Dr -ck

Congratulations to miner bc1q~ucu6 for solving the 318th stubborn block at solo.ckpool.org with only ~16.4TH of hashrate on a 6.2TH worker! A miner of this size has less than a one in 3400 chance of solving a block in a year.

https://mempool.space/block/00000000000000000001b6d3ff91f983eef84b14ad428c60fbf0722b5215f360

A debt clock for Australia inspired by the usdebtclock website. Non-partisan, just data.

https://audebtclock.org

Congratulations to miner bc1qdyqjq9qccp34pyv3kxmsrkn7p0amnsqqy8kdeq with a wildly variable - presumably rental - hashrate peaking at 100PH for solving the 317th solo block at http://solo.ckpool.org!

Despite the chaos from the hardware wallet exploit, bitcoin just keeps on doing its tick-tock next block.

https://mempool.space/block/0000000000000000000081c26d870f8ac4a0217b8c6dab7b63c25f03b3882c52

Stratum V2 is now live on all http://solo.ckpool.org servers after extensive validation and testing - thanks to all who pointed their hashrate to the experimental server. Regular stratum (V1) mining continues unaffected. Restarts also would have caused no discernible downtime to miners.

SV2 is accessible on the unified stratum URL on discrete ports: stratum2+tcp://stratum.ckpool.org:3336/9anrRNhBh7869XtNnFcCuGBRZP51E635qGbu457J5kHdszhfRc3 and port 4336 for highdiff mining rentals only.

As per stratum V1, you will be directed to the lowest latency pool for your location.

Job declaration is supported on port 3337 but I am recommending against using it until further stratum V2 developments make it sensible to use on a solo pool.

The sv2solo domain used by testers will keep working as an alias to the stratum domain so you need not reconfigure your miners if they're already connected.

Final shout-out and thanks goes to mineracks for providing hardware and hosting for the AU server, and dealing with my demanding support requests.

Mine on!

Congratulations to miner bc1qe6f2z5vd5c3spdqrstf9m8sf5zzztgerl2uzzd with ~6PH for solving the 316th solo block on EU solo.ckpool.org! A miner of this size a 1 in 900 chance of solving a block per day.

https://mempool.space/block/0000000000000000000146c469ee9ebff4e4e3e075de978d25846005e5860e75

https://solo.ckpool.org now has a unified stratum endpoint for all the servers at stratum.ckpool.org. This will automatically choose the lowest latency pool for your endpoint, and fail over to the next nearest in the unlikely event of any outage or internet routing issue.

Stratum connections are very long-lived, so if you do fail over, you may not fail back even when the best pool is available again.

You may still use the existing direct configurations to each of the pools but without the advantage of failover support. It will however guarantee you only ever connect to the endpoint of your choice.

For anyone mining at @Rigly's blockparty, know that you can mine at any of the the solo ckpools as they combine stats and the aggregated stats will be at https://stats.ckpool.org/users/3Gk1GfP3bHA6M2ZzK5mHdqbWN1iNsqAenH. The raw stats are here: http://raw.stats.ckpool.org/users/3Gk1GfP3bHA6M2ZzK5mHdqbWN1iNsqAenH

Congratulations to RiglyBlockParty with 150PH from their combined party for mining solo block 315 at http://solo.ckpool.org! This much hashrate has about a 1 in 50 chance of mining a block each day.

https://mempool.space/block/00000000000000000001089806eb0365ac250e44bc0b306ba0339a6b63c63fc5

All solo stats are now only available on the one GUI stats site to rule them all stats.ckpool.org. Redirects are in place from the old stats domain names to direct to the one stats server. The raw pool stats remain on each pool if access is still desired. Mine on!

New sgsolo.ckpool.org optimised for solo miners in Asia & The Middle East! Stats will appear in the updated combined stats.ckpool.org which covers all solo ckpools. This now gives the solo ckpools good low latency coverage from most parts of the world. Instead of having many nodes scattered throughout the world, each node is a very high performance machine on a high speed network in select locations for the best coverage overall, and interconnected via a a custom low latency block propagation network. The pools are: solo.ckpool.org for The Americas eusolo.ckpool.org for Europe & Africa sgsolo.ckpool.org for Asia & The Middle East ausolo.ckpool.org for Oceania. Choose the one closest to you, and feel free to use the next nearest as a backup pool! Mine on!

