"TAngent Search Concept" (TASC) - 2-dimensional example

February 11, 2010
Toy surface is the modified by factor 0.03 NFK, see Hirsch/Quapp: Chem Phys Lett 395 (2004) 150-156, and Quapp/Bofill: J Computat Chem 2010 (submitted)

The Fortran program is Tasc2DmodNFK2010.f. Translate it by g77, and execute it: that is all.

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Download the program Tasc2DmodNFK2010.f
The next is a Mma file to see the result file chain.dat.

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Download the Mma file NFK0p03byTASC.in
For comparison, my chain.dat is here: Download

"TAngent Search Concept" (TASC) - modular Version

Version 1.1, Nov 1, 2001
TASC does a pathfollowing along the gradient extremal to the smallest eigenvalue, being usually the valley floor line.
References
W.Quapp, M.Hirsch, D. Heidrich: Theor Chem Acc (2000) 105: 145-155,
W.Quapp: Computers and Mathem with Applic (2001) 41,No.3/4: 407-414

The convergence proof for TASC is outlined in:
W.Quapp: Optimization, 52,No.3 (2003), 317-331, "A Valley Following Method"


For the application of the TASC, we have written a Fortran program. This program can be called by a script which also calls the quantum chemical program / any program for the function.
TASC is based on the RGF program. The principal change is that RSEL now is not constant, but it is replaced by the tangent TANG after a projector step
(in Line 424: call ortcompl(tang,proj,unit,nn) ).
Further changes are coming from an additional step length search. This causes a "double" step for every predictor: first the direction is calculated, and in the second, real step the corresponding step length is used.
The RGF-program needs as input the first point,
the gradient at every point, and the hessian at least at first point,
the Wilson B-matrix at every point (if the program should use the metric of internal coordinates).
TASC - step length search also needs the energy, the function value.
(This causes a change in the param.rgf file, and also changes in the utils.f - below there is version 2.2 of the RGF program being compatible with this TASC version1.)

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Download the program TASC.f
Download the program utilities utils.f
Download the TASC-Makefile in Linux
Download an example SCRIPT for a TASC application with Gamess-UK

the Manual (Aug 2001) for modular TASC
TASC example path for molecule H2CO uphill from Min to SP
Download the RGF program (adapted to this TASC version)
RGF example path for molecule H2CO uphill from Min to SP

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TASC Version 1.1, Nov 1, 2001, W.Quapp, E-Mail: quapp@uni-leipzig.de
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