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Hi,<br>
<br>
I have been using the GUI environment to do debugging so I am a bit
reluctant to learn Valgrind as its outputs seems a bit daunting.
But I guess John is right. I've been spending these few days
learning bit by bit.<br>
<br>
I realised that the error occurs in computerhs, at:<br>
<br>
<b>call DMDAVecRestoreArrayF90(da,b,array,ierr)</b><br>
<br>
==27464== Invalid write of size 8<br>
==27464== at 0x402835: computerhs_ (ex29f.F90:119)<br>
==27464== Address 0xfffffffffffffef0 is not stack'd, malloc'd or
(recently) free'd<br>
==27464== <br>
[0]PETSC ERROR:
------------------------------------------------------------------------<br>
[0]PETSC ERROR: Caught signal number 11 SEGV: Segmentation
Violation, probably memory access out of range<br>
[0]PETSC ERROR: Try option -start_in_debugger or
-on_error_attach_debugger<br>
[0]PETSC ERROR: or see
<a class="moz-txt-link-freetext" href="http://www.mcs.anl.gov/petsc/documentation/faq.html#valgrind">http://www.mcs.anl.gov/petsc/documentation/faq.html#valgrind</a>[0]PETSC
ERROR: or try <a class="moz-txt-link-freetext" href="http://valgrind.org">http://valgrind.org</a> on GNU/linux and Apple Mac OS X to
find memory corruption errors<br>
[0]PETSC ERROR: likely location of problem given in stack below<br>
[0]PETSC ERROR: --------------------- Stack Frames
------------------------------------<br>
[0]PETSC ERROR: Note: The EXACT line numbers in the stack are not
available,<br>
[0]PETSC ERROR: INSTEAD the line number of the start of the
function<br>
[0]PETSC ERROR: is given.<br>
[0]PETSC ERROR: [0] DM user function line 0 unknownunknown<br>
[0]PETSC ERROR: [0] DMComputeFunction line 2085
/home/wtay/Codes/petsc-dev/src/dm/interface/dm.c<br>
[0]PETSC ERROR: [0] KSPSetUp line 182
/home/wtay/Codes/petsc-dev/src/ksp/ksp/interface/itfunc.c<br>
[0]PETSC ERROR: --------------------- Error Message
------------------------------------<br>
[0]PETSC ERROR: Signal received!<br>
<br>
I have checked that "array" 's values are correct. This statement
executed without problems in VS2008. If I replace the above with
something like:<br>
<br>
<b>call VecSet(b,Hy,ierr)</b><br>
<br>
Everything is fine in Linux.<br>
<br>
Is there something wrong with <b>DMDAVecRestoreArrayF90</b>?<br>
<br>
My code in the area is:<br>
<br>
call
DMDAGetCorners(da,xs,ys,PETSC_NULL_INTEGER,xm,ym,PETSC_NULL_INTEGER,ierr)<br>
<br>
call DMDAVecGetArrayF90(da,b,array,ierr)<br>
<br>
do j = ys,ys+ym-1<br>
<br>
do i = xs,xs+xm-1<br>
<br>
array(i,j) =
exp(-(i*Hx)*(i*Hx)/nu)*exp(-(j*Hy)*(j*Hy)/nu)*Hx*Hy<br>
<br>
end do<br>
<br>
end do<br>
<br>
call DMDAVecRestoreArrayF90(da,b,array,ierr)<br>
<br>
call VecAssemblyBegin(b,ierr)<br>
<br>
call VecAssemblyEnd(b,ierr)<br>
<br>
<br>
<pre class="moz-signature" cols="72">Yours sincerely,
TAY wee-beng</pre>
<br>
On 8/5/2012 9:41 PM, John Mousel wrote:
<blockquote
cite="mid:CA+zegpnTN40NUz+hD=BCqgv2kyz8sywzGDz+jDeVH3kXb+LSBw@mail.gmail.com"
type="cite">TAY wee-bing,<br>
<br>
If you want to be a programmer that writes interesting and
reliable code, you need to be willing to use the tools of the