New stats site for testing: http://stats.ckpool.org . This site aggregates the statistics for all solo pools on one page. Assuming everything works as planned, it will replace the need for separate stats sites for each solo pool, making it easier to deploy more locations.

Congratulations to miner 3Qef~LfPJg for solving the 314th solo block at solo.ckpool.org! This was a big miner who's been renting 500PH for the last 5 hours.

https://mempool.space/block/00000000000000000000c63fa7d726a1840c777a59ebc73f45a298989f78548a

Ckpool upgraded to faster yyjson library.

Whilst ckpool is very low overhead and scalable due to being coded in multithreaded C, one of the largest overheads within the code is the json parsing library. Libjansson has been included since 2014 and it touches approximately 5,000 lines of code with ckpool.

Since that time a number of higher performance json libraries have come out, with yyjson proving to be the fastest - 10-100x faster depending on the workload. I've resisted reworking the code for a long time, but the benefits are substantial - not only would ckpool be much lower overhead and even more scalable, it would lead to faster block template changes which are a critical performance measure in mining pools.

I've replaced all the performance critical json in the main pool code and the bitcoin daemon parsing, leaving other modes (proxy, passthrough, node, etc.) to use the old code, and have addressed all the potential memory leaks. This is the most substantial code change to ckpool in many years. The diffstat tells the story - 15 files changed, 1167 insertions(+), 587 deletions(-), not including the library code itself. The code has been merged into the master branch and is ready for use.

The updated ckpool code has no known outstanding issues and is running very smoothly on all the solo pools solo.ckpool.org, eusolo.ckpool.org, and ausolo.ckpool.org. Not only are block changes occurring 30-50ms faster than previously, ckpool is using approximately 2/3 of the CPU, giving a 50% mining client capacity increase.

It's worth pointing out that the updated ckpool code will actually benefit low power machines running ckpool even more, so if you're running a local instance of ckpool it is worth upgrading.

Now let's churn out some more blocks. Mine on!

Congratulations to miner bc1q~edvj with only 70TH for solving the 313th solo block at http://eusolo.ckpool.org! A miner of this size has only a 1 in ~100,000 chance of solving a block per day, or once every 300 years!

https://mempool.space/block/000000000000000000012d5e7b4745f92b9cd60241854e38be68d9b182feabcb

I'm planning to rework the http://ausolo.ckpool.org networking this afternoon. There will be a period of downtime while this happens, and when it returns it will likely be on a different IP address so it may take a while for your miners to recognise the change. As always, make sure to have a backup pool configured in your mining hardware.

Lrzip version 0.660

https://github.com/ckolivas/lrzip/tree/v0.660

Lrzip is an ancient command line compression tool I created for linux based on the original Rzip tool designed to use maximum resources on modern hardware for high levels of compression in the least possible time, with optional secure encryption, and have been maintaining on and off for many years. I finally found the time to give it a long overdue maintenance and security bugfix update. All existing users are urged to update. Get it while it's hot.

I've removed the separate ckpool-solo repository from bitbucket to avoid confusion. It has long since been merged into the master ckpool branch with the same code so you will be redirected to that if you try to access it. https://bitbucket.org/ckolivas/ckpool/src/master/

eusolostats.ckpool.org has been migrated to the more powerful server. Assuming everything is working fine you should notice no difference.

There may be a small interruption to your statistics that occurred during the migration period. Cached local DNS on your browsers means you may not immediately switch to the new server.

solo.ckpool.org updates.

The EU solostats server is running low on disk space, so I intend to migrate it to a virtual subdomain on the much higher powered server running the main solostats.

The AU solo server's network performance is not meeting my expectations so it will be reconfigured over the next few days and there will be a short downtime. I will be providing notification where possible. As always, make sure to have a backup pool specified on your miners.

solo.ckpool.org updates. The EU solostats server is running low on disk space, so I intend to migrate it to a virtual subdomain on the much higher powered server running the main solostats. The AU solo server's network performance is not meeting my expectations so it will be reconfigured over the next few days and there will be a short downtime. I will be providing notification where possible. As always, make sure to have a backup pool specified on your miners.

