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<H1>EPSSetDimensions</H1>
Sets the number of eigenvalues to compute and the dimension of the subspace.
<H3><FONT COLOR="#883300">Synopsis</FONT></H3>
<PRE>
#include "slepceps.h"
PetscErrorCode EPSSetDimensions(EPS eps,PetscInt nev,PetscInt ncv,PetscInt mpd)
</PRE>
Logically Collective on <A HREF="../EPS/EPS.html#EPS">EPS</A>
<P>
<H3><FONT COLOR="#883300">Input Parameters</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>eps </B></TD><TD> - the eigensolver context
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>nev </B></TD><TD> - number of eigenvalues to compute
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>ncv </B></TD><TD> - the maximum dimension of the subspace to be used by the solver
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>mpd </B></TD><TD> - the maximum dimension allowed for the projected problem
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#883300">Options Database Keys</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-eps_nev <nev> </B></TD><TD> - Sets the number of eigenvalues
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-eps_ncv <ncv> </B></TD><TD> - Sets the dimension of the subspace
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-eps_mpd <mpd> </B></TD><TD> - Sets the maximum projected dimension
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#883300">Notes</FONT></H3>
Use PETSC_IGNORE to retain the previous value of any parameter.
<P>
Use PETSC_DECIDE for ncv and mpd to assign a reasonably good value, which is
dependent on the solution method.
<P>
The parameters ncv and mpd are intimately related, so that the user is advised
to set one of them at most. Normal usage is that
(a) in cases where nev is small, the user sets ncv (a reasonable default is 2*nev); and
(b) in cases where nev is large, the user sets mpd.
<P>
The value of ncv should always be between nev and (nev+mpd), typically
ncv=nev+mpd. If nev is not too large, mpd=nev is a reasonable choice, otherwise
a smaller value should be used.
<P>
When computing all eigenvalues in an interval, see <A HREF="../EPS/EPSSetInterval.html#EPSSetInterval">EPSSetInterval</A>(), the
meaning of nev changes. In that case, the number of eigenvalues in the
interval is not known a priori; the meaning of nev is then the number of
eigenvalues that are computed at a time when sweeping the interval from one
end to the other. The value of nev in this case may have an impact on overall
performance. The value of ncv should not be assigned in this case.
<P>
<P>
<H3><FONT COLOR="#883300">See Also</FONT></H3>
<A HREF="../EPS/EPSGetDimensions.html#EPSGetDimensions">EPSGetDimensions</A>(), <A HREF="../EPS/EPSSetInterval.html#EPSSetInterval">EPSSetInterval</A>()
<BR><P><B><FONT COLOR="#883300">Location: </FONT></B><A HREF="../../../src/eps/interface/opts.c.html#EPSSetDimensions">src/eps/interface/opts.c</A>
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