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    <p>How can I be sure they are indeed used? Can I print this
      information in some log file? <br>
    </p>
    <p>Thanks in advance<br>
    </p>
    <p>Myriam<br>
    </p>
    <br>
    <div class="moz-cite-prefix">Le 03/25/19 à 18:24, Matthew Knepley a
      écrit :<br>
    </div>
    <blockquote type="cite"
cite="mid:CAMYG4G==LGGbnuaAzzx8opQWwUck8agtchbLLcfMnPch74Pefg@mail.gmail.com">
      <meta http-equiv="content-type" content="text/html; charset=utf-8">
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        <div dir="ltr">On Mon, Mar 25, 2019 at 10:54 AM Myriam
          Peyrounette via petsc-users <<a
            href="mailto:petsc-users@mcs.anl.gov" moz-do-not-send="true">petsc-users@mcs.anl.gov</a>>
          wrote:<br>
        </div>
        <div class="gmail_quote">
          <blockquote class="gmail_quote" style="margin:0px 0px 0px
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            <div bgcolor="#FFFFFF">
              <p>Hi,</p>
              <p>thanks for the explanations. I tried the last PETSc
                version (commit
                fbc5705bc518d02a4999f188aad4ccff5f754cbf), which
                includes the patch you talked about. But the memory
                scaling shows no improvement (see scaling attached),
                even when using the "scalable" options :(</p>
              <p>I had a look at the PETSc functions
                MatPtAPNumeric_MPIAIJ_MPIAIJ and
                MatPtAPSymbolic_MPIAIJ_MPIAIJ (especially at the
                differences before and after the first "bad" commit),
                but I can't find what induced this memory issue.</p>
            </div>
          </blockquote>
          <div>Are you sure that the option was used? It just looks
            suspicious to me that they use exactly the same amount of
            memory. It should be different, even if it does not solve
            the problem.</div>
          <div><br>
          </div>
          <div>   Thanks,</div>
          <div><br>
          </div>
          <div>     Matt </div>
          <blockquote class="gmail_quote" style="margin:0px 0px 0px
            0.8ex;border-left:1px solid
            rgb(204,204,204);padding-left:1ex">
            <div bgcolor="#FFFFFF">
              <p>Myriam<br>
              </p>
              <p><br>
              </p>
              <p><br>
              </p>
              <br>
              <div class="gmail-m_7299408251829905453moz-cite-prefix">Le
                03/20/19 à 17:38, Fande Kong a écrit :<br>
              </div>
              <blockquote type="cite">
                <div dir="ltr">
                  <div dir="ltr">
                    <div dir="ltr">
                      <div dir="ltr">
                        <div dir="ltr">
                          <div dir="ltr">
                            <div>Hi Myriam,</div>
                            <div><br>
                            </div>
                            <div>There are three algorithms in PETSc to
                              do PtAP ( const char          *algTypes[3]
                              = {"scalable","nonscalable","hypre"};),
                              and can be specified using the petsc
                              options: -matptap_via xxxx.</div>
                            <div><br>
                            </div>
                            <div>(1) -matptap_via hypre: This call the
                              hypre package to do the PtAP trough an
                              all-at-once triple product. In our
                              experiences, it is the most memory
                              efficient, but could be slow.</div>
                            <div><br>
                            </div>
                            <div>(2)  -matptap_via scalable: This
                              involves a row-wise algorithm plus an
                              outer product.  This will use more memory
                              than hypre, but way faster. This used to
                              have a bug that could take all your
                              memory, and I have a fix at <a
href="https://bitbucket.org/petsc/petsc/pull-requests/1452/mpiptap-enable-large-scale-simulations/diff"
                                target="_blank" moz-do-not-send="true">https://bitbucket.org/petsc/petsc/pull-requests/1452/mpiptap-enable-large-scale-simulations/diff</a>. 
