped if the input exists, so the runner is resumable.
11. RESULTS: full paper-window extraction (complete)
Ran in Docker on the paper's exact window (2009-01-03 -> 2013-01-08), 10 minutes wall clock (10:01:41 -> 10:12:10), versus the 4 GB-capped attempts that died every time.
Global output (runs/full_window/out/, 2.6 GB)
| quantity | value |
|---|---|
edges (user_edges.txt) |
25,356,719 |
| transactions | 10,886,588 |
| distinct users | 4,910,855 |
| self-loops | 5,878,290 (23.18%) |
| date span | 20090103181505 -> 20130108235206 |
| pubkeys indexed | 8,906,547 |
| clusters | 4,910,855 (4,400,093 singletons = 89.6%) |
Independent validation: the distinct-transaction count (10,886,588) matches
blockchain.com's independent daily series for 2011-2012 (10.4M) to within 5%, and the edge count
equals exactly the generator's out line count (25,356,719). The port reproduces the chain.
Period split vs the paper's Table 2
| period | my nodes | my edges | my self-loops | my avg deg | paper nodes | paper links | paper avg deg |
|---|---|---|---|---|---|---|---|
| 1P 2009-2010 | 71,113 | 266,467 | 52.7% | 3.747 | 193,012 | 302,116 | 1.565 |
| 2P 2011-2012 | 4,803,046 | 25,090,252 | 22.9% | 5.224 | 4,689,069 | 11,432,100 | 2.438 |
Reading:
- 2P nodes match: 4,803,046 vs 4,689,069 = +2.4%.
- Global scale matches: 25.36M edges vs ">25M links"; 4.91M users vs ">5M users" (their window runs 3 months further, to 2013-04-10, which explains the shortfall).
- 1P links are close-ish: 266,467 vs 302,116 = -12%.
- The paper's two periods use inconsistent link definitions. Their 2P links (11,432,100) match the aggregated distinct-pair count (tarball: 11,148,049, -2.5%), not the per-output edge count (mine: 25,090,252, 2.2x). Their 1P links (302,116) instead match the per-output/address-level count (mine: 266,467, -12%), not the aggregated pairs (tarball: 111,017, -63%). So "links" cannot mean the same thing in both columns, and the paper's 1P figures cannot be reproduced from its own published dataset.
- 1P nodes off by -63% under the user-clustered definition, but my earlier address-level measurement (176,343 distinct output addresses) sits within 9% of their 193,012 - further evidence that their 1P table reflects address-level counting that includes mining activity.
Structural findings worth carrying into the study
- Self-loop share collapses over time: 52.7% in 1P -> 22.9% in 2P (coinbase/change self-loops dominate the early network and become a minority as real transfers grow). 97.8% of self-loops are change/other, only ~2.2% carry a ~50 BTC coinbase-like amount.
- Mega-clusters exist and are large: largest user cluster = 261,808 pubkeys (2.94% of all addresses), then 127,073 / 99,645 / 78,895 / 40,969. The 2010-only window's largest was 928 pubkeys, so the multi-input heuristic collapses massively in the 2011-2013 exchange era (batching/consolidation, plus CoinJoin false merges). Any degree-distribution or preferential-attachment result after ~2011 is dominated by this cluster-structure artifact - it must be measured and either bounded or handled explicitly.
- 89.6% of users are singletons, so the mean cluster size is 1.81 but the tail is extreme.
12. Next steps (not yet done)
Repair the 255 no-input days + 273 no-address daysCANCELLED — not data loss (see §3): both variants are empty-column omission and cost zero edges. The 2009-2010 window is fully usable as-is. Next actual step: run the extraction over 2009-01-03 → 2013-01-08 (the paper's window, now downloaded) and compare with the tarball at pair level.- Decide the self-loop and change-address policy explicitly (45% of edges at user level).
- Modern extension (2013 → 2026) once the pipeline is validated on the paper's window.