trade. I can't think of a bigger time-saver than Valgrind. I would
suggest that you learn to use it and use it a lot. I bet it will
lead you to the root of your problem pretty quickly.<br>
<br>
John<br>
<br>
<div class="gmail_quote">On Tue, May 8, 2012 at 2:17 PM, TAY
wee-beng <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:zonexo@gmail.com" target="_blank">zonexo@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000"> Hi,<br>
<br>
I compiled and run my code under visual studio 2008 with
intel fortran. Everything works ok.<br>
<br>
However, when I tried to run the code in linux, I got the
error as below. The error happens when KSPSetUp(ksp,ierr) is
called.<br>
<br>
However, I am not able to print VecView or MatView to view
if there's any errors. Is there any recommendation for
debugging? I hope I do not need to valgrind if possible.<br>
<br>
[0]PETSC ERROR:
------------------------------------------------------------------------<br>
[0]PETSC ERROR: Caught signal number 11 SEGV: Segmentation
Violation, probably memory access out of range<br>
[0]PETSC ERROR: Try option -start_in_debugger or
-on_error_attach_debugger<br>
[0]PETSC ERROR: or see <a moz-do-not-send="true"
href="http://www.mcs.anl.gov/petsc/documentation/faq.html#valgrind"
target="_blank">http://www.mcs.anl.gov/petsc/documentation/faq.html#valgrind</a>[0]PETSC
ERROR: or try <a moz-do-not-send="true"
href="http://valgrind.org" target="_blank">http://valgrind.org</a>
on GNU/linux and Apple Mac OS X to find memory corruption
errors<br>
[0]PETSC ERROR: likely location of problem given in stack
below<br>
[0]PETSC ERROR: --------------------- Stack Frames
------------------------------------<br>
[0]PETSC ERROR: Note: The EXACT line numbers in the stack
are not available,<br>
[0]PETSC ERROR: INSTEAD the line number of the start
of the function<br>
[0]PETSC ERROR: is given.<br>
[0]PETSC ERROR: [0] DM user function line 0 unknownunknown<br>
[0]PETSC ERROR: [0] DMComputeFunction line 2085
/home/wtay/Codes/petsc-dev/src/dm/interface/dm.c<br>
[0]PETSC ERROR: [0] KSPSetUp line 182
/home/wtay/Codes/petsc-dev/src/ksp/ksp/interface/itfunc.c<br>
[0]PETSC ERROR: --------------------- Error Message
------------------------------------<br>
[0]PETSC ERROR: Signal received!<br>
[0]PETSC ERROR:
------------------------------------------------------------------------<br>
[0]PETSC ERROR: Petsc Development HG revision:
7ecdd63ec420b1659b960e65d96e822c5ac1a968 HG Date: Mon May
07 21:42:26 2012 -0500<br>
[0]PETSC ERROR: See docs/changes/index.html for recent
updates.<br>
[0]PETSC ERROR: See docs/faq.html for hints about trouble
shooting.<br>
[0]PETSC ERROR: See docs/index.html for manual pages.<br>
[0]PETSC ERROR:
------------------------------------------------------------------------<br>
[0]PETSC ERROR: ./ex29f on a petsc-3.2 named hpc12 by wtay
Tue May 8 20:45:42 2012<br>
[0]PETSC ERROR: Libraries linked from
/home/wtay/Lib/petsc-3.2-dev_shared_debug/lib<br>
[0]PETSC ERROR: Configure run at Tue May 8 10:47:59 2012<br>
[0]PETSC ERROR: Configure options
--with-mpi-dir=/opt/openmpi-1.5.3/