Be aware there is always trust involved when you mine at a pool, more so for solo blocks. New pools keep springing up without any reputation and make great offers. The least you can do is check what address the pool is mining to, if it claims to be mining solo blocks for you.

https://skot.github.io/pool_checkr/

Congratulations to miner 1Ng9~VoQz with 270TH for solving the 311th solo block at solo.ckpool.org! A miner of this size has a 1 in 30,000 chance of solving a block per day.

https://mempool.space/block/000000000000000000001ac9929c4d1aa62610efe8dd18837fdf445b3c47f5cf

Congratulations to miner bc1q~aalj with ~200TH for solving the 310th solo block on the eusolo.ckpool.org server! A miner of this size has a 1 in ~35K chance of solving a block each day.

https://mempool.space/block/0000000000000000000128b8e814ce04f8b9b61ef4485023028afebfcf6bb4a8

Congratulations to miner bc1q~xv9n with ~700TH for solving the 309th solo block at solo.ckpool.org! A miner of this size has a 1 in 10,000 chance of solving a block each day.

https://mempool.space/block/00000000000000000000a8e30a009cd15c7c8ee207cfc352eac02e653e182ba5

Congratulations to extremely lucky miner 3K99~Ct8M with only SIX TH for solving the 308th solo block at http://solo.ckpool.org. A miner of this size has only a a in 180 million chance of solving a block each day!

https://mempool.space/block/00000000000000000001457a4acc5da8e886dddd0a79a6899957a502e0a1977b

Congratulations to miner bc1q~jr38 for solving the 307th solo block at solo.ckpool.org, with only 200TH!

https://mempool.space/block/0000000000000000000180aab2a364d0baeddacf4048d0600065390a81651829

A miner of this size only has a 1 in ~36,000 chance of solving a block each day, or once every ~100 years!

Congratulations to massive new rental miner bc1q~4kzx for solving the 306th solo block at http://solo.ckpool.org!

https://mempool.space/block/00000000000000000000978f2aa548b12b9fe7da9e2809d25f2d40ddfb63c1ae

Sub 1sat/vB transaction discussion and reversal of decision to mine them on solo ckpool.

Block 910440 https://mempool.space/block/00000000000000000000d22167aa0c9d1a49e7878631d6c93ea1b1c87b98ba24 is the first block that solo ckpool has mined that has included sub 1sat/vB transactions. I made this change because the bulk of the mining pools are now mining transactions below the default (until now) mempool policy of mining transactions only 1sat/vB or above. The reason for switching solo ckpool was partially out of necessity - if the mempool differs substantially from what other pools are mining, when other pools mine a block with low fee transactions, solo ckpool will be slow to build new blocks. The reason is because of the disparity in what is in the pool's mempool and it missing transactions included, so it would have to ask for the missing transactions before it can build a full block.

Now that solo ckpool has mined a block with sub 1sat/vB transactions I have data on the reward mined as the result of a low transaction fee period. Of the ~4900 transactions mined in this block, ~3300 were sub 1sat/vB transactions. It took some time to sift through the data of these transactions to determine what the mined fees were. They amounted to ~.0018 BTC more in fees, or ~$220. This is ~.06% of the current 3.125 BTC block reward.

These particular low fee transactions were very small and appeared to create 1-2 UTXOs each.

In light of how ridiculously small the extra fees mined were by accepting these transactions, and the potential for creating a significant number of new UTXOs, I am reversing my decision to mine these transactions. To maintain solo ckpool's ability to be aware of these transactions in the mempool I will only be setting the minrelaytxfee to accept and forward them, but not setting a lower blockmintxfee to mine them.

The block reward needs to have dropped substantially for such low fee transactions to add meaningful reward to mining pools, and I would only consider doing so if the reward was at least 1% more. The block reward would need to have dropped below 0.2 BTC total meaning we are decades away from such fees to be significant. By that time the landscape is likely to be very different to the current one, and it is unknown if fees will remain low that far away. A lower minimum fee is also likely to worsen fees' ability to be a significant contributor to mining rewards as block subsidy diminishes.

I implore other pool owners to do their own calculations and reconsider their decision to mine them at this stage.

Create your own local solo bitcoin mining ckpool & bitcoind easy install

It's clear that the default ckpool installation requires a bit of linux knowhow so I've created an all-in-one script to automate the process for you.

