krj@na.toronto.edu (Ken Jackson) (06/22/89)
NAgMAg Wednesday, June 21 1989 Volume 89 Issue 14
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%% The official electronic digest of the NAG Users Association %%
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Today's Topics
Accuracy of the F02BJF
Sparse Matrix Package
Response to Volterra Integral Equation Request
Usage Statistics
NAGUA meeting update
%% Still hot in Kent I've replaced the rice on the allotment
%% (sown after the monsoon earlier this month) with cacti.
%%
%% A few more articles this week -- please keep them rolling in.
%% I believe it really helps to put a digest out approximately
%% weekly as contributers then get a reasonably fast turn round
%% on queries.
%%
%% Tim
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Date: Wed, 14 Jun 89 13:21:49 BST
From: MBBGPTB@cms.manchester-computing-centre.ac.uk
Subject: Accuracy of the F02BJF
I recently used the generalized eigenvalue routine F02BJF. For
the accuracy control I called the function X02AAF(0.0e0) and
I expect using this I will get a reasonably accurate result.
What I found was a very inacurate result. My matrix is quite
small (19 x 19) and has a pair of complex e'values; the rest
of the eigenvalues are real. Using F02BJF it turned out that
all the eigenvalues are complex with quite significant imaginary
part. (I ran my program on IBM-CMS with double length).
Have I done something wrong ?
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Date: Thu, 15 Jun 89 12:06:38 EET
From: J}rgen Bruchhaus <MI004@dk0umi1.earn>
Subject: Sparse Matrix Package
I need FORTRAN-subroutines for the usual operations on sparse matrices
( including factorization ) .
Does anyone know about a freely available package ?
Thanks in advance ,
Juergen Bruchhaus
Institute of Mathematics
University of Cologne
Weyertal 86-90
D-5000 Koeln 41
( BITNET : MI004@DK0UMI1 )
Acknowledge-To: <MI004@DK0UMI1>
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Date: Thu, 15 JUN 89 16:19:53 GMT
From: CAROLINE@vax.nag.co.uk
Subject: Response to Volterra Integral Equation Request
The following item is in response to the request from Harvey
Richardson, Heriot-Watt University in issue 12.
Routines for Volterra Integral Equations
----------------------------------------
Algorithms for the numerical solution of Volterra integral equations of
the first and second kind are under consideration in the D05 chapter of
the Fortran library.
In fact, a routine for the solution of nonlinear convolution integral
equation of the second kind, which occurs in real life problems,
t
(1) y(t) = f(t) + I k(t-s)g(s,y(s)) ds
a
has been developed and will appear in Mark 14 of the Fortran library.
This routine (D05BAF) uses a variety of reducible linear multistep
methods of Adams and backward differentiation formulae type; the user
should supply a tolerance for the desired accuracy.
Equation (1) is a subclass of the general second kind Volterra equation
t
(2) y(t) = f(t) + I K(t,s,y(s)) ds
a
with K(t,s,y(s)) = k(t-s)g(s,y(s)).
To develop efficient and reliable codes for Volterra equations, the
structure of the kernel K(t,s,y(s)) should be considered and the choice
of the method is very important. For example, in solving (1) the
number of function evaluations are reduced significantly due to the
convolution nature of the kernel.
For kernels with weak singularities of the form
-1/2
k(t,s,y) = (t-s) H(t,s,y)
special methods exist and a separate routine will be developed; again
the structure H(t,s,y) is important.
Routines for the solution of the general equation (2) are being
considered. In the meantime we are preparing codes to exploit commonly
occuring problems with special kernel structures.
Mishi Derakhshan
15 June 1989
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Date: Fri, 16 Jun 89 16:33:40 EDT
From: Steve Hotovy <SGH@cornellf.earn>
Subject: Usage Statistics
I read about tracking subroutine calls in Issue 12 of NagMag. We are
very interested in doing something like this here at Cornell. Could you
point me in the right direction for more information?
Steve Hotovy
CNSF
%% Correct me David if I'm wrong, but I thought all implementations
%% of routine call accounting had been site dependent `hacks'. These
%% are therefore very machine/system dependent. I'd like to see NAG
%% put the hooks in the sources to allow such accounting to be
%% implemented. Would others be interested in this? Tim
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Date: Tue, 20 JUN 89 15:30:24 GMT
From: CAROLINE@vax.nag.co.uk
Subject: NAGUA meeting update
NAGUA'89
--------
Conference latest - Julian Gallop from Rutherford Appleton Laboratory
will be giving the presentation on 'Library
Management in a Network'
- Ron Furzeland from Koninklijkeshell-Laboratorium,
Amsterdam, one of the speakers on Industrial
Applications of NAG Software, will be speaking on
'Differential Equation Software in the
Petrochemical Industry: Requirements and Needs'.
Just in case any of you are not yet NAGUA members (although I'm sure
you all are, as NAGMAG is a NAGUA service), membership of just #30, or
$60 in North America, entitles you to a discount of #30 at the one day
tutorial AND a discount of #30 at the main meeting. So if you will be
coming to the whole conference or even just the main meeting, then it
certainly makes sense to join. There, that's my sales pitch for now.
Caroline Foers
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%% END OF ISSUE
---------------------------
Reposted by
--
Kenneth R. Jackson, krj@na.toronto.edu (on Internet, CSNet,
Computer Science Dept., ARPAnet, BITNET)
University of Toronto, krj@na.utoronto.ca (CDNnet and other
Toronto, Canada M5S 1A4 X.400 nets (Europe))
(Phone: 416-978-7075) ...!{uunet,pyramid,watmath,ubc-cs}!utai!krj