--with-blas-lapack-dir=/opt/intelcpro-11.1.059/mkl/lib/em64t/
--with-debugging=1 --download-hypre=1
--prefix=/home/wtay/Lib/petsc-3.2-dev_shared_debug
--known-mpi-shared=1 --with-shared-libraries<br>
[0]PETSC ERROR:
------------------------------------------------------------------------<br>
[0]PETSC ERROR: User provided function() line 0 in unknown
directory unknown file<br>
--------------------------------------------------------------------------<br>
MPI_ABORT was invoked on rank 0 in communicator
MPI_COMM_WORLD <br>
with errorcode 59.<br>
<br>
NOTE: invoking MPI_ABORT causes Open MPI to kill all MPI
processes.<br>
You may or may not see output from other processes,
depending on<br>
exactly when Open MPI kills them.<br>
<br>
<pre cols="72">Yours sincerely,
TAY wee-beng</pre>
<br>
On 5/5/2012 1:43 AM, Matthew Knepley wrote:
<blockquote type="cite">
<div class="gmail_extra">On Fri, May 4, 2012 at 5:42 PM,
TAY wee-beng <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:zonexo@gmail.com" target="_blank">zonexo@gmail.com</a>></span>
wrote:<br>
<div class="gmail_quote">
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000"> Hi,<br>
<br>
I wonder if you people are interested to include
my ex29 fortran version in the petsc examples,
which can help people who are using fortran.<br>
</div>
</blockquote>
<div><br>
</div>
<div>Yes, we will definitely include it. Please send
the source, and a representative output with run
options.</div>
<div><br>
</div>
<div> Thanks,</div>
<div><br>
</div>
<div> Matt</div>
<div> </div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000"> Thanks.<br>
<pre cols="72">Yours sincerely,
TAY wee-beng</pre>
<br>
On 4/5/2012 9:28 PM, Matthew Knepley wrote:
<blockquote type="cite">
<div class="gmail_extra">On Fri, May 4, 2012 at
3:24 PM, TAY wee-beng <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:zonexo@gmail.com"
target="_blank">zonexo@gmail.com</a>></span>
wrote:<br>
<div class="gmail_quote">
<blockquote class="gmail_quote"
style="margin:0 0 0 .8ex;border-left:1px
#ccc solid;padding-left:1ex"> <br>
On 4/5/2012 9:16 PM, Barry Smith wrote:<br>
<blockquote class="gmail_quote"
style="margin:0 0 0 .8ex;border-left:1px
#ccc solid;padding-left:1ex"> Do an
hg pull and then run make in
src/mat/interface/ftn-custom/<br>
<br>
Then it should link.<br>
<br>
Barry<br>
<br>
There was a E missing from the all
caps name of the function.<br>
</blockquote>
After hg pull, I did:<br>
<br>
cd src//mat/interface/ftn-custom/<br>
<br>
User@User-PC
/cygdrive/c/temp/petsc-dev/src/mat/interface/ftn-custom<br>
$ make<br>
make[1]: Warning: File
`/cygdrive/c/temp/petsc-dev/petsc-3.2-dev_win32_vs2008/lib/libpetsc.lib(zmatregf.o)'
has modification time 787 s in the future<br>
make[1]: Nothing to be done for `libc'.<br>
make[1]: warning: Clock skew detected.
Your build may be incomplete.<br>
<br>
But it still can't work.<br>
</blockquote>
<div><br>
</div>
<div>Something is messed up with the clock
on this machine.</div>
<div><br>
</div>
<div>HOWEVER, development requires certain
basic skills in order to debug your work.
We</div>
<div>cannot be the ones debugging your code.