                              When using this option, we may want to
                              have extra options such as 
                               -inner_offdiag_matmatmult_via scalable
                              -inner_diag_matmatmult_via scalable  to
                              select inner scalable algorithms.</div>
                            <div><br>
                            </div>
                            <div>(3)  -matptap_via nonscalable:  Suppose
                              to be even faster, but use more memory. It
                              does dense matrix operations.</div>
                            <div><br>
                            </div>
                            <div><br>
                            </div>
                            <div>Thanks,</div>
                            <div><br>
                            </div>
                            <div>Fande Kong</div>
                            <div><br>
                            </div>
                            <div><br>
                            </div>
                            <div><br>
                            </div>
                            <br>
                            <div class="gmail_quote">
                              <div dir="ltr" class="gmail_attr">On Wed,
                                Mar 20, 2019 at 10:06 AM Myriam
                                Peyrounette via petsc-users <<a
                                  href="mailto:petsc-users@mcs.anl.gov"
                                  target="_blank" moz-do-not-send="true">petsc-users@mcs.anl.gov</a>>
                                wrote:<br>
                              </div>
                              <blockquote class="gmail_quote"
                                style="margin:0px 0px 0px
                                0.8ex;border-left:1px solid
                                rgb(204,204,204);padding-left:1ex">
                                <div bgcolor="#FFFFFF">
                                  <p>More precisely: something happens
                                    when upgrading the functions
                                    MatPtAPNumeric_MPIAIJ_MPIAIJ and/or
                                    MatPtAPSymbolic_MPIAIJ_MPIAIJ. <br>
                                  </p>
                                  <p>Unfortunately, there are a lot of
                                    differences between the old and new
                                    versions of these functions. I keep
                                    investigating but if you have any
                                    idea, please let me know.</p>
                                  <p>Best,<br>
                                  </p>
                                  <p>Myriam<br>
                                  </p>
                                  <br>
                                  <div
class="gmail-m_7299408251829905453gmail-m_7961152398334556293moz-cite-prefix">Le
                                    03/20/19 à 13:48, Myriam Peyrounette
                                    a écrit :<br>
                                  </div>
                                  <blockquote type="cite">
                                    <p>Hi all,</p>
                                    <p>I used git bisect to determine
                                      when the memory need increased. I
                                      found that the first "bad" commit
                                      is  
                                      aa690a28a7284adb519c28cb44eae20a2c131c85.</p>
                                    <p>Barry was right, this commit
                                      seems to be about an evolution of
                                      <span
class="gmail-m_7299408251829905453gmail-m_7961152398334556293blob-code-inner"><span
class="gmail-m_7299408251829905453gmail-m_7961152398334556293pl-en
                                          gmail-m_7299408251829905453gmail-m_7961152398334556293x
gmail-m_7299408251829905453gmail-m_7961152398334556293x-first
                                          gmail-m_7299408251829905453gmail-m_7961152398334556293x-last">MatPtAPSymbolic_MPIAIJ_MPIAIJ.
                                          You mentioned the option
                                          "-matptap_via scalable" but I
                                          can't find any information
                                          about it. Can you tell me
                                          more?</span></span></p>
                                    <p><span
class="gmail-m_7299408251829905453gmail-m_7961152398334556293blob-code-inner"><span
class="gmail-m_7299408251829905453gmail-m_7961152398334556293pl-en
                                          gmail-m_7299408251829905453gmail-m_7961152398334556293x
gmail-m_7299408251829905453gmail-m_7961152398334556293x-first
                                          gmail-m_7299408251829905453gmail-m_7961152398334556293x-last">Thanks</span></span></p>
                                    <p><span
class="gmail-m_7299408251829905453gmail-m_7961152398334556293blob-code-inner"><span
class="gmail-m_7299408251829905453gmail-m_7961152398334556293pl-en
                                          gmail-m_7299408251829905453gmail-m_7961152398334556293x
gmail-m_7299408251829905453gmail-m_7961152398334556293x-first
                                          gmail-m_7299408251829905453gmail-m_7961152398334556293x-last">Myriam</span></span></p>
                                    <p><span
class="gmail-m_7299408251829905453gmail-m_7961152398334556293blob-code-inner"><span
class="gmail-m_7299408251829905453gmail-m_7961152398334556293pl-en
                                          gmail-m_7299408251829905453gmail-m_7961152398334556293x
gmail-m_7299408251829905453gmail-m_7961152398334556293x-first
                                          gmail-m_7299408251829905453gmail-m_7961152398334556293x-last"></span></span></p>
                                    <br>
                                    <div
class="gmail-m_7299408251829905453gmail-m_7961152398334556293moz-cite-prefix">Le
                                      03/11/19 à 14:40, Mark Adams a
                                      écrit :<br>
                                    </div>
                                    <blockquote type="cite">
                                      <div dir="ltr">Is there a
                                        difference in memory usage on
                                        your tiny problem? I assume no.
