Calibrator.java

import java.util.List;
import java.util.ArrayList;
import java.util.Random;

import java.time.Instant;
import java.time.temporal.ChronoUnit;
import org.bitcoinj.base.Difficulty;
import org.bitcoinj.base.Sha256Hash;
import org.bitcoinj.core.Block;
import org.bitcoinj.core.Transaction;

public class Calibrator {
    public static void main(String [] args) throws Exception {
	if (args.length != 1) {
	    System.err.println("Usage: java Calibrator hex_target");
	    System.exit(-1);
	} else {
	    System.out.println("Patience please, this may take a while");
	}
	long target = Long.parseLong(args[0], 16);


	Random random = new Random();
	int n = 100;
	long startTime = System.currentTimeMillis();
	for (int r = 0; r < n; r++) {
	    int version = 1;
	    byte[] bytes1 = new byte[32];
	    random.nextBytes(bytes1);
	    Sha256Hash prevBlockHash = Sha256Hash.wrap(bytes1);
	    byte[] bytes2 = new byte[32];
	    random.nextBytes(bytes2);
	    Sha256Hash merkleRootHash = Sha256Hash.wrap(bytes2);
	    Instant time = Instant.now().truncatedTo(ChronoUnit.SECONDS);
	    Difficulty difficulty = Difficulty.ofCompact(target);
	    long nonce = 0;
	    List<Transaction> txns = null;
	    Block b = new Block(version, prevBlockHash, merkleRootHash, time, difficulty, nonce, txns);

	    while (!difficulty.isMetByWork(b.getHash())) {
		b.setNonce(++nonce);
	    }

	    System.out.println("" + (r+1) + "% complete");
	}
	long endTime = System.currentTimeMillis();

	System.out.println("Throughput (blocks/s) for target " + args[0] + ": " + n*1000f/(endTime-startTime));
	System.out.println("Latency (ms/block)    for target " + args[0] + ": " + 1f*(endTime-startTime)/n);
    }
}