The Reverse Communication Interface

  The basic reverse communication loop for the complex driver is exactly the same as those used for the symmetric driver except that dsaupd is replaced by znaupd. (Figure A.1.) Actions to be taken within the loop vary from one driver to the other. Some drivers may take only one or two actions listed in Figure A.1. Each action corresponds to an ido value returned from the call to znaupd. These actions involve matrix vector operations such as and The matrix vector operation must be performed correctly on the correct portion of the work array workd (either workd(ipntr(1)) or workd(ipntr(3)).) The output should also be returned in the correct portion of workd (either workd(ipntr(2)) or workd(ipntr(1))) before the loop goes back to the next call to znaupd. The matrix-vector operations required of each driver are listed in detail below.