                                        <div><br>
                                        </div>
                                        <div>I don't see anything that
                                          could come from GAMG other
                                          than the RAP stuff that you
                                          have discussed already.</div>
                                      </div>
                                      <br>
                                      <div class="gmail_quote">
                                        <div dir="ltr"
                                          class="gmail_attr">On Mon, Mar
                                          11, 2019 at 9:32 AM Myriam
                                          Peyrounette <<a
                                            href="mailto:myriam.peyrounette@idris.fr"
                                            target="_blank"
                                            moz-do-not-send="true">myriam.peyrounette@idris.fr</a>>
                                          wrote:<br>
                                        </div>
                                        <blockquote class="gmail_quote"
                                          style="margin:0px 0px 0px
                                          0.8ex;border-left:1px solid
                                          rgb(204,204,204);padding-left:1ex">
                                          <div bgcolor="#FFFFFF">
                                            <p>The code I am using here
                                              is the example 42 of PETSc
                                              (<a
class="gmail-m_7299408251829905453gmail-m_7961152398334556293gmail-m_4941328961016005032moz-txt-link-freetext"
href="https://www.mcs.anl.gov/petsc/petsc-3.9/src/ksp/ksp/examples/tutorials/ex42.c.html"
                                                target="_blank"
                                                moz-do-not-send="true">https://www.mcs.anl.gov/petsc/petsc-3.9/src/ksp/ksp/examples/tutorials/ex42.c.html</a>).
                                              Indeed it solves the
                                              Stokes equation. I thought
                                              it was a good idea to use
                                              an example you might know
                                              (and didn't find any that
                                              uses GAMG functions). I
                                              just changed the PCMG
                                              setup so that the memory
                                              problem appears. And it
                                              appears when adding
                                              PCGAMG.</p>
                                            <p>I don't care about the
                                              performance or even the
                                              result rightness here, but
                                              only about the difference
                                              in memory use between 3.6
                                              and 3.10. Do you think
                                              finding a more adapted
                                              script would help?<br>
                                            </p>
                                            <p>I used the threshold of
                                              0.1 only once, at the
                                              beginning, to test its
                                              influence. I used the
                                              default threshold (of 0, I
                                              guess) for all the other
                                              runs.</p>
                                            <p>Myriam<br>
                                            </p>
                                            <br>
                                            <div
class="gmail-m_7299408251829905453gmail-m_7961152398334556293gmail-m_4941328961016005032moz-cite-prefix">Le
                                              03/11/19 à 13:52, Mark
                                              Adams a écrit :<br>
                                            </div>
                                            <blockquote type="cite">
                                              <div dir="ltr">
                                                <div dir="ltr">In
                                                  looking at this larger
                                                  scale run ...