Quick instructions for most linux distributions: wget https://bitbucket.org/ckolivas/ckpool/raw/master/scripts/install-ckpool-solo.sh chmod +x install-ckpool-solo.sh sudo ./install-ckpool-solo.sh

Whilst a dedicated high performance pool for regular or solo mining is still likely the preferred option for most people, everyone should have the ability to run their own truly solo mining operation even if just as their final backup. It should also be easy for as many people as possible to deploy one quickly in the case of an existential mining threat.

This will download ckpool source code, v29.0 bitcoin daemon binary, check its validity, install the daemon, build ckpool, and install it, configured for solo mining, and begin downloading the blockchain. Follow the prompts or simply press enter for the default settings.

Should work on any .deb or .rpm based linux distribution (ubuntu, debian, fedora, centos, rhel) to download required packages. Installs both as systemd services as the current user but can configure a new ckpool user for both. It will allow you to choose to run a pruned bitcoin blockchain to minimise hard drive storage, but it is recommended to use a full blockchain and have enough storage space to spare. The current blockchain is almost 700GB, so ideally you should at least have double this space on the drive. You will be given the option to use a checkpoint hash to speed up the initial blockchain download, or disable it for maximum paranoia. It will use any existing blockchain data in ~/.bitcoin if it exists for the chosen user.

Bitcoind will be preconfigured with suitable mining defaults, and ckpool will be configured to start in solo mining mode on port 3333 on the current machine. You will be unable to mine to it until the bitcoin daemon has synced up the full blockchain.

You will be given the option to enable donation to the ckpool author, and a custom signature to be added to any solved blocks.

Higher performance modern computing hardware and storage is recommended if you are to maintain a dedicated local solo mine and not just a backup of last resort.

Congratulations to the 2nd solo block solver 35mU~8hK7 in 2 days for solving the 304th solo block at https://solo.ckpool.org! This was a huge miner with 270PH at the time of solving the block.

https://mempool.space/block/00000000000000000001e6a5aec8788183793b27370ef638b152b4d02f9f0787

A miner of this size has about a 1 in 20 chance of solving a block each day, however this miner doesn't appear to have been mining continuously at that hashrate for very long, and the worker size suggests this was a rental.https://m.primal.net/RHxB.png

Congratulations to miner 35Wu~yPhF for solving the 303rd solo block at the EU https://solo.ckpool.org with only 49TH! https://mempool.space/block/000000000000000000012b46e1a7ce322e850afde12422c440ee19d9c1b6d74a A miner of this size only has a one in 130,000 chance of solving a block in a year or once every 370 years on average!

Congratulations to miner 35ny~zePa with an enormous 200PH for solving the 302nd solo block solved at https://solo.ckpool.org!

https://mempool.space/block/0000000000000000000161bc7461e9736bcda0f28458bd75265019864961aefb

A miner of this size would solve a block once every ~35 days on average at current mining difficulty.

Announcing ausolo.ckpool.org, another sibling solo ckpool located in Brisbane, Australia to service Oceania/Asia-Pacific miners with low latency solo mining. Just point your miner to: ausolo.ckpool.org port: 3333

This is a standalone pool from solo.ckpool.org and eusolo.ckpool.org for latency and performance reasons, but blocks will be propagated between the sibling pools and you can use each sibling pool as a backup if desired.

Blocks mined from ausolo will feature the same solo.ckpool.org signature with a ckpoolau prefix.

I fully expect this to be the lowest hashrate solo ckpool consisting mostly of bitaxed sized miners given the electricity prices of Au, but since most of them will be wanting to mine solo, this should fill the gap in the region.

There is now solo.ckpool.org coverage with relatively low latency to most parts of the world.

The hardware for ausolo has been provided and is being maintained courtesy of mineracks.com

Mine on, and good luck!

Any solo bitcoin miners out there interested in me opening an AU based solo ckpool for miners in the Oceania/Asia-Pacific region?

It's now been just over 15 years since I first contributed patches to cpuminer as my entry into the bitcoin world. What a ride it's been, and it still feels like we're just getting started.

A block party aiming for a combined total hashrate of 7EH on solo.ckpool.org is planned for this Saturday the 5th. It's being coordinated here https://upendo.rigly.io/

Saturn captured in RGB mono 2025-06-10 UTC.

Saturn captured on 2025-06-10 UTC. The rings are now just barely visible.

