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Added entrywise inversion and documentation for vec-vec operation
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<!--Converted with LaTeX2HTML 2018 (Released Feb 1, 2018) -->
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<HTML>
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<HEAD>
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<TITLE>Error handling</TITLE>
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<META NAME="description" CONTENT="Error handling">
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<TITLE>psb_nrm2 -- Global 2-norm reduction</TITLE>
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<META NAME="description" CONTENT="psb_nrm2 -- Global 2-norm reduction">
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HREF="node116.html">psb_rcv Receive</A>
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HREF="node118.html">psb_snd Send</A>
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HREF="node102.html">Parallel environment routines</A>
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HREF="node116.html">psb_amn Global</A>
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HREF="node1.html">Contents</A></B>
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<BR>
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<BR></DIV>
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<!--End of Navigation Panel-->
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<H1><A NAME="SECTION00090000000000000000">
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Error handling</A>
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</H1>
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<H2><A NAME="SECTION000815000000000000000">
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psb_nrm2 -- Global 2-norm reduction</A>
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</H2>
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<P>
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The PSBLAS library error handling policy has been completely rewritten
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in version 2.0. The idea behind the design of this new error handling
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strategy is to keep error messages on a stack allowing the user to
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trace back up to the point where the first error message has been
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||||
generated. Every routine in the PSBLAS-2.0 library has, as last
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||||
non-optional argument, an integer <code>info</code> variable; whenever,
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||||
inside the routine, an error is detected, this variable is set to a
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||||
value corresponding to a specific error code. Then this error code is
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||||
also pushed on the error stack and then either control is returned to
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||||
the caller routine or the execution is aborted, depending on the users
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||||
choice. At the time when the execution is aborted, an error message is
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printed on standard output with a level of verbosity than can be
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chosen by the user. If the execution is not aborted, then, the caller
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routine checks the value returned in the <code>info</code> variable and, if
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not zero, an error condition is raised. This process continues on all the
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levels of nested calls until the level where the user decides to abort
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the program execution.
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<P>
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Figure <A HREF="#fig:routerr">9</A> shows the layout of a generic <code>psb_foo</code>
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routine with respect to the PSBLAS-2.0 error handling policy. It is
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||||
possible to see how, whenever an error condition is detected, the
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||||
<code>info</code> variable is set to the corresponding error code which is,
|
||||
then, pushed on top of the stack by means of the
|
||||
<code>psb_errpush</code>. An error condition may be directly detected inside
|
||||
a routine or indirectly checking the error code returned returned by a
|
||||
called routine. Whenever an error is encountered, after it has been
|
||||
pushed on stack, the program execution skips to a point where the
|
||||
error condition is handled; the error condition is handled either by
|
||||
returning control to the caller routine or by calling the
|
||||
<code>psb\_error</code> routine which prints the content of the error stack
|
||||
and aborts the program execution, according to the choice made by the
|
||||
user with <code>psb_set_erraction</code>. The default is to print the error
|
||||
and terminate the program, but the user may choose to handle the error
|
||||
explicitly.
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||||
<P>
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||||
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||||
<DIV ALIGN="CENTER"><A NAME="fig:routerr"></A><A NAME="7481"></A>
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<TABLE>
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<CAPTION ALIGN="BOTTOM"><STRONG>Figure 9:</STRONG>
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The layout of a generic <TT>psb_foo</TT>
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routine with respect to PSBLAS-2.0 error handling policy.</CAPTION>
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<TR><TD>
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<BR>
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||||
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||||
<DIV ALIGN="CENTER">
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||||
<!-- MATH
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||||
$\fbox{\TheSbox}$
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-->
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||||
<SPAN CLASS="MATH"><IMG
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WIDTH="562" HEIGHT="482" ALIGN="MIDDLE" BORDER="0"
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SRC="img153.png"
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||||
ALT="\fbox{\TheSbox}"></SPAN>
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</DIV></TD></TR>
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</TABLE>
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</DIV>
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<P>
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Figure <A HREF="#fig:errormsg">10</A> reports a sample error message generated by
|
||||
the PSBLAS-2.0 library. This error has been generated by the fact that
|
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the user has chosen the invalid “FOO” storage format to represent
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the sparse matrix. From this error message it is possible to see that
|
||||
the error has been detected inside the <code>psb_cest</code> subroutine
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called by <code>psb_spasb</code> ... by process 0 (i.e. the root process).
