<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html > <head><title>Error handling</title> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <meta name="generator" content="TeX4ht (http://www.tug.org/tex4ht/)"> <meta name="originator" content="TeX4ht (http://www.tug.org/tex4ht/)"> <!-- html,3 --> <meta name="src" content="userhtml.tex"> <link rel="stylesheet" type="text/css" href="userhtml.css"> </head><body > <!--l. 3--><div class="crosslinks"><p class="noindent">[<a href="userhtmlsu80.html" >next</a>] [<a href="userhtmlse7.html" >prev</a>] [<a href="userhtmlse7.html#tailuserhtmlse7.html" >prev-tail</a>] [<a href="userhtmlsu71.html#tailuserhtmlse8.html">tail</a>] [<a href="userhtml.html#userhtmlsu76.html" >up</a>] </p></div> <h3 class="sectionHead"><span class="titlemark">8 </span> <a id="x86-1230008"></a>Error handling</h3> <!--l. 5--><p class="noindent" >The PSBLAS library error handling policy has been completely rewritten in version 2.0. The idea behind the design of this new error handling strategy is to keep error messages on a stack allowing the user to trace back up to the point where the first error message has been generated. Every routine in the PSBLAS-2.0 library has, as last non-optional argument, an integer <span class="obeylines-h"><span class="verb"><span class="cmtt-10">info</span></span></span> variable; whenever, inside the routine, an error is detected, this variable is set to a value corresponding to a specific error code. Then this error code is also pushed on the error stack and then either control is returned to the caller routine or the execution is aborted, depending on the users choice. At the time when the execution is aborted, an error message is printed on standard output with a level of verbosity than can be chosen by the user. If the execution is not aborted, then, the caller routine checks the value returned in the <span class="obeylines-h"><span class="verb"><span class="cmtt-10">info</span></span></span> variable and, if not zero, an error condition is raised. This process continues on all the levels of nested calls until the level where the user decides to abort the program execution. <!--l. 23--><p class="indent" > Figure <a href="#x86-1230259">9<!--tex4ht:ref: fig:routerr --></a> shows the layout of a generic <span class="obeylines-h"><span class="verb"><span class="cmtt-10">psb_foo</span></span></span> routine with respect to the PSBLAS-2.0 error handling policy. It is possible to see how, whenever an error condition is detected, the <span class="obeylines-h"><span class="verb"><span class="cmtt-10">info</span></span></span> variable is set to the corresponding error code which is, then, pushed on top of the stack by means of the <span class="obeylines-h"><span class="verb"><span class="cmtt-10">psb_errpush</span></span></span>. 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 <span class="obeylines-h"><span class="verb"><span class="cmtt-10">psb\_error</span></span></span> routine which prints the content of the error stack and aborts the program execution, according to the choice made by the user with <span class="obeylines-h"><span class="verb"><span class="cmtt-10">psb_set_erraction</span></span></span>. The default is to print the error and terminate the program, but the user may choose to handle the error explicitly. <!--l. 40--><p class="indent" > <hr class="figure"><div class="figure" > <a id="x86-1230259"></a> <div class="center" > <!--l. 73--><p class="noindent" > <div class="fbox"><div class="minipage"><!--l. 44--> <div class="lstlisting" id="listing-9"><span class="label"><a id="x86-123001r1"></a></span><span class="cmtt-9">subroutine</span><span class="cmtt-9"> </span><span class="cmtt-9">psb_foo</span><span class="cmtt-9">(</span><span class="cmtt-9">some</span><span class="cmtt-9"> </span><span class="cmtt-9">args</span><span class="cmtt-9">,</span><span class="cmtt-9"> </span><span class="cmtt-9">info</span><span class="cmtt-9">)</span><span class="cmtt-9"> </span><br /><span class="label"><a id="x86-123002r2"></a></span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9">...