This error occurs when you select the Specify partitioning with chunk size (C) terminal option in the For Loop Iteration Parallelism dialog box and do not wire a chunk size to the chunk size ( C) terminal of the For Loop.

To correct this error, wire a value to the chunk size terminal or configure the For Loop to automatically partition the loop iterations. To configure the For Loop to automatically partition the loop iterations, right-click the For Loop, select Configure Iteration Parallelism from the shortcut menu to display the For Loop Iteration Parallelism dialog box, and select Automatically partition iterations in the Iteration partitioning schedule section.