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<P>
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<DIV ALIGN="CENTER"><A NAME="fig:errormsg"></A><A NAME="7482"></A>
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<TABLE>
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<CAPTION ALIGN="BOTTOM"><STRONG>Figure 10:</STRONG>
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A sample PSBLAS-2.0 error
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message. Process 0 detected an error condition inside the psb_cest subroutine</CAPTION>
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<TR><TD>
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<BR>
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||||
<DIV ALIGN="CENTER">
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||||
<!-- MATH
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$\fbox{\TheSbox}$
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-->
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||||
<SPAN CLASS="MATH"><IMG
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WIDTH="562" HEIGHT="482" ALIGN="MIDDLE" BORDER="0"
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SRC="img153.png"
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ALT="\fbox{\TheSbox}"></SPAN>
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</DIV></TD></TR>
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</TABLE>
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</DIV>
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<P>
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ifstarsubroutinesubroutinepsb_errpushPushes an error code onto the error
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stack
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<P>
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<BR>
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<IMG
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WIDTH="423" HEIGHT="16" ALIGN="BOTTOM" BORDER="0"
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SRC="img155.png"
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ALT="\begin{lstlisting}
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call psb_errpush(err_c, r_name, i_err, a_err)
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\end{lstlisting}">
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<BR>
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<PRE>
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call psb_nrm2(icontxt, dat, root)
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</PRE>
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<P>
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This subroutine implements a 2-norm value reduction
|
||||
operation based on the underlying communication library.
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<DL>
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||||
<DT><STRONG>Type:</STRONG></DT>
|
||||
<DD>Asynchronous.
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||||
<DD>Synchronous.
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||||
</DD>
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||||
<DT><STRONG><B>On Entry</B></STRONG></DT>
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<DD>
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</DD>
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||||
<DT><STRONG>err_c</STRONG></DT>
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||||
<DD>the error code
|
||||
<BR>
|
||||
Scope: <B>local</B>
|
||||
<BR>
|
||||
Type: <B>required</B>
|
||||
<BR>
|
||||
Intent: <B>in</B>.
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||||
<BR>
|
||||
Specified as: an integer.
|
||||
</DD>
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||||
<DT><STRONG>r_name</STRONG></DT>
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<DD>the soutine where the error has been caught.
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<BR>
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Scope: <B>local</B>
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||||
<BR>
|
||||
Type: <B>required</B>
|
||||
<BR>
|
||||
Intent: <B>in</B>.
|
||||
<BR>
|
||||
Specified as: a string.
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||||
<BR></DD>
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||||
<DT><STRONG>i_err</STRONG></DT>
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||||
<DD>addional info for error code
|
||||
<BR>
|
||||
Scope: <B>local</B>
|
||||
<BR>
|
||||
Type: <B>optional</B>
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||||
<BR>
|
||||
Specified as: an integer array
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<BR></DD>
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<DT><STRONG>a_err</STRONG></DT>
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||||
<DD>addional info for error code
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||||
<BR>
|
||||
Scope: <B>local</B>
|
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<BR>
|
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Type: <B>optional</B>
|
||||
<BR>
|
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Specified as: a string.
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<BR></DD>
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||||
</DL>
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||||
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<P>
|
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ifstarsubroutinesubroutinepsb_errorPrints the error stack content and aborts
|
||||
execution
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<P>
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||||
<BR>
|
||||
<IMG
|
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WIDTH="213" HEIGHT="16" ALIGN="BOTTOM" BORDER="0"
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SRC="img156.png"
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ALT="\begin{lstlisting}
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call psb_error(icontxt)
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\end{lstlisting}">
|
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<BR>
|
||||
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||||
<P>
|
||||
<DL>
|
||||
<DT><STRONG>Type:</STRONG></DT>
|
||||
<DD>Asynchronous.
|
||||
</DD>
|
||||
<DT><STRONG><B>On Entry</B></STRONG></DT>
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<DT><STRONG><B>On Entry </B></STRONG></DT>
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<DD>
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</DD>
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<DT><STRONG>icontxt</STRONG></DT>
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<DD>the communication context.