Now</div>
<div><br>
</div>
<div> nm $PETSC_ARCH/lib/libpetsc.a | grep
-i MatNullSpaceRemove</div>
<div><br>
</div>
<div> will look for the symbol.</div>
<div><br>
</div>
<div> Matt</div>
<div> </div>
<blockquote class="gmail_quote"
style="margin:0 0 0 .8ex;border-left:1px
#ccc solid;padding-left:1ex">
<blockquote class="gmail_quote"
style="margin:0 0 0 .8ex;border-left:1px
#ccc solid;padding-left:1ex"> <br>
<br>
On May 4, 2012, at 2:11 PM, Matthew
Knepley wrote:<br>
<br>
<blockquote class="gmail_quote"
style="margin:0 0 0
.8ex;border-left:1px #ccc
solid;padding-left:1ex"> On Fri, May
4, 2012 at 3:01 PM, TAY wee-beng<<a
moz-do-not-send="true"
href="mailto:zonexo@gmail.com"
target="_blank">zonexo@gmail.com</a>>
wrote:<br>
<br>
On 4/5/2012 5:17 PM, Matthew Knepley
wrote:<br>
<blockquote class="gmail_quote"
style="margin:0 0 0
.8ex;border-left:1px #ccc
solid;padding-left:1ex"> On Fri, May
4, 2012 at 11:05 AM, TAY
wee-beng<<a
moz-do-not-send="true"
href="mailto:zonexo@gmail.com"
target="_blank">zonexo@gmail.com</a>>
wrote:<br>
<br>
On 4/5/2012 3:05 PM, Matthew Knepley
wrote:<br>
<blockquote class="gmail_quote"
style="margin:0 0 0
.8ex;border-left:1px #ccc
solid;padding-left:1ex"> On Fri,
May 4, 2012 at 8:59 AM, TAY
wee-beng<<a
moz-do-not-send="true"
href="mailto:zonexo@gmail.com"
target="_blank">zonexo@gmail.com</a>>
wrote:<br>
<br>
Hi,<br>
<br>
Is there anything else I can try
to get it working right?<br>
<br>
The MatGetNullSpaceRemove() is
missing.<br>
</blockquote>
Where should I add
MatGetNullSpaceRemove and what are
its syntax? I googled but there's no
results.<br>
<br>
Fixed in p;etsc-dev:<br>
<br>
<a moz-do-not-send="true"
href="http://www.mcs.anl.gov/petsc/petsc-dev/docs/manualpages/Mat/MatNullSpaceRemove.html"
target="_blank">http://www.mcs.anl.gov/petsc/petsc-dev/docs/manualpages/Mat/MatNullSpaceRemove.html</a><br>
</blockquote>
I just compiled the updated petsc-dev
but I got the same error msg when I
use:<br>
<br>
call
MatNullSpaceRemove(nullspace,b,PETSC_NULL,ierr)<br>
<br>
error LNK2019: unresolved external
symbol MATNULLSPACEREMOVE referenced
in function COMPUTERHS<br>
1>c:\obj_tmp\ex29f\Debug\ex29f.exe
: fatal error LNK1120: 1 unresolved
externals<br>
<br>
That function is in:<br>
<br>
src/mat/interface/ftn-custom/zmatrixf.c<br>
<br>
Did that compile? Can you see the
symbol in libpetsc.a?<br>
<br>
Matt<br>
<br>
<blockquote class="gmail_quote"
style="margin:0 0 0
.8ex;border-left:1px #ccc
solid;padding-left:1ex"> Matt<br>
<br>
Thanks.<br>
<blockquote class="gmail_quote"
style="margin:0 0 0
.8ex;border-left:1px #ccc
solid;padding-left:1ex"> Matt<br>
<br>
Thanks！<br>
<br>
<br>
On 2/5/2012 10:11 PM, Matthew
Knepley wrote:<br>
<blockquote class="gmail_quote"
style="margin:0 0 0
.8ex;border-left:1px #ccc
solid;padding-left:1ex"> On Wed,
May 2, 2012 at 1:55 PM, TAY
wee-beng<<a
moz-do-not-send="true"
href="mailto:zonexo@gmail.com"
target="_blank">zonexo@gmail.com</a>>
wrote:<br>
Hi,<br>
<br>
I did a MatView and VecView on
both C and Fortran, right after
Mat and Vec assembly. I have
attached the printout below.
