Ok thank you very much<br><br>
<div><span class="gmail_quote">On 4/9/07, <b class="gmail_sendername">Barry Smith</b> <<a href="mailto:bsmith@mcs.anl.gov">bsmith@mcs.anl.gov</a>> wrote:</span>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid"><br><br>On Mon, 9 Apr 2007, Ben Tay wrote:<br><br>> Hi,<br>><br>> I am solving a poisson eqn and using hypre as a preconditioner has greatly
<br>> increased the speed. I am trying to do some more tuning and I have some<br>> questions:<br>><br>> 1. Is boomerAMG the only option?<br><br>Yes, but all will suck on the poisson compared to boomeramg, so stick to
<br>boomer<br><br>What are the other hypre conditioners<br>> available? Is there any documentation somewhere?<br><br>Run with -help and check the hypre users manual<br><br>>Is hypre just a<br>> preconditioner or can it be a solver as well?
<br><br>Run with -ksp_type richardson to use it as a "solver"<br>><br>> 2. what does the preonly in ksp_type mean? Is the eqns solved?<br><br> It means apply the preconditioner ONCE, unless the preconditioner is
<br>a direct solver it does not solve the equations. Richardson means run<br>some number of iterations of the preconditioner and can solve the equations<br><br>><br>> 3. why can't I use bcgs or bicg with hypre?
<br><br> hypre doesn't support applying the transpose of the preconditioner that<br>bcgs and bicg need?<br><br><br>> Also, can cg be used for<br>> non-symmetric matrix. It seems to work.<br><br>Sometimes it works, but it is dangerous and not worth risking.
<br><br> Barry<br><br>><br>> Thank you very much.<br>><br>> Regards.<br>><br><br></blockquote></div><br>