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110 lines
4.3 KiB
TeX
110 lines
4.3 KiB
TeX
%
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% $Id$
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%
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\label{sec:fourindex}
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{\bf THIS SECTION IS BEING REWRITTEN}
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%{\bf ????????????????????}
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%\Large
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%**What does this module really do? Is it invoked by any module other than
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%DIRECT\_MP2?
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%\normalsize
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%
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%% The four-index transformation module is not designed for explicit
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%% invocation but rather as a utility module for other tasks (e.g. direct
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%% MP2 section \ref{sec:mp2}). However, there are input parameters which
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%% may be set to modify the default behavior of the four-index
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%% transformation module which may enhance performance.
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%
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%The four-index transformation module is a utility invoked by the fully
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%direct MP2 module (see Section \ref{sec:mp2}). For most applications,
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%the default parameters for the four-index transformation will be adequate,
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%but in some instances, the user may wish to enhance the performance of
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%the module. This can be done by specifying \verb+SET+ directives for
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%selected parameters. The following sections describe the options
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%currently available for this module.
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%
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%\section{Algorithm for the Four-Index Transformation}
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%
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%The code currently contains two algorithms for the four-index transformation.
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%The algorithm to use for a given calculation can be selected by specifying
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%a \verb+SET+ directive of the form,
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%
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%\begin{verbatim}
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% set "fourindex:method" <string method default twofold>
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%\end{verbatim}
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%
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%% There is a choice of two algorithms for effecting the transformation.
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%The default entry for the string \verb+method+ is \verb+twofold+, which
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%specifies ***what?***. This option should be used in almost all instances.
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%However, in cases of high orders of parallelism (i.e., more than 200 nodes),
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% better throughput may be obtained with the alternative algorithm,
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%obtained by setting \verb+method+ to \verb+sixfold+.
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%
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%\section{AO Integral Blocking and Block Length for the Four-Index Transformation}
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%
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%The default in the four-index transformation is to have no blocking in
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%the AO integral generation. Blocking can be specified explicitly using a
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%\verb+SET+ directive of the form,
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%
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%\begin{verbatim}
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% set "fourindex:aoblock" <logical aoblock default .false.>
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%\end{verbatim}
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%
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%Entering a value of \verb+.true.+ for the logical variable \verb+aoblock+
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%enables blocking in the AO integral generation. This may result in
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%substantial performance enhancement in cases with many identical
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%atoms and basis sets.
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%
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%The default is 10 for the vector length in the critical first index
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%transformation of the four-index transformation algorithm. The user has
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%the option of specifying the vector length explicitly by entering a
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%\verb+SET+ directive of the form,
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%
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%\begin{verbatim}
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% set "fourindex:blocklength" <integer blocklength default 10>
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%\end{verbatim}
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%
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%% This parameter determines the vector length in the critical first
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%% index transformation.
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%
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%For larger basis sets, it may be profitable to increase the vector
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%length by specifying a value larger than 10 for the integer variable
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%\verb+blocklength+. However, this value should {\em
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% not} exceed $N_{bf} / 3$, since the cost of the redundant computation
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%in the square matrix multiplication would in that case exceed the
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%gain from a longer vector length.
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%
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%\Large
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%***What is $N_{bf} / 3$?
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%\normalsize
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%
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%\section{Frozen orbitals for the Four-Index Transformation}
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%
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%In most cases, the frozen orbitals will be specified by the input for the
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%MP2 calculation (or calculation in some other module???) that invokes the
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%four-index transformation module. However, the user can specify frozen
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%orbitals separately for the four-index transformation, using \verb+SET+
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%directives of the form,
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%
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%\begin{verbatim}
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% set "fourindex:occ_frozen" \
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% <integer frozen_occupied default 0>
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% set "fourindex:vir_frozen" \
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% <integer frozen_virtual default 0>
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%\end{verbatim}
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%
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%The value specified for the integer variable \verb+frozen_occupied+
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%designates the lowest frozen occupied orbital. The value specified
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%for the integer variable \verb+frozen_virtual+ designates the highest
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%virtual frozen orbital. The default is zero for both of these variables,
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%which specifies no additional frozen orbitals for the four-index
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%transformation module.
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%
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%% Setting these parameters
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%% should not be required in the usual circumstances since these are
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%% determined by the calling modules, (see section \ref{sec:mp2}).
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%
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%
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%
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