                                                  <div><br>
                                                  </div>
                                                  <div>* Your eigen
                                                    estimates are much
                                                    lower than your tiny
                                                    test problem.  But
                                                    this is Stokes
                                                    apparently and it
                                                    should not work
                                                    anyway. Maybe you
                                                    have a small time
                                                    step that adds a lot
                                                    of mass that brings
                                                    the eigen estimates
                                                    down. And your min
                                                    eigenvalue (not
                                                    used) is positive. I
                                                    would expect
                                                    negative for Stokes
                                                    ...</div>
                                                  <div><br>
                                                  </div>
                                                  <div>* You seem to be
                                                    setting a threshold
                                                    value of 0.1 -- that
                                                    is very high</div>
                                                  <div><br>
                                                  </div>
                                                  <div>* v3.6 says
                                                    "using nonzero
                                                    initial guess" but
                                                    this is not in
                                                    v3.10. Maybe we just
                                                    stopped printing
                                                    that.</div>
                                                  <div><br>
                                                  </div>
                                                  <div>* There were some
                                                    changes to coasening
                                                    parameters in going
                                                    from v3.6 but it
                                                    does not look like
                                                    your problem was
                                                    effected. (The
                                                    coarsening algo is
                                                    non-deterministic by
                                                    default and you can
                                                    see small difference
                                                    on different runs)</div>
                                                  <div><br>
                                                  </div>
                                                  <div>* We may have
                                                    also added a "noisy"
                                                    RHS for eigen
                                                    estimates by default
                                                    from v3.6.</div>
                                                  <div><br>
                                                  </div>
                                                  <div>* And for
                                                    non-symetric
                                                    problems you can try
-pc_gamg_agg_nsmooths 0, but again GAMG is not built for Stokes anyway.</div>
                                                  <div><br>
                                                  </div>
                                                </div>
                                              </div>
                                              <br>
                                              <div class="gmail_quote">
                                                <div dir="ltr"
                                                  class="gmail_attr">On
                                                  Tue, Mar 5, 2019 at
                                                  11:53 AM Myriam
                                                  Peyrounette <<a
                                                    href="mailto:myriam.peyrounette@idris.fr"
                                                    target="_blank"
                                                    moz-do-not-send="true">myriam.peyrounette@idris.fr</a>>
                                                  wrote:<br>
                                                </div>
                                                <blockquote
                                                  class="gmail_quote"
                                                  style="margin:0px 0px
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                                                  solid
                                                  rgb(204,204,204);padding-left:1ex">
                                                  <div bgcolor="#FFFFFF">
                                                    <p>I used PCView to
                                                      display the size
                                                      of the linear
                                                      system in each
                                                      level of the MG.
                                                      You'll find the
                                                      outputs attached
                                                      to this mail (zip
                                                      file) for both the
                                                      default threshold
                                                      value and a value
                                                      of 0.1, and for
                                                      both 3.6 and 3.10
                                                      PETSc versions. <br>
                                                    </p>
                                                    <p>For convenience,
                                                      I summarized the
                                                      information in a
                                                      graph, also
                                                      attached (png
                                                      file).</p>
                                                    <p>As you can see,
                                                      there are slight
                                                      differences
                                                      between the two
                                                      versions but none
                                                      is critical, in my
                                                      opinion. Do you
                                                      see anything
                                                      suspicious in the
                                                      outputs?</p>
                                                    <p>+ I can't find
                                                      the default
                                                      threshold value.
                                                      Do you know where
                                                      I can find it?<br>
                                                    </p>
                                                    <p>Thanks for the
                                                      follow-up</p>
                                                    <p>Myriam<br>
                                                    </p>
                                                    <br>
                                                    <div
class="gmail-m_7299408251829905453gmail-m_7961152398334556293gmail-m_4941328961016005032gmail-m_4553173887686987135moz-cite-prefix">Le
                                                      03/05/19 à 14:06,
                                                      Matthew Knepley a
                                                      écrit :<br>
                                                    </div>
                                                    <blockquote
                                                      type="cite">
                                                      <div dir="ltr">
                                                        <div dir="ltr">On
                                                          Tue, Mar 5,
                                                          2019 at 7:14
                                                          AM Myriam
                                                          Peyrounette
                                                          <<a
                                                          href="mailto:myriam.peyrounette@idris.fr"
target="_blank" moz-do-not-send="true">myriam.peyrounette@idris.fr</a>>
                                                          wrote:<br>
                                                        </div>
                                                        <div
                                                          class="gmail_quote">
                                                          <blockquote
                                                          class="gmail_quote"
style="margin:0px 0px 0px 0.8ex;border-left:1px solid
                                                          rgb(204,204,204);padding-left:1ex">
                                                          <div
                                                          bgcolor="#FFFFFF">
                                                          <p>Hi Matt,</p>
                                                          <p>I plotted
                                                          the memory
                                                          scalings using
                                                          different
                                                          threshold
                                                          values. The
                                                          two scalings
                                                          are slightly
                                                          translated
                                                          (from -22 to
                                                          -88 mB) but
                                                          this gain is
                                                          neglectable.
