工作量证明难度突然增加

Question

我正在模拟我使用initial difficulty set to (1/2)^16开始的私人比特币网络，但是在网络上大约20个挖掘块后，它增加到1并且从那时起一直保持不变。据我所知，从源代码开始，它应该在每个2016块之后增加，所以在仅仅20个块后它是如何增加的。

我的比特币实例中powLimit的更改。

strNetworkID = "regtest";
        consensus.nSubsidyHalvingInterval = 210000;
        consensus.nMajorityEnforceBlockUpgrade = 51;
        consensus.nMajorityRejectBlockOutdated = 75;
        consensus.nMajorityWindow = 100;
        consensus.powLimit = uint256S("0000ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff");
        consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks
        consensus.nPowTargetSpacing = 10 * 60;
        consensus.fPowAllowMinDifficultyBlocks = true;
        consensus.fPowNoRetargeting = false;