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PoST Initialization

Proof Generation​

Once an epoch, after the node has received a PoET proof and during the PoET cycle gap, the node will generate a proof of spacetime, which requires that it sequentially read all of the PoST data. The details aren't something most miners need to worry about as the node will handle the process for you; see Fine-tuning Node Performance for information on benchmarks and parameters that can be tweaked.

The first part of the proving process is an initial proof of work phase called k2pow that uses a proof of work algorithm called RandomX. During this phase, which is CPU bound, you should see CPU usage spike briefly for a few minutes. There should be very little network or disk activity during this phase. As explained in the Profiler docs, it should take a low-end CPU around 2.5 minutes to compute k2pow for 4 SU; computation time scales linearly with the hash rate and number of storage units being proven. See the RandomX Benchmark to get a sense of your CPU's RandomX hash rate.

Once the k2pow phase is complete, the node begins the PoST proving process, which takes longer as it involves reading and computing a hash function over all the committed PoST data. How long depends on factors including the disk read speed, CPU speed, and configured nonces and threads. This process may be CPU bound or IO bound, depending on the configuration. (It also doesn't touch the network.)

Initialization​

The most important part of becoming a smesher is the PoST initialization (sometimes referred to as "plotting"). This process requires a GPU and is designed to be costly and time-consuming due to the crypto-economic design of the protocol. As described above, unlike in proof of stake networks, there's no "slashing" (burning a portion of stake) in the Spacemesh protocol. Instead, the sanction for engaging in malicious behavior such as equivocation is invalidation of a smesher ID, which invalidates all of the PoST data associated with that ID. In order for this sanction to be costly, performing PoST initialization and generating PoST data must also be costly.

Note that initialization can theoretically be performed using a CPU (as opposed to a GPU), but it will take so long that this option isn't viable for the vast majority of miners.

OpenCL​

PoST initialization requires support for OpenCL. Installation instructions will vary depending upon your operating system, platform, and GPU hardware. A good starting place for Linux users is this wiki page. On Ubuntu and other Debian-compatible systems it may be enough to install these packages:

> sudo apt-get update
> sudo apt-get install ocl-icd-libopencl1 opencl-headers clinfo

To test if OpenCL is installed and configured correctly on your system, try running clinfo. You should see output similar to the following:

> clinfo -l
Platform #0: NVIDIA CUDA
 `-- Device #0: NVIDIA GeForce RTX 2060 SUPER

macOS Overview​

For macOS users, OpenCL is bundled with the system, and the framework is available out of the box on macOS version 10.6 (Snow Leopard) and later. Therefore, explicit installation of OpenCL is generally not required. However, to ensure compatibility and optimal performance with your specific hardware and software setup, you might need to update your macOS.

Steps​
  • Update macOS: Keep your macOS up to date to ensure you have the latest OpenCL framework versions and GPU drivers. You can check for updates in the “Software Update” section of System Preferences.
  • Use clinfo: To verify the OpenCL configuration, you can install clinfo using the command brew install clinfo. Then, run clinfo in the terminal to check the available OpenCL platforms and devices.

Windows Installation Overview​

Installing OpenCL on Windows requires manual GPU drivers updates, as the operating system does not include these drivers by default. The process is similar across different GPU manufacturers but requires visiting the specific manufacturer’s website to download the appropriate drivers.

Steps​
  • Download Drivers: Navigate to your GPU manufacturer’s website (NVIDIA, AMD, or Intel).
  • Select your GPU model and download the latest drivers that include the OpenCL runtime support.
  • Install the Drivers: Execute the downloaded installer and follow the on-screen instructions to complete the installation. Make sure any options related to OpenCL support are selected if given a choice.
  • Verification
  • After installation, use the clinfo command on Windows to check for OpenCL support. This utility will list all OpenCL-compatible devices on your system and provide detailed information, confirming a successful installation.

Troubleshooting​

Issues with OpenCL can often be resolved by ensuring your GPU drivers are fully up to date. Check your hardware’s compatibility with the version of OpenCL you’re using and look for any software that might conflict with your drivers. For specific problems, the support documentation and forums for NVIDIA, AMD, or Intel may offer solutions.

Initialization Speed​

The amount of time it takes to complete PoST initialization depends upon a number of factors including GPU model, hard drive write speed, and the number of storage units being initialized. As a rule of thumb, Nvidia RTX 3090 cards can initialize around 3-4 MB/s and 4090 cards can initialize around 6-7 MB/s. Community crowd-sourced benchmarks are available for a wide range of cards. Note that hard drive write speeds tend to be much faster than GPU throughput, so this should not limit the initialization speed unless the drive is exceptionally slow or exceptionally busy.

Choice of Filesystem​

In general Spacemesh is agnostic to the choice of filesystem. You can successfully initialize and run an identity and manage the underlying PoST data on any Linux, Windows, or macOS-compatible filesystem. However, you should keep two things in mind when choosing a filesystem.

  1. If there is any chance you will want to move the identity from one operating system to another, we strongly recommend using the exFAT filesystem. This is the only filesystem that works out of the box across all the major operating systems. Keep in mind that copying an entire identity from one filesystem to another could take a very long time, whereas with an exFAT filesystem you can just "plug and chug" on any computer. You should be able to initialize and format a new exFAT filesystem easily in any operating system.
  2. Different file systems utilize space differently and require different amounts of overhead. As such, the number of storage units you will be able to fit on a given disk will depend to some extent upon the filesystem used to format the disk. In our personal experience, we've found that exFAT is more efficient than EXT4, and may allow one extra storage unit to be placed on the same physical disk.