                                                          The
                                                          3.6-scaling
                                                          keeps being
                                                          robust while
                                                          the
                                                          3.10-scaling
                                                          deteriorates.</p>
                                                          <p>Do you have
                                                          any other
                                                          suggestion?</p>
                                                          </div>
                                                          </blockquote>
                                                          <div>Mark,
                                                          what is the
                                                          option she can
                                                          give to output
                                                          all the GAMG
                                                          data?</div>
                                                          <div><br>
                                                          </div>
                                                          <div>Also, run
                                                          using
                                                          -ksp_view.
                                                          GAMG will
                                                          report all the
                                                          sizes of its
                                                          grids, so it
                                                          should be easy
                                                          to see</div>
                                                          <div>if the
                                                          coarse grid
                                                          sizes are
                                                          increasing,
                                                          and also what
                                                          the effect of
                                                          the threshold
                                                          value is.</div>
                                                          <div><br>
                                                          </div>
                                                          <div>  Thanks,</div>
                                                          <div><br>
                                                          </div>
                                                          <div>   
                                                           Matt <br>
                                                          </div>
                                                          <blockquote
                                                          class="gmail_quote"
style="margin:0px 0px 0px 0.8ex;border-left:1px solid
                                                          rgb(204,204,204);padding-left:1ex">
                                                          <div
                                                          bgcolor="#FFFFFF">
                                                          <p>Thanks<br>
                                                          </p>
                                                          Myriam <br>
                                                          <br>
                                                          <div
class="gmail-m_7299408251829905453gmail-m_7961152398334556293gmail-m_4941328961016005032gmail-m_4553173887686987135gmail-m_-3242500023102749998moz-cite-prefix">Le
                                                          03/02/19 à
                                                          02:27, Matthew
                                                          Knepley a
                                                          écrit :<br>
                                                          </div>
                                                          <blockquote
                                                          type="cite">
                                                          <div dir="ltr">
                                                          <div dir="ltr">
                                                          <div dir="ltr">On
                                                          Fri, Mar 1,
                                                          2019 at 10:53
                                                          AM Myriam
                                                          Peyrounette
                                                          via
                                                          petsc-users
                                                          <<a
                                                          href="mailto:petsc-users@mcs.anl.gov"
target="_blank" moz-do-not-send="true">petsc-users@mcs.anl.gov</a>>
                                                          wrote:<br>
                                                          </div>
                                                          <div
                                                          class="gmail_quote">
                                                          <blockquote
                                                          class="gmail_quote"
style="margin:0px 0px 0px 0.8ex;border-left:1px solid
                                                          rgb(204,204,204);padding-left:1ex">Hi,<br>
                                                          <br>
                                                          I used to run
                                                          my code with
                                                          PETSc 3.6.
                                                          Since I
                                                          upgraded the
                                                          PETSc version<br>
                                                          to 3.10, this
                                                          code has a bad
                                                          memory
                                                          scaling.<br>
                                                          <br>
                                                          To report this
                                                          issue, I took
                                                          the PETSc
                                                          script ex42.c
                                                          and slightly<br>
                                                          modified it so
                                                          that the KSP
                                                          and PC
                                                          configurations
                                                          are the same
                                                          as in my<br>
                                                          code. In
                                                          particular, I
                                                          use a
                                                          "personnalised"
                                                          multi-grid
                                                          method. The<br>
                                                          modifications
                                                          are indicated
                                                          by the keyword
                                                          "TopBridge" in
                                                          the attached<br>
                                                          scripts.<br>
                                                          <br>
                                                          To plot the
                                                          memory (weak)
                                                          scaling, I ran
                                                          four
                                                          calculations
                                                          for each<br>
                                                          script with
                                                          increasing
                                                          problem sizes
                                                          and
