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bbpresolve  Compute preliminary solution for A*X=B.
   S=bbpresolve(A,B,REG) takes a black-box operator, A, and a
   column-vector, B, and computes a splitting suitable for computing a
   solution using bbsolve (with REG=false) or a regularized solution
   using bbregsolve (with REG=true).

   S=bbpresolve(A,B,OPT) tunes the computation according to the
   parameters specified by OPT. See bbsolveopt for a list of options.

   See also bbsolve, bbregsolve, bbsolveopt.