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<font face="serif">Guys -- while the direct linear solver does not
have to have a diagonally dominant matrix to guarantee convergence
(it does the row interchanges to obviate the need for that
requirement) the iterative linear solver needs to have a
diagonally dominant matrix "A" to <i>guarantee</i> convergence.
<br>
<br>
Here is how I constructed my matrix A in my Fortran code to make
sure I was close to diagonal dominance.<br>
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<font face="Courier New, Courier, monospace">do i = 1, DIM <br>
do j = 1, DIM <br>
call random_number(ranval)<br>
if ( i .ne. j) then<br>
matrixa(j,i) = ranval <br>
else<br>
matrixa(j,i) = 2.0 * ranval * DIM<br>
endif<br>
enddo<br>
enddo</font><br>
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<pre class="moz-signature" cols="72">--
Andrew J. Pounds, Ph.D. (<a class="moz-txt-link-abbreviated" href="mailto:pounds_aj@mercer.edu">pounds_aj@mercer.edu</a>)
Professor of Chemistry and Computer Science
Mercer University, Macon, GA 31207 (478) 301-5627
<a class="moz-txt-link-freetext" href="http://faculty.mercer.edu/pounds_aj">http://faculty.mercer.edu/pounds_aj</a>
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