* supplier and accumulator.
   */
  static DoubleStream megaPrimitiveDoubleStream() {
    return DoubleStream.iterate(0.0, x -> x + 1.0).limit(MEGA_STREAM_COUNT).parallel();
  }

  /** Returns a stream containing half the values from {@link #megaPrimitiveDoubleStream}. */
  static DoubleStream megaPrimitiveDoubleStreamPart1() {

import static com.google.common.math.StatsTesting.TWO_VALUES_MIN;
import static com.google.common.math.StatsTesting.TWO_VALUES_SUM_OF_SQUARES_OF_DELTAS;
import static com.google.common.math.StatsTesting.megaPrimitiveDoubleStream;
import static com.google.common.math.StatsTesting.megaPrimitiveDoubleStreamPart1;
import static com.google.common.math.StatsTesting.megaPrimitiveDoubleStreamPart2;
import static com.google.common.truth.Truth.assertThat;