If it wasn't clear, I will continue to run core relay/mempool rules on the solo pools as I always have for all the technical reasons already outlined in a myriad of other places.

By all means feel free to run whatever client you feel is appropriate or mine wherever you like, but I implore you to read arguments instead of listening to them for the person delivering verbal messages can have more influence on your decision making than it can in text.

solo.ckpool.org and eusolo.ckpool.org have had trivial updates and new new bitcoin daemons and restarted uneventfully. Mine on!

Saturn in composite colour infrared captured this morning, 2025-06-10 UTC.

Congratulations to miner bc1qa8r4up9nchkvdnhcf9feexv2jfantrk48ef374 who recently ramped up hashrate for solving the 300th block solved at http://solo.ckpool.org!

https://mempool.space/block/000000000000000000020c5281e68cbf5b382e02e3a42d4a9d2965b08d1f8bb3

I've updated the stats pages for http://solo.ckpool.org and http://eusolo.ckpool.org to display SI unit prefixes.

Saturn captured 2025-05-18.

https://m.primal.net/QwYp.jpg https://m.primal.net/QwYq.jpg https://m.primal.net/QwYr.jpg https://m.primal.net/QwYs.jpg

Venus captured in ultraviolet and infrared this morning 2025-05-14. Venus is plain white in visible light but a composite colour UV+IR image can show up cloud details.

Saturn captured this morning 2025-05-12. I've added a version with gamma applied which makes the very thin rings visible.

This is a great new multisig hardware wallet device one of the local bitdevs in our meetup has been working on and is coming out soon. Uses taproot and allows dynamic adding and removing signatures.

https://frostsnap.com/

Try again. Venus from this morning 2025-05-11 in infrared, this time with correct caption.https://m.primal.net/Qtvg.jpg

Venus captured in infrared this morning 2025-05-11.https://m.primal.net/QtvP.jpg

First Saturn images of its new season. Saturn is almost edge on this year so its rings reflect hardly any light, making them virtually disappear with normal exposures. Here are my captures in visible light and near infrared from early this morning.

Congratulations to miner bc1~nnc5 with ~230TH for solving the 299th solo block mined at http://solo.ckpool.org! A miner of this size has about a 1 in 30,000 chance of finding a block each day.

https://mempool.space/block/000000000000000000003d9a1a59f93a992c0858d3d15627a87fe5649b76563e

Congratulations to miner bc1qq926qlrhc2pvxzc5f0zswnvqqddqqj3tz2amla with a sizeable 2.5PH/s for solving the first EU solo block and the 298th block at solo.ckpool.org!

https://mempool.space/block/000000000000000000005afed55b551d961220653a05daa8f362de2a384d8cea

A miner of this size has about a one in 2,000 chance if finding a block per day.

Congratulations to a super lucky miner bc1qaxccz85rx6ywy2xw6ugtm6u37mvew6qqn7lgtd with only 3.3TH who solved the 297th solo block at https://solo.ckpool.org with a 480GH bitaxe!

https://mempool.space/block/000000000000000000006414aea39be567cf1d5ff6cbf2d77254fe7c714b0d81

A miner of this size has only less than a 1 in a million chance of finding a block per day, or put alternatively, would take 3500 years to find a block on average.

The new server has been deployed and the dedicated http://eusolo.ckpool.org for miners in Europe and Africa is now active once more. Miners need not make any configuration changes. You may need to restart your mining hardware for it to reconnect to the new server.

Congratulations to massive miner bc1qa8r4up9nchkvdnhcf9feexv2jfantrk48ef374 (probably a rental) with 85PH for solving the 296th solo block solved at http://solo.ckpool.org https://mempool.space/block/000000000000000000022247ce3898fc9e10be0161cde5f369293d7a916ca8b3

Update re the EU solo pool. Everyone mining to eusolo.ckpool.org is currently directed to the main pool solo.ckpool.org as it was rapidly decommissioned by the original donor. The new hardware was meant to take 3 days to provision but my provider has already set it up. I'll get to work at deploying the pool as soon as possible.

Re: http://eusolo.ckpool.org, sadly the anonymous individual who offered to fund the server's running has retracted their offer. This & the stats incident has confirmed my belief I should not rely on others. I will likely now fund it myself but will need to migrate the service.