</span><span class="cmtt-9"> </span><br /><span class="label"><a id="x86-123003r3"></a></span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9">if</span><span class="cmtt-9">(</span><span class="cmtt-9">error</span><span class="cmtt-9"> </span><span class="cmtt-9">detected</span><span class="cmtt-9">)</span><span class="cmtt-9"> </span><span class="cmtt-9">then</span><span class="cmtt-9"> </span><br /><span class="label"><a id="x86-123004r4"></a></span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9">info</span><span class="cmtt-9">=</span><span class="cmtt-9">errcode1</span><span class="cmtt-9"> </span><br /><span class="label"><a id="x86-123005r5"></a></span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9">call</span><span class="cmtt-9"> </span><span class="cmtt-9">psb_errpush</span><span class="cmtt-9">(</span><span class="cmtt-9">’</span><span class="cmtt-9">psb_foo</span><span class="cmtt-9">’</span><span class="cmtt-9">,</span><span class="cmtt-9"> </span><span class="cmtt-9">errcode1</span><span class="cmtt-9">)</span><span class="cmtt-9"> </span><br /><span class="label"><a id="x86-123006r6"></a></span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9">goto</span><span class="cmtt-9"> </span><span class="cmtt-9">9999</span><span class="cmtt-9"> </span><br /><span class="label"><a id="x86-123007r7"></a></span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9">end</span><span class="cmtt-9"> </span><span class="cmtt-9">if</span><span class="cmtt-9"> </span><br /><span class="label"><a id="x86-123008r8"></a></span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9">...</span><span class="cmtt-9"> </span><br /><span class="label"><a id="x86-123009r9"></a></span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9">call</span><span class="cmtt-9"> </span><span class="cmtt-9">psb_bar</span><span class="cmtt-9">(</span><span class="cmtt-9">some</span><span class="cmtt-9"> </span><span class="cmtt-9">args</span><span class="cmtt-9">,</span><span class="cmtt-9"> </span><span class="cmtt-9">info</span><span class="cmtt-9">)</span><span class="cmtt-9"> </span><br /><span class="label"><a id="x86-123010r10"></a></span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9">if</span><span class="cmtt-9">(</span><span class="cmtt-9">info</span><span class="cmtt-9"> </span><span class="cmtt-9">.</span><span class="cmtt-9">ne</span><span class="cmtt-9">.</span><span class="cmtt-9"> </span><span class="cmtt-9">zero</span><span class="cmtt-9">)</span><span class="cmtt-9"> </span><span class="cmtt-9">then</span><span class="cmtt-9"> </span><br /><span class="label"><a id="x86-123011r11"></a></span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9">info</span><span class="cmtt-9">=</span><span class="cmtt-9">errcode2</span><span class="cmtt-9"> </span><br /><span class="label"><a id="x86-123012r12"></a></span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9">call</span><span class="cmtt-9"> </span><span class="cmtt-9">psb_errpush</span><span class="cmtt-9">(</span><span class="cmtt-9">’</span><span class="cmtt-9">psb_foo</span><span class="cmtt-9">’</span><span class="cmtt-9">,</span><span class="cmtt-9"> </span><span class="cmtt-9">errcode2</span><span class="cmtt-9">)</span><span class="cmtt-9"> </span><br /><span class="label"><a id="x86-123013r13"></a></span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9">goto</span><span class="cmtt-9"> </span><span class="cmtt-9">9999</span><span class="cmtt-9"> </span><br /><span class="label"><a id="x86-123014r14"></a></span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9">end</span><span class="cmtt-9"> </span><span class="cmtt-9">if</span><span class="cmtt-9"> </span><br /><span class="label"><a id="x86-123015r15"></a></span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9">...</span><span class="cmtt-9"> </span><br /><span class="label"><a id="x86-123016r16"></a></span><span class="cmtt-9">9999</span><span class="cmtt-9"> </span><span class="cmtt-9">continue</span><span class="cmtt-9"> </span><br /><span class="label"><a id="x86-123017r17"></a></span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9">if</span><span class="cmtt-9"> </span><span class="cmtt-9">(</span><span class="cmtt-9">err_act</span><span class="cmtt-9"> </span><span class="cmtt-9">.</span><span class="cmtt-9">eq</span><span class="cmtt-9">.