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<DD>the communication context identifying the virtual
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||||
parallel machine.
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<BR>
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||||
Scope: <B>global</B>
|
||||
Scope: <B>global</B>.
|
||||
<BR>
|
||||
Type: <B>optional</B>
|
||||
Type: <B>required</B>.
|
||||
<BR>
|
||||
Intent: <B>in</B>.
|
||||
<BR>
|
||||
Specified as: an integer.
|
||||
Specified as: an integer variable.
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</DD>
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<DT><STRONG>dat</STRONG></DT>
|
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<DD>The local contribution to the global minimum.
|
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<BR>
|
||||
Scope: <B>local</B>.
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||||
<BR>
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||||
Type: <B>required</B>.
|
||||
<BR>
|
||||
Intent: <B>inout</B>.
|
||||
<BR>
|
||||
Specified as: a real variable, which may be a
|
||||
scalar, or a rank 1 array. Kind, rank and size must agree on all processes.
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</DD>
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<DT><STRONG>root</STRONG></DT>
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<DD>Process to hold the final value, or <SPAN CLASS="MATH"><IMG
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WIDTH="24" HEIGHT="29" ALIGN="MIDDLE" BORDER="0"
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SRC="img88.png"
|
||||
ALT="$-1$"></SPAN> to make it available
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on all processes.
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||||
<BR>
|
||||
Scope: <B>global</B>.
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||||
<BR>
|
||||
Type: <B>optional</B>.
|
||||
<BR>
|
||||
Intent: <B>in</B>.
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||||
<BR>
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Specified as: an integer value <!-- MATH
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$-1<= root <= np-1$
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-->
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<SPAN CLASS="MATH"><IMG
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WIDTH="165" HEIGHT="29" ALIGN="MIDDLE" BORDER="0"
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SRC="img147.png"
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ALT="$-1<= root <= np-1$"></SPAN>, default -1.
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<BR></DD>
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</DL>
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<P>
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ifstarsubroutinesubroutinepsb_set_errverbositySets the verbosity of error
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messages.
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||||
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<P>
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||||
<BR>
|
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<IMG
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WIDTH="261" HEIGHT="16" ALIGN="BOTTOM" BORDER="0"
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SRC="img157.png"
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ALT="\begin{lstlisting}
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call psb_set_errverbosity(v)
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\end{lstlisting}">
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<BR>
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||||
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<P>
|
||||
<DL>
|
||||
<DT><STRONG>Type:</STRONG></DT>
|
||||
<DD>Asynchronous.
|
||||
</DD>
|
||||
<DT><STRONG><B>On Entry</B></STRONG></DT>
|
||||
<DT><STRONG><B>On Return</B></STRONG></DT>
|
||||
<DD>
|
||||
</DD>
|
||||
<DT><STRONG>v</STRONG></DT>
|
||||
<DD>the verbosity level
|
||||
<DT><STRONG>dat</STRONG></DT>
|
||||
<DD>On destination process(es), the result of the 2-norm reduction.
|
||||
<BR>
|
||||
Scope: <B>global</B>
|
||||
Scope: <B>global</B>.
|
||||
<BR>
|
||||
Type: <B>required</B>
|
||||
Type: <B>required</B>.
|
||||
<BR>
|
||||
Intent: <B>in</B>.
|
||||
Intent: <B>inout</B>.
|
||||
<BR>
|
||||
Specified as: an integer.
|
||||
Specified as: a real variable, which may be a
|
||||
scalar, or a rank 1 array.
|
||||
<BR>
|
||||
Kind, rank and size must agree on all processes.
|
||||
</DD>
|
||||
</DL>
|
||||
|
||||
<P>
|
||||
ifstarsubroutinesubroutinepsb_set_erractionSet the type of action to be
|
||||
taken upon error condition.
|
||||
<BIG CLASS="LARGE"><B>Notes</B></BIG>
|
||||
|
||||
<OL>
|
||||
<LI>This reduction is appropriate to compute the results of multiple
|
||||
(local) NRM2 operations at the same time.
