substreamBlockSize

the size of the sub-stream tape block reserved for each member: member k's simulation streams start at sub-stream index k times this value, so members draw from non-overlapping tape regions regardless of scheduling. Sub-stream positioning is a constant-time jump, so a generous default costs nothing. A member consumes roughly (its evaluations times its replications per evaluation) sub-streams; the default of one million comfortably exceeds realistic runs, and the pooled evaluator factory logs a warning if a member overruns its block.