=============================================
Using FLENS-BLAS through Overloaded Operators                            [TOC]
=============================================

Toy Example
===========
We use the same example as before, i.e. we compute $y = \beta y + \alpha\,A^T x
+ z$ where $\alpha, \beta$ are scalars, $x, y, z$ are (dense) vectors and $A$
is a (general) matrix (with full storage).

This time we just code it the natural way, i.e. as
`y = beta*y + alpha*transpose(A)*x + z` and hope the best.

However, afterwards we want to check how __FLENS-BLAS__ was internally utilized
for the evaluation of the linear algebra expression.  We therefore log the
evaluation.


Example Code
============
:import: flens/examples/tut02-page03-example.cc [stripped, downloadable]

Comments on Example Code
========================
:import: flens/examples/tut02-page03-example.cc [brief]


Compile, Run and Examining the Log-File
=======================================

Compiling the code becomes slightly more complex.  But we hope the comments
give enough glues to see what need to be done.

   *--[SHELL]---------------------------------------------------------------*
   |                                                                        |
   |  cd flens/examples                                                     |
   |  #                                                                     |
   |  # cleanup old object files and compile some stuff needed for logging  |
   |  #                                                                     |
   |  rm -f *.o                                                             |
   |  g++ -Wall -std=c++11 -I../.. -c ../../flens/debug/auxiliary/*.cc      |
   |  #                                                                     |
   |  # compile with -DFLENS_DEBUG_CLOSURES and link against the log stuff  |
   |  #                                                                     |
   |  g++ -Wall -std=c++11 -I../.. *.o tut02-page03-example.cc              |
   |  ./a.out                                                               |
   |  #                                                                     |
   |  # look what is in the log file                                        |
   |  #                                                                     |
   |  cat mylogfile                                                         |
   |                                                                        |
   *------------------------------------------------------------------------*

In the log files you see a complete trace of function calls.  If you compile
with `-DNDEBUG` instead most of these functions get inlined and only the
functions marked with the arrows `-->` actually get called.  Not that this
means that in *non-debug mode* the resulting code is equivalent to calling
CXXBLAS directly.

Note: The logging mechanism in FLENS gives different matrix/vector objects
unique names.  The letter represents the matrix/vector types:

   +--------+--------------------+
   | Letter | Matrix/Vector Type |
   +--------+--------------------+
   | `x`    | `DenseVector`      |
   +--------+--------------------+
   | `A`    | `GeMatrix`         |
   +--------+--------------------+
   | `T`    | `TrMatrix`         |
   +--------+--------------------+
   | `S`    | `SyMatrix`         |
   +--------+--------------------+

Further, vectors and matrices of same type receive subsequent numbers (like in
this example vectors receive names `x1`, `x2`, `x3`).

:links: __FLENS-BLAS__  -> doc:flens/blas/blas

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