                                                          computations
                                                          cores:<br>
                                                          <br>
                                                          1. 100,000
                                                          elts on 4
                                                          cores<br>
                                                          2. 1 million
                                                          elts on 40
                                                          cores<br>
                                                          3. 10 millions
                                                          elts on 400
                                                          cores<br>
                                                          4. 100
                                                          millions elts
                                                          on 4,000 cores<br>
                                                          <br>
                                                          The resulting
                                                          graph is also
                                                          attached. The
                                                          scaling using
                                                          PETSc 3.10<br>
                                                          clearly
                                                          deteriorates
                                                          for large
                                                          cases, while
                                                          the one using
                                                          PETSc 3.6 is<br>
                                                          robust.<br>
                                                          <br>
                                                          After a few
                                                          tests, I found
                                                          that the
                                                          scaling is
                                                          mostly
                                                          sensitive to
                                                          the<br>
                                                          use of the AMG
                                                          method for the
                                                          coarse grid
                                                          (line 1780 in<br>
main_ex42_petsc36.cc). In particular, the performance strongly<br>
                                                          deteriorates
                                                          when
                                                          commenting
                                                          lines 1777 to
                                                          1790 (in
                                                          main_ex42_petsc36.cc).<br>
                                                          <br>
                                                          Do you have
                                                          any idea of
                                                          what changed
                                                          between
                                                          version 3.6
                                                          and version<br>
                                                          3.10 that may
                                                          imply such
                                                          degradation?<br>
                                                          </blockquote>
                                                          <div><br>
                                                          </div>
                                                          <div>I believe
                                                          the default
                                                          values for
                                                          PCGAMG changed
                                                          between
                                                          versions. It
                                                          sounds like
                                                          the coarsening
                                                          rate</div>
                                                          <div>is not
                                                          great enough,
                                                          so that these
                                                          grids are too
                                                          large. This
                                                          can be set
                                                          using:</div>
                                                          <div><br>
                                                          </div>
                                                          <div>  <a
href="https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/PC/PCGAMGSetThreshold.html"
target="_blank" moz-do-not-send="true">https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/PC/PCGAMGSetThreshold.html</a></div>
                                                          <div><br>
                                                          </div>
                                                          <div>There is
                                                          some
                                                          explanation of
                                                          this effect on
                                                          that page. Let
                                                          us know if
                                                          setting this
                                                          does not
                                                          correct the
                                                          situation.</div>
                                                          <div><br>
                                                          </div>
                                                          <div>  Thanks,</div>
                                                          <div><br>
                                                          </div>
                                                          <div>     Matt</div>
                                                          <div> </div>
                                                          <blockquote
                                                          class="gmail_quote"
style="margin:0px 0px 0px 0.8ex;border-left:1px solid
                                                          rgb(204,204,204);padding-left:1ex">
                                                          Let me know if
                                                          you need
                                                          further
                                                          information.<br>
                                                          <br>
                                                          Best,<br>
                                                          <br>
                                                          Myriam
                                                          Peyrounette<br>
                                                          <br>
                                                          <br>
                                                          -- <br>
                                                          Myriam
                                                          Peyrounette<br>
                                                          CNRS/IDRIS -
                                                          HLST<br>
                                                          --<br>
                                                          <br>
                                                          </blockquote>
                                                          </div>
                                                          <br
                                                          clear="all">
                                                          <div><br>
                                                          </div>
                                                          -- <br>
                                                          <div dir="ltr"
class="gmail-m_7299408251829905453gmail-m_7961152398334556293gmail-m_4941328961016005032gmail-m_4553173887686987135gmail-m_-3242500023102749998gmail_signature">
