<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">I’ve begun working on implementing a projected time stepping method for solving y’ = f(y), where g(y(t)) is an invariant of the flow. Per a previous email exchange, it was suggested that I use TSSetPostStep to perform the projection routine, calling TSGetSolution obtain the current iterate, which will be corrected with the projection. However, I noticed two things:<div class=""><br class=""></div><div class="">1. The documentation for TSGetSolution says "This vector not changed until the solution at the next timestep has been calculated.” Does that mean that if I make a change to the solution in a PostStep function, it won’t be captured until the next step? What happens at the final time step?</div><div class=""><br class=""></div><div class="">2. The projection is nonlinear, requiring the use of a SNES. I had originally thought that I would create/configure/destroy the SNES within the main routine of the code, and pass this to the PostStep through a user data structure. However, the TSSetPostStep function seems to only take functions which are exclusively functions of the TS. Likewise, I would need to create a residual vector, r, for the SNESSetFunction. Is there a way to pass these data structures, so that they can be reused. or would they have to be created/destroyed within the PostStep function at each iterate? How costly would that be?<br class=""><div class=""><br class=""><div class=""><br class=""><div class="">
<span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; ">-gideon</span>
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