|
||||
</LI>
|
||||
<LI>Denoting by <SPAN CLASS="MATH"><IMG
|
||||
WIDTH="32" HEIGHT="30" ALIGN="MIDDLE" BORDER="0"
|
||||
SRC="img148.png"
|
||||
ALT="$dat_i$"></SPAN> the value of the variable <SPAN CLASS="MATH"><IMG
|
||||
WIDTH="26" HEIGHT="15" ALIGN="BOTTOM" BORDER="0"
|
||||
SRC="img149.png"
|
||||
ALT="$dat$"></SPAN> on process
|
||||
<SPAN CLASS="MATH"><IMG
|
||||
WIDTH="9" HEIGHT="15" ALIGN="BOTTOM" BORDER="0"
|
||||
SRC="img4.png"
|
||||
ALT="$i$"></SPAN>, the output <SPAN CLASS="MATH"><IMG
|
||||
WIDTH="26" HEIGHT="14" ALIGN="BOTTOM" BORDER="0"
|
||||
SRC="img29.png"
|
||||
ALT="$res$"></SPAN> is equivalent to the computation of
|
||||
<BR><P></P>
|
||||
<DIV ALIGN="CENTER" CLASS="mathdisplay">
|
||||
<!-- MATH
|
||||
\begin{displaymath}
|
||||
res = \sqrt{\sum_i dat_i^2},
|
||||
\end{displaymath}
|
||||
-->
|
||||
|
||||
<P>
|
||||
<BR>
|
||||
<IMG
|
||||
WIDTH="289" HEIGHT="16" ALIGN="BOTTOM" BORDER="0"
|
||||
SRC="img158.png"
|
||||
ALT="\begin{lstlisting}
|
||||
call psb_set_erraction(err_act)
|
||||
\end{lstlisting}">
|
||||
<BR>
|
||||
|
||||
<P>
|
||||
<DL>
|
||||
<DT><STRONG>Type:</STRONG></DT>
|
||||
<DD>Asynchronous.
|
||||
</DD>
|
||||
<DT><STRONG><B>On Entry</B></STRONG></DT>
|
||||
<DD>
|
||||
</DD>
|
||||
<DT><STRONG>err_act</STRONG></DT>
|
||||
<DD>the type of action.
|
||||
<BR>
|
||||
Scope: <B>global</B>
|
||||
<BR>
|
||||
Type: <B>required</B>
|
||||
<BR>
|
||||
Intent: <B>in</B>.
|
||||
<BR>
|
||||
Specified as: an integer. Possible values: <code>psb_act_ret</code>,
|
||||
<code>psb_act_abort</code>.
|
||||
</DD>
|
||||
</DL>
|
||||
WIDTH="119" HEIGHT="55" BORDER="0"
|
||||
SRC="img150.png"
|
||||
ALT="\begin{displaymath}res = \sqrt{\sum_i dat_i^2},\end{displaymath}">
|
||||
</DIV>
|
||||
<BR CLEAR="ALL">
|
||||
<P></P>
|
||||
with care taken to avoid unnecessary overflow.
|
||||
</LI>
|
||||
<LI>The <code>dat</code> argument is both input and output, and its
|
||||
value may be changed even on processes different from the final
|
||||
result destination.
|
||||
</LI>
|
||||
</OL>
|
||||
|
||||
<P>
|
||||
|
||||
<DIV CLASS="navigation"><HR>
|
||||
<!--Navigation Panel-->
|
||||
<A NAME="tex2html1719"
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HREF="userhtml.html">
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HREF="node102.html">
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<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="up.png"></A>
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<B> Next:</B> <A NAME="tex2html1720"
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HREF="node118.html">Utilities</A>
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<B> Up:</B> <A NAME="tex2html1716"
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HREF="userhtml.html">userhtml</A>
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<B> Previous:</B> <A NAME="tex2html1710"
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HREF="node116.html">psb_rcv Receive</A>
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<B> <A NAME="tex2html1718"
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<B> Next:</B> <A NAME="tex2html1731"
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HREF="node118.html">psb_snd Send</A>
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<B> Up:</B> <A NAME="tex2html1727"
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HREF="node102.html">Parallel environment routines</A>
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<B> Previous:</B> <A NAME="tex2html1721"
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HREF="node116.html">psb_amn Global</A>
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<B> <A NAME="tex2html1729"
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HREF="node1.html">Contents</A></B> </DIV>
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