                                                          <div dir="ltr">
                                                          <div>
                                                          <div dir="ltr">
                                                          <div>
                                                          <div dir="ltr">
                                                          <div>What most
                                                          experimenters
                                                          take for
                                                          granted before
                                                          they begin
                                                          their
                                                          experiments is
                                                          infinitely
                                                          more
                                                          interesting
                                                          than any
                                                          results to
                                                          which their
                                                          experiments
                                                          lead.<br>
                                                          -- Norbert
                                                          Wiener</div>
                                                          <div><br>
                                                          </div>
                                                          <div><a
                                                          href="http://www.cse.buffalo.edu/%7Eknepley/"
target="_blank" moz-do-not-send="true">https://www.cse.buffalo.edu/~knepley/</a><br>
                                                          </div>
                                                          </div>
                                                          </div>
                                                          </div>
                                                          </div>
                                                          </div>
                                                          </div>
                                                          </div>
                                                          </div>
                                                          </blockquote>
                                                          <br>
                                                          <pre class="gmail-m_7299408251829905453gmail-m_7961152398334556293gmail-m_4941328961016005032gmail-m_4553173887686987135gmail-m_-3242500023102749998moz-signature" cols="72">-- 
Myriam Peyrounette
CNRS/IDRIS - HLST
--
</pre>
                                                          </div>
                                                          </blockquote>
                                                        </div>
                                                        <br clear="all">
                                                        <div><br>
                                                        </div>
                                                        -- <br>
                                                        <div dir="ltr"
class="gmail-m_7299408251829905453gmail-m_7961152398334556293gmail-m_4941328961016005032gmail-m_4553173887686987135gmail_signature">
                                                          <div dir="ltr">
                                                          <div>
                                                          <div dir="ltr">
                                                          <div>
                                                          <div dir="ltr">
                                                          <div>What most
                                                          experimenters
                                                          take for
                                                          granted before
                                                          they begin
                                                          their
                                                          experiments is
                                                          infinitely
                                                          more
                                                          interesting
                                                          than any
                                                          results to
                                                          which their
                                                          experiments
                                                          lead.<br>
                                                          -- Norbert
                                                          Wiener</div>
                                                          <div><br>
                                                          </div>
                                                          <div><a
                                                          href="http://www.cse.buffalo.edu/%7Eknepley/"
target="_blank" moz-do-not-send="true">https://www.cse.buffalo.edu/~knepley/</a><br>
                                                          </div>
                                                          </div>
                                                          </div>
                                                          </div>
                                                          </div>
                                                          </div>
                                                        </div>
                                                      </div>
                                                    </blockquote>
                                                    <br>
                                                    <pre class="gmail-m_7299408251829905453gmail-m_7961152398334556293gmail-m_4941328961016005032gmail-m_4553173887686987135moz-signature" cols="72">-- 
Myriam Peyrounette
CNRS/IDRIS - HLST
--
</pre>
                                                  </div>
                                                </blockquote>
                                              </div>
                                            </blockquote>
                                            <br>
                                            <pre class="gmail-m_7299408251829905453gmail-m_7961152398334556293gmail-m_4941328961016005032moz-signature" cols="72">-- 
Myriam Peyrounette
CNRS/IDRIS - HLST
--
</pre>
                                          </div>
                                        </blockquote>
                                      </div>
                                    </blockquote>
                                    <br>
                                    <pre class="gmail-m_7299408251829905453gmail-m_7961152398334556293moz-signature" cols="72">-- 
Myriam Peyrounette
CNRS/IDRIS - HLST
--
</pre>
                                  </blockquote>
                                  <br>
                                  <pre class="gmail-m_7299408251829905453gmail-m_7961152398334556293moz-signature" cols="72">-- 
Myriam Peyrounette
CNRS/IDRIS - HLST
--
</pre>
                                </div>
                              </blockquote>
                            </div>
                          </div>
                        </div>
                      </div>
                    </div>
                  </div>
                </div>
              </blockquote>
              <br>
              <pre class="gmail-m_7299408251829905453moz-signature" cols="72">-- 
Myriam Peyrounette
CNRS/IDRIS - HLST
--
</pre>
            </div>
          </blockquote>
        </div>
        <br clear="all">
        <div><br>
        </div>
        -- <br>
        <div dir="ltr" class="gmail_signature">
          <div dir="ltr">
            <div>
              <div dir="ltr">
                <div>
                  <div dir="ltr">
                    <div>What most experimenters take for granted before
                      they begin their experiments is infinitely more
                      interesting than any results to which their
                      experiments lead.<br>
                      -- Norbert Wiener</div>
                    <div><br>
                    </div>
                    <div><a
                        href="http://www.cse.buffalo.edu/%7Eknepley/"
                        target="_blank" moz-do-not-send="true">https://www.cse.buffalo.edu/~knepley/</a><br>
                    </div>
                  </div>
                </div>
              </div>
            </div>
          </div>
        </div>
      </div>
    </blockquote>
    <br>
    <pre class="moz-signature" cols="72">-- 
Myriam Peyrounette
CNRS/IDRIS - HLST
--
</pre>
  </body>
</html>