code: static final void localInit() {
          int p = probeGenerator.addAndGet(PROBE_INCREMENT);
          int probe = (p == 0) ? 1 : p; // skip 0
          long seed = mix64(seeder.getAndAdd(SEEDER_INCREMENT));
          Thread t = Thread.currentThread();
          U.putLong(t, SEED, seed);
          U.putInt(t, PROBE, probe);
      }
docs: Initialize Thread fields for the current thread.  Called only
  when Thread.threadLocalRandomProbe is zero, indicating that a
  thread local seed value needs to be generated. Note that even
  though the initialization is purely thread-local, we need to
  rely on (static) atomic generators to initialize the values.