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<H1><A NAME="SECTION00080000000000000000"></A><A NAME="sec:userinterface"></A>
<BR>
User Interface
</H1>

<P>
The basic user interface of MLD2P4 consists of eight routines. The six
routines <code>init</code>, <code>set</code>,
<code>hierarchy_build</code>, <code>smoothers_build</code>,
<code>bld</code>, and <code>apply</code> encapsulate all the
functionalities for the setup and the application of any multi-level and one-level
preconditioner implemented in the package. 
The routine <code>free</code> deallocates the preconditioner data structure, while
<code>descr</code> prints a description of the preconditioner setup by the user.

<P>
All the routines are available as methods of the preconditioner object.
For each routine, the same user interface is overloaded with
respect to the real/ complex case and the single/double precision;
arguments with appropriate data types must be passed to the routine,
i.e.,

<UL>
<LI>the sparse matrix data structure, containing the matrix to be
  preconditioned, must be of type <code>psb_</code><I>x</I><code>spmat_type</code>
	with <I>x</I> = <code>s</code> for real single precision, <I>x</I> = <code>d</code>
	for real double precision, <I>x</I> = <code>c</code> for complex single precision,
	<I>x</I> = <code>z</code> for complex double precision;
</LI>
<LI>the preconditioner data structure must be of type
  <code>mld_</code><I>x</I><code>prec_type</code>, with <I>x</I> =    
  <code>s</code>, <code>d</code>, <code>c</code>, <code>z</code>, according to the sparse
  matrix data structure;
</LI>
<LI>the arrays containing the vectors <IMG
 WIDTH="14" HEIGHT="18" ALIGN="BOTTOM" BORDER="0"
 SRC="img14.png"
 ALT="$v$"> and <IMG
 WIDTH="18" HEIGHT="18" ALIGN="BOTTOM" BORDER="0"
 SRC="img15.png"
 ALT="$w$"> involved in
  the preconditioner application <IMG
 WIDTH="86" HEIGHT="21" ALIGN="BOTTOM" BORDER="0"
 SRC="img16.png"
 ALT="$w=M^{-1}v$"> must be of type   
  <code>psb_</code><I>x</I><code>vect_type</code> with <I>x</I> =    
  <code>s</code>, <code>d</code>, <code>c</code>, <code>z</code>, in a manner completely
  analogous to the sparse matrix type;
</LI>
<LI>real parameters defining the preconditioner must be declared
  according to the precision of the sparse matrix and preconditioner
  data structures (see Section&nbsp;<A HREF="node17.html#sec:precset">6.2</A>).
</LI>
</UL>
A description of each routine is given in the remainder of this section.

<P>

<P>
<BR><HR>
<!--Table of Child-Links-->
<A NAME="CHILD_LINKS"><STRONG>Subsections</STRONG></A>

<UL>
<LI><A NAME="tex2html257"
  HREF="node16.html">Subroutine init</A>
<LI><A NAME="tex2html258"
  HREF="node17.html">Subroutine set</A>
<LI><A NAME="tex2html259"
  HREF="node18.html">Subroutine build</A>
<LI><A NAME="tex2html260"
  HREF="node19.html">Subroutine hierarchy_build</A>
<LI><A NAME="tex2html261"
  HREF="node20.html">Subroutine smoothers_build</A>
<LI><A NAME="tex2html262"
  HREF="node21.html">Subroutine apply</A>
<LI><A NAME="tex2html263"
  HREF="node22.html">Subroutine free</A>
<LI><A NAME="tex2html264"
  HREF="node23.html">Subroutine descr</A>
</UL>
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