</span><span class="cmtt-9"> </span><span class="cmtt-9">act_abort</span><span class="cmtt-9">)</span><span class="cmtt-9"> </span><span class="cmtt-9">then</span><span class="cmtt-9"> </span><br /><span class="label"><a id="x86-123018r18"></a></span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9">call</span><span class="cmtt-9"> </span><span class="cmtt-9">psb_error</span><span class="cmtt-9">(</span><span class="cmtt-9">icontxt</span><span class="cmtt-9">)</span><span class="cmtt-9"> </span><br /><span class="label"><a id="x86-123019r19"></a></span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9">return</span><span class="cmtt-9"> </span><br /><span class="label"><a id="x86-123020r20"></a></span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9">else</span><span class="cmtt-9"> </span><br /><span class="label"><a id="x86-123021r21"></a></span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9">return</span><span class="cmtt-9"> </span><br /><span class="label"><a id="x86-123022r22"></a></span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9"> </span><span class="cmtt-9">end</span><span class="cmtt-9"> </span><span class="cmtt-9">if</span><span class="cmtt-9"> </span><br /><span class="label"><a id="x86-123023r23"></a></span><span class="cmtt-9"> </span><br /><span class="label"><a id="x86-123024r24"></a></span><span class="cmtt-9">end</span><span class="cmtt-9"> </span><span class="cmtt-9">subroutine</span><span class="cmtt-9"> </span><span class="cmtt-9">psb_foo</span> </div> </div> </div> </div> <br /> <div class="caption" ><span class="id">Figure 9: </span><span class="content">The layout of a generic <span class="cmtt-10">psb</span><span class="cmtt-10">_foo </span>routine with respect to PSBLAS-2.0 error handling policy.</span></div><!--tex4ht:label?: x86-1230259 --> <!--l. 78--><p class="indent" > </div><hr class="endfigure"> <!--l. 83--><p class="indent" > Figure <a href="#x86-12302610">10<!--tex4ht:ref: fig:errormsg --></a> reports a sample error message generated by the PSBLAS-2.0 library. This error has been generated by the fact that the user has chosen the invalid “FOO” storage format to represent the sparse matrix. From this error message it is possible to see that the error has been detected inside the <span class="obeylines-h"><span class="verb"><span class="cmtt-10">psb_cest</span></span></span> subroutine called by <span class="obeylines-h"><span class="verb"><span class="cmtt-10">psb_spasb</span></span></span> ... by process 0 (i.e. the root process). <!--l. 91--><p class="indent" > <hr class="figure"><div class="figure" > <a id="x86-12302610"></a> <div class="center" > <!--l. 113--><p class="noindent" > <div class="fbox"><div class="minipage"><div class="verbatim" id="verbatim-101"> ==========================================================  <br />Process: 0.  PSBLAS Error (4010) in subroutine: df_sample  <br />Error from call to subroutine mat dist  <br />==========================================================  <br />Process: 0.  PSBLAS Error (4010) in subroutine: mat_distv  <br />Error from call to subroutine psb_spasb  <br />==========================================================  <br />Process: 0.  PSBLAS Error (4010) in subroutine: psb_spasb  <br />Error from call to subroutine psb_cest  <br />==========================================================  <br />Process: 0.  PSBLAS Error (136) in subroutine: psb_cest  <br />Format FOO is unknown  <br />==========================================================  <br />Aborting... </div> <!--l. 109--><p class="nopar" > </div> </div> </div> <br /> <div class="caption" ><span class="id">Figure 10: </span><span class="content">A sample PSBLAS-2.0 error message. Process 0 detected an error condition inside the psb_cest subroutine</span></div><!--tex4ht:label?: x86-12302610 --> <!--l. 119--><p class="indent" > </div><hr class="endfigure"> <div class="subsectionTOCS">  <span class="subsectionToc" >8.1 <a href="userhtmlsu74.html#x87-1240008.1">psb_errpush — Pushes an error code onto the error stack</a></span> <br />  <span class="subsectionToc" >8.2 <a href="userhtmlsu75.html#x88-1250008.2">psb_error — Prints the error stack content and aborts execution</a></span> <br />  <span class="subsectionToc" >8.3 <a href="userhtmlsu76.html#x89-1260008.3">psb_set_errverbosity — Sets the verbosity of error messages</a></span> <br />  <span class="subsectionToc" >8.4 <a href="userhtmlsu77.html#x90-1270008.4">psb_set_erraction — Set the type of action to be taken upon error condition</a></span> </div> <!--l. 1--><div class="crosslinks"><p class="noindent">[<a href="userhtmlsu80.html" >next</a>] [<a href="userhtmlse7.html" >prev</a>] [<a href="userhtmlse7.html#tailuserhtmlse7.html" >prev-tail</a>] [<a href="userhtmlse8.html" >front</a>] [<a href="userhtml.html#userhtmlsu76.html" >up</a>] </p></div> <!--l. 1--><p class="indent" > <a id="tailuserhtmlse8.html"></a> </body></html>