:term:`REPL_OTF <REPL_OTF (DETCI)>`
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      Do string replacements on the fly in DETCI? Can save a gigantic amount of memory (especially for truncated CI's) but is somewhat flaky and hasn't been tested for a while. It may work only works for certain classes of RAS calculations. The current code is very slow with this option turned on. 

      * **Type**: :ref:`boolean <op_c_boolean>`
      * **Default**: false