Congratulations to massive miner 3FK6JGHQpvqQatbpzje1yUbPbV9m1YjoKq with 50PH for solving the 295th solo block at http://solo.ckpool.org. A miner this size would solve a block every ~100 days on average

https://mempool.space/block/000000000000000000008659827d9d3e3f98cb6428ce5149464b44125be5ce19

Prove to me you don't understand why bitcoin and not shitcoins without saying you don't understand bitcoin...

Amazing. This quote showed from David Marcus great insight and was completely unexpected regarding the failure of Libra - Meta's planned shitcoin.

The EU solo ckpool is up and running! Connect to the pool via instructions at http://eusolo.ckpool.org. Graphical stats available at http://eusolostats.ckpool.org. Miners in Europe and Africa are encouraged to move to the new pool. Miners in The Americas and Asia-Pacific should still use http://solo.ckpool.org but the sister pool can be used as backup.

This is an entirely separate pool from http://solo.ckpool.org and neither shares nor stats are shared across instances for overhead reasons. They only help propagate each others' blocks. Both will solve blocks with the same coinbase signature though.

Here's a little podcast I did with bitcoin mining world.

I've tentatively set up a new stats site courtesy of MrV_777 for trial. I'm personally hosting this one, but I've left his donation link intact since he did the work. Some other web devs are also working on alternatives, so do not assume this is the final form but please test it out. I may be hosting multiple in the future whilst testing them out.

Http only for now:

http://solostats.ckpool.org

Saturn captured in excellent conditions 2024-09-27

A phenomenon known as the Seeliger effect means Saturn's rings appear brighter when it's at its closest approach to Earth. This animated gif shows the alternating captures at opposition 2024 and two weeks later demonstrating this effect.

Anyone using the solostats website for stats on http://solo.ckpool.org should know that it was being maintained by a 3rd party and in the last day they briefly put up a fee scheme which was not sanctioned by me and the breach of trust has made me decide to pull endorsement of it for now.

Trust is very difficult to obtain in this space, and whilst it was probably a simple error of judgement, I'd find it hard to resume endorsing the site. The simple text stats available directly from the solo.ckpool.org site remain available as always.

One of my best captures of the year in very good conditions of Saturn close to its closest approach to us on 2024-09-09.https://m.primal.net/KnPE.jpg

Bitcoin mining difficulty rose to a new all time high of ~92.7 trillion.

Congratulations to miner 3Ea12CGa2T1xRchP4zyng684CcqbicFUeJ with a massive 82PH for solving the 292nd solo block at solo.ckpool.org !

https://mempool.space/block/00000000000000000002bbf819cea419c9e3bb0d3f912fe32d655a1d2439a985

This is a screenshot of the pool logs at the time of the blocksolve.

People occasionally ask me what to do about diff and what the high diff port (4334) on solo ckpool is ideal for.

To clarify: the diff you mine at makes absolutely no difference to your chance at finding a block. In addition shares with solo mining have no intrinsic value and are purely for feedback to know you're mining at the pool. The high diff port has a starting diff of one million and is set that high simply because rental mining services demand that high. Only pethahash sized miners should consider using the port if they are consolidating their hashrate through a proxy - otherwise even if you're an exahash sized miner with every discrete miner connecting to the pool you should still use the regular port.

The other question that comes up is whether you can set your diff manually - the answer is yes if you use cgminer directly since I implemented the stratum protocol suggest-diff option within cgminer and ckpool. However again it is of no real use apart from getting the diff closer to matching your hardware earlier on as the pool will automatically adjust with time to an optimal diff (also purely cosmetic) though it may take a while if you're a tiny miner.

The final question is what to do if no hashrate or statistics ever show up on the pool - usually that's because people are mining with ridiculously low hashrates, GPU or CPU miners or most commonly nerdminers. The answer there is - don't do that. Just don't mine with such small hashrates as it's beyond the level of lotto mining into the ludicrously improbable chance of finding a block.

Saturn captured on 2024-08-18

Saturn captured in composite infrared 2024-08-18

Saturn captured in infrared 2024-08-18

Weirdly people see the ckpool project is 10 years old and think the code is 10 years old when it's actively maintained. I don't support any external ckpool docker containers maintained by anyone else that are out there.

The code as is published, is used directly on solo ckpool:

https://bitbucket.org/ckolivas/ckpool/src/master/

Saturn & inner moons captured 2024-08-18