GPU mining knowledge: Mining problems caused by DAG files

Many people who use graphics card miners to mine Ethereum may encounter the problem that the DAG file keeps growing, which eventually leads to insufficient graphics card cache and makes it impossible to mine. In fact, this DAG refers to "directed acyclic graph technology", which is a common problem in Ethereum mining. Today we will popularize this problem.

There is never a lack of professional technical terms in the blockchain field, such as asymmetric encryption technology, sharding technology, DAG technology... Today, we will introduce you to a new blockchain technology - DAG technology.

For a long time, public chains have been plagued by problems such as slow processing speed, high costs, and potential security risks. Without a safe, reliable, and efficient public chain, the development of the entire blockchain industry will be severely restricted. In this context, DAG technology came into being and was used to solve various problems on the public chain.

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The difference between blockchain and DAG

DAG, or directed acyclic graph, is a distributed ledger technology different from the mainstream blockchain. It upgrades synchronous accounting to asynchronous accounting. Many people believe that it can solve the high concurrency problem of traditional blockchain and is an innovation in blockchain from capacity to speed.

Using DAG as the network foundation solves the limitations of blockchain. This allows blockchain to be infinitely scalable at a tiny cost. Payments can be processed very quickly. However, only a small number of cryptocurrencies are currently using the next-generation DAG architecture.

Compared with the current public chain technology, DAG is actually the difference between a graph and a chain. For a chain, it is impossible to process only one part, because the chain has only one in-degree and out-degree, and the nodes on the chain cannot be split into several nodes for processing. However, for a graph, it is possible, because a graph can have multiple out-degrees, so multiple out-degree connected nodes can be processed at the same time.

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Therefore, its characteristics are:

1. Fast transaction speed. The local processing and parallel settlement realized by DAG can greatly improve the transaction speed.

2. Strong scalability, because each node can calculate without waiting for the synchronization of other nodes' data, making it easy for accounting nodes to respond to extensions. Therefore, DAG is very suitable for IoT projects, such as machine micropayments.

3. It is more difficult to do evil. Compared with the chain structure, it is much more difficult to make malicious modifications in DAG because DAG has many out-degrees and in-degrees. If you want to modify a node, then the corresponding in-degrees must be modified.

For chain networks, it is not that the processing power of the nodes is weak, but that the chain structure cannot perform parallel calculations. The time wasted is actually mainly waiting time: one is to initiate a transaction, which requires synchronizing the transaction with all nodes, and the other is when a node confirms it, it needs to be synchronized with the entire network.

The traditional blockchain single-chain transmission mode has a slow transmission speed and lacks the means to deal with forks. In order to solve this series of problems, blockchain scholars have taken a different approach and integrated DAG and blockchain, two originally incompatible technologies.

For example, the Dagger-Hashimoto algorithm released by Ethereum in June 2016, its core content is the DAG directed acyclic graph, and the Ethash algorithm currently used by Ethereum is improved through the Dagger-Hashimoto algorithm.

I believe that through the previous introduction, everyone has a general understanding of DAG technology. Now let’s return to the question at the beginning of this article. Why are there more and more DAG files, which makes mining impossible?

In fact, after using DAG technology, each newly generated block is linked to all previous blocks. The verification information of the new block contains the encrypted information of all previous blocks. This is the DAG file that everyone has heard of recently.

Simply put, the DAG file is the puzzle provided by the blockchain to miners, and the hash value of the next block is the answer. The person who solves the puzzle the fastest will receive the digital currency reward for this block.

Graphics card mining uses the computing power of the graphics card. In order to "decrypt" the information contained in the DAG file, the graphics card needs to load the DAG into its own video memory for calculation. Therefore, if you want to mine Ethereum, the graphics card's video memory must first be larger than the current DAG file size, otherwise mining will not be possible.

The size of Ethereum's DAG has increased from 1GB when the Dagger-Hashimoto algorithm was introduced in June 2016 to the current 2.7G at a rate of about 520MB per year. It is expected that the size of Ethereum's DAG will increase to 4G by the end of 2020. By then, graphics cards with less than 4G of video memory will no longer be able to be used to mine Ethereum.

But friends don't need to panic, after all, there is still some time to wait for the algorithm to be updated. And now there is mining technology through virtual cache. There is always a way out when the car reaches the mountain, and there are always more solutions than difficulties~