They are exactly the same, but
yet the result is different in
Neumann condition. However, the
dirichlet condition gives the
correct ans. Is there anything
else that could be wrong even if
the Mat and Vec are the same?<br>
<br>
Did you set the null space for
the matrix when you have Neumann
conditions?<br>
</blockquote>
Yes, for the matrix, I set as:<br>
<br>
call
MatNullSpaceCreate(PETSC_COMM_WORLD,PETSC_TRUE,0,PETSC_NULL_OBJECT,nullspace,ierr)<br>
<br>
call
MatSetNullSpace(jac,nullspace,ierr)<br>
<br>
call
MatNullSpaceDestroy(nullspace,ierr)<br>
<br>
for the Vec,<br>
<br>
call
MatNullSpaceCreate(PETSC_COMM_WORLD,PETSC_TRUE,0,PETSC_NULL_OBJECT,nullspace,ierr)<br>
<br>
!call
MatNullSpaceRemove(nullspace,b,PETSC_NULL,ierr)<br>
<br>
call
MatNullSpaceDestroy(nullspace,ierr)<br>
<br>
MatNullSpaceRemove was comment out
because there's error during
linking<br>
<br>
<br>
<blockquote class="gmail_quote"
style="margin:0 0 0
.8ex;border-left:1px #ccc
solid;padding-left:1ex"> Matt<br>
<br>
Thanks!<br>
<br>
Fortran:<br>
<br>
Matrix Object: 1 MPI processes<br>
type: seqaij<br>
row 0: (0, 2) (1, -1) (3, -1)<br>
row 1: (0, -1) (1, 3) (2, -1)
(4, -1)<br>
row 2: (1, -1) (2, 2) (5, -1)<br>
row 3: (0, -1) (3, 3) (4, -1)
(6, -1)<br>
row 4: (1, -1) (3, -1) (4, 4)
(5, -1) (7, -1)<br>
row 5: (2, -1) (4, -1) (5, 3)
(8, -1)<br>
row 6: (3, -1) (6, 2) (7, -1)<br>
row 7: (4, -1) (6, -1) (7, 3)
(8, -1)<br>
row 8: (5, -1) (7, -1) (8, 2)<br>
Vector
Object:Vec_0000000084000000_0 1
MPI processes<br>
type: mpi<br>
Process [0]<br>
0.25<br>
0.0205213<br>
1.135e-005<br>
0.0205213<br>
0.00168449<br>
9.31663e-007<br>
1.135e-005<br>
9.31663e-007<br>
5.15289e-010<br>
Vector
Object:Vec_0000000084000000_1 1
MPI processes<br>
type: mpi<br>
Process [0]<br>
0.14924<br>
0.0242397<br>
-0.0260347<br>
0.0242397<br>
-0.0256192<br>
-0.0400102<br>
-0.0260347<br>
-0.0400102<br>
-0.0400102<br>
Press any key to continue . . .<br>
<br>
C:<br>
<br>
Matrix Object: 1 MPI processes<br>
type: seqaij<br>
row 0: (0, 2) (1, -1) (3, -1)<br>
row 1: (0, -1) (1, 3) (2, -1)
(4, -1)<br>
row 2: (1, -1) (2, 2) (5, -1)<br>
row 3: (0, -1) (3, 3) (4, -1)
(6, -1)<br>
row 4: (1, -1) (3, -1) (4, 4)
(5, -1) (7, -1)<br>
row 5: (2, -1) (4, -1) (5, 3)
(8, -1)<br>
row 6: (3, -1) (6, 2) (7, -1)<br>
row 7: (4, -1) (6, -1) (7, 3)
(8, -1)<br>
row 8: (5, -1) (7, -1) (8, 2)<br>
Vector Object:Vec_0x1d3b000_0 1
MPI processes<br>
type: mpi<br>
Process [0]<br>
0.25<br>
0.0205212<br>
1.135e-05<br>
0.0205212<br>
0.00168449<br>
9.31663e-07<br>
1.135e-05<br>
9.31663e-07<br>
5.15288e-10<br>
Vector Object:Vec_0x1d3b000_1 1
MPI processes<br>
type: mpi<br>
Process [0]<br>
0.139311<br>
0.0305751<br>
-0.0220633<br>
0.0305751<br>
-0.0135158<br>
-0.042185<br>
-0.0220633<br>
-0.042185<br>
-0.058449<br>
<br>
<br>
<br>
Yours sincerely,<br>
<br>
TAY wee-beng<br>
<br>
<br>
On 1/5/2012 11:54 PM, Matthew
Knepley wrote:<br>
<blockquote class="gmail_quote"
style="margin:0 0 0
.8ex;border-left:1px #ccc
solid;padding-left:1ex"> On
Tue, May 1, 2012 at 5:48 PM,
TAY wee-beng<<a
moz-do-not-send="true"
href="mailto:zonexo@gmail.com"