We also recommend that you not encrypt the drive or partition used to store the PoST data. You should of course protect the local.key file (which contains a miner's private key and is located in the node_data/identities folder) and not allow it to fall into anyone else's hands, but full drive encryption feels like overkill and could slow down proof generation.

Number of Units​

Determining exactly how many storage units fit on a drive is actually somewhat non-trivial if you want to maximize the amount of PoST data you can fit on a drive, maximize the identity size, and maximize the rewards. For one thing, PoST identity file sizes are base 2 (e.g., 64GiB) whereas the size of most hard drives is base-10 (e.g., 1TB). Moreover, as described in the previous section, different file systems use space differently and require different amounts of overhead.

Linux users may find a command such as the following helpful in displaying the available space on a drive:

> df -B GiB /dev/sda
Filesystem     1GiB-blocks    Used Available Use% Mounted on
/dev/sda           3667GiB 3649GiB     19GiB 100% /mnt/smesher-01

As you can see, this 4TB drive, which should contain 3725.29 GiB, in fact only contains a usable 3667 GiB. After initializing 57 storage units of 64 GiB each, it contains around 19 GiB free usable space.

Linux users may also find the tune2fs command useful, both for displaying more detailed filesystem information and for reducing the amount of reserved space on a drive. Assuming a drive is exclusively being used to store PoST data, the reserved space may safely be set to zero. For example, for the above drive /dev/sda:

> sudo tune2fs -m 0 /dev/sda

Wanted: Please fill in information on how to do the same on macOS and Windows.

Starting Initialization​

As with most other aspects of Spacemesh, the easiest way to begin and monitor initialization is using the Smapp application. When you first open it, Smapp will walk you through the process of choosing a location for your PoST data, choosing your GPU, and beginning initialization. It'll show you the progress as initialization proceeds. See Smapp Tutorial #4: Proof of Space & Smeshing Setup for more information on this process.

If you prefer to perform PoST initialization using the command line, you have two options. If you simply run go-spacemesh directly with the smeshing configuration parameters specified above, it'll perform initialization for you using the fastest GPU. You can also manually perform initialization using the postcli tool, which allows you to have even greater control of the initialization process, such as running in parallel across multiple systems or multiple GPUs (more information on this below).

Choosing a Provider​

As mentioned, go-spacemesh will automatically choose the fastest GPU to perform initialization based on a benchmark. You can change the selected GPU with the smeshing-opts-provider config item. To see the list of detected GPUs and their corresponding indices, run postcli as follows. You should see something like the following:

> postcli -printProviders
([]postrs.Provider) (len=3 cap=3) {
 (postrs.Provider) {
  ID: (uint) 0,
  Model: (string) (len=44) "[GPU] NVIDIA CUDA/NVIDIA GeForce RTX 3080 Ti",
  DeviceType: (postrs.DeviceClass) GPU
 },
 (postrs.Provider) {
  ID: (uint) 1,
  Model: (string) (len=44) "[GPU] NVIDIA CUDA/NVIDIA GeForce RTX 3080 Ti",
  DeviceType: (postrs.DeviceClass) GPU
 },
 (postrs.Provider) {
  ID: (uint) 4294967295,
  Model: (string) (len=17) "[CPU] scrypt-jane",
  DeviceType: (postrs.DeviceClass) CPU
 }
}

The first two (with IDs 0 and 1) are the GPUs; the last (with ID 4294967295) is the CPU. To select the second GPU with ID 1, use the following config:

  "smeshing": {
    "smeshing-opts": {
      "smeshing-opts-datadir": "<post_data_directory>",
      "smeshing-opts-maxfilesize": <post_file_size>,
      "smeshing-opts-numunits": <post_num_units>,
      "smeshing-opts-provider": 1
    },
    ...
  },

Resizing PoST​

The size of the data used for proof generation can be changed after initialization. This is useful if you want to add more storage units to your identity, or if you want to reduce the number of storage units to free up space on your drive. To do this, you can change the numunits parameter in the smeshing-opts section of the config.json file. Stop your node, change the config file, and restart the node. The node will automatically resize the PoST data to the new size:

  "smeshing": {
    "smeshing-opts": {
      "smeshing-opts-datadir": "<post_data_directory>",
      "smeshing-opts-maxfilesize": <post_file_size>,
      "smeshing-opts-numunits": <new_num_units>,
      "smeshing-opts-provider": "<gpu_id>"
    },
    ...
  },

Info: Resizing PoST data is a time-consuming process during which the node is not able to generate proofs. The node will automatically generate proofs once the resizing process is complete. Time your resizing process accordingly - start after your PoET cycle gap ends and the node has generated a PoST proof and finish before the next PoET cycle gap.

Be aware: Decreasing your PoST size will reduce your rewards and becomes affective in the epoch after the resizing process is complete and the node has generated a PoST proof. Increasing your PoST size will increase your rewards, but it takes 2 epochs to become effective. Example: If you increase your PoST size before the PoET cycle gap in epoch 10, your rewards will be increased starting from epoch 12.

You can also resize PoST data using the postcli tool, which allows you to have greater control. For information on how to initialize only the data you don't already have and merge it with the existing data refer to the section Initializing a subset of post data.