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Subject: [ublas] Optimize: how to speed up prod?
From: Reich, Darrell (DARRELL.REICH_at_[hidden])
Date: 2013-10-04 12:52:34



So far my code below has been unable to beat the Fortran 77 program
benchmark using a quad core i7. I suspect the boost experts on this list
can offer some advice on how to best utilize the library for this
specific scenario (data described below) with a quick review of the code
extracted below.


While debugging this, I get unexpected results from M.filled1(),
M.filled2() when compared to M.size1() and M.size2(). I expected that
filled/size * 100 = % filled but filled2 > size2? v.filled and v.size
are what I expected.


When I switch compressed_vector to vector, the code crashes. I had to
remove the debug print for v.filled since vector does not implement it.
I assume here filled = size.


When I switch to column major form (code commented out below) it takes
longer. I suspect that is no surprise.


I'm sure it is time to go from basic boost to advanced. Thanks! We're
using version 1.54.


Extra credit: I'm sure there is an optimized way to do the += and the
copy too?


I tried noalias(v2) = prod(M,v1) but it crashes with the example below.

I tried writing my own product function using iterators but it crashes

Boost FOREACH looks interesting but I can't find an example for a Matrix
and why rewrite prod if we don't have to

I think Plan A get boost prod working faster versus Plan B replace prod
with rewritten product if the best if you have any suggestions on what I
could do better. Thanks!


Visual Studio C++ 2012 compiler settings for Win32 build on Windows 7

/Yu"StdAfx.h" /MP /GS /GL /analyze- /W3 /Gy- /Zc:wchar_t /Zi /Gm /O2
/Ob2 /Fd"Release\vc100.pdb" /fp:fast /D "WIN32" /D "NDEBUG" /D
"UNICODE" /errorReport:prompt /WX- /Zc:forScope /Gd /Oy- /Oi /MT
/Fa"Release\" /EHsc /nologo /Fo"Release\" /Ot /Fp"Release\Test.pch"


#include "stdafx.h" // copied all boost includes into this pre-compiled
header file

#include <boost/numeric/ublas/matrix.hpp>

#include <boost/numeric/ublas/matrix_sparse.hpp>

#include <boost/numeric/ublas/matrix_expression.hpp>

#include <boost/numeric/ublas/matrix_proxy.hpp>

#include <boost/numeric/ublas/vector.hpp>

#include <boost/numeric/ublas/vector_sparse.hpp>

#include <boost/numeric/ublas/vector_expression.hpp>

#include <boost/numeric/ublas/vector_proxy.hpp>

#include <boost/numeric/ublas/lu.hpp>

#include <boost/numeric/ublas/io.hpp>


// make release build faster

#ifdef NDEBUG




struct VECTOR


   std::vector<boost::numeric::ublas::compressed_vector<float>> vectors;



std::vector<boost::numeric::ublas::compressed_matrix<float>> theMatrix;

boost::numeric::ublas::column_major>> theMatrix;

std::vector<VECTOR> v1;

std::vector<VECTOR> v2;

// ...

ilen = 22;

jlen = 2;

xlen = 250;

ylen = 250;

n = xlen * ylen; // size = 64,000




// ...



// ...

theMatrix[i].resize(n,n); // sparse ~7 diagonals filled

v1[i].vectors.resize(n); // starts sparse, ends filled


// ...

theMatrix[i](j,k) = x; // load matrix once

// ...

v2[i].vectors[j] = prod(theMatrix[i], v1[i].vectors[j]);

// ...

v2[i].vectors[j](k) += datapoint; // add more to vector each time

// ...

// copy values back to save for next time step...

for (int i = 0; i < ilen; i++)


   for (int j = 0; j < jlen; j++)


         v1[i].vectors[j] = v2[i].vectors[j];