target="_blank">zonexo@gmail.com</a>>
wrote:<br>
Hi,<br>
<br>
Do you mean my method is
wrong?<br>
<br>
I am following the template of
ex22f,<br>
<br>
where the variables are
declared as :<br>
<br>
PetscScalar v(5)<br>
<br>
MatStencil row(4),col(4,5)<br>
<br>
Hence,<br>
<br>
for the neumann BC<br>
<br>
num = 1<br>
<br>
if (j/=0) then<br>
<br>
v(num) =
-rho*HxdHy<br>
<br>
col(MatStencil_i,num) = i<br>
<br>
col(MatStencil_j,num) = j-1<br>
<br>
num = num +
1<br>
<br>
end if<br>
<br>
if (i/=0) then<br>
<br>
v(num) =
-rho*HydHx<br>
<br>
col(MatStencil_i,num) = i-1<br>
<br>
col(MatStencil_j,num) = j<br>
<br>
num = num +
1<br>
<br>
end if<br>
<br>
if (i/=mx-1)
then<br>
<br>
v(num) =
-rho*HydHx<br>
<br>
col(MatStencil_i,num) = i+1<br>
<br>
col(MatStencil_j,num) = j<br>
<br>
num = num +
1<br>
<br>
end if<br>
<br>
if (j/=my-1)
then<br>
<br>
v(num) =
-rho*HxdHy<br>
<br>
col(MatStencil_i,num) = i<br>
<br>
col(MatStencil_j,num) = j+1<br>
<br>
num = num +
1<br>
<br>
end if<br>
<br>
v(num) =
((num-1)/2.0)*rho*(HxdHy +
HydHx)<br>
<br>
print *, v<br>
<br>
col(MatStencil_i,num) = i<br>
<br>
col(MatStencil_j,num) = j<br>
<br>
!num = num + 1<br>
<br>
call
MatSetValuesStencil(jac,i1,row,num,col,v,INSERT_VALUES,ierr)<br>
<br>
I do not get any more out of
range error. However,my ans is
still different from that of
ex29 in C.<br>
<br>
This is very simple. You have
an error in your code.
Checking it is very simple:
run the code and<br>
break in MatSetValues(). Make
sure ex29 makes calls with
exactly the same indices as
your ex29f.<br>
<br>
Matt<br>
<br>
Yours sincerely,<br>
<br>
TAY wee-beng<br>
<br>
-- <br>
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<br>
</blockquote>
<br>
<br>
-- <br>
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<br>
</blockquote>
<br>
<br>
-- <br>
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<br>
</blockquote>
<br>
<span><font color="#888888"> <br>
-- <br>
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<br>
</font></span></blockquote>
<span><font color="#888888"> <br>
<span><font color="#888888"> <br>
-- <br>
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<br>
</font></span></font></span></blockquote>
<span><font color="#888888"> </font></span></blockquote>
<span><font color="#888888"> </font></span></blockquote>
<span><font color="#888888"> </font></span></div>
<span><font color="#888888"> <br>
<br clear="all">
<span class="HOEnZb"><font color="#888888">
<div><br>
</div>
-- <br>
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<br>
</font></span></font></span></div>
<span class="HOEnZb"><font color="#888888"> </font></span></blockquote>
<span class="HOEnZb"><font color="#888888"> </font></span></div>
<span class="HOEnZb"><font color="#888888"> </font></span></blockquote>
<span class="HOEnZb"><font color="#888888"> </font></span></div>
<span class="HOEnZb"><font color="#888888"> <br>
<br clear="all">
<div><br>
</div>
-- <br>
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<br>
</font></span></div>
</blockquote>
</div>
</blockquote>
</div>
<br>
</blockquote>
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