On Nov 30, 2007 12:03 PM, nisha kannookadan <nishak44@hotmail.com> wrote:

Hey everybody

Finally I got to the ublas mailing list and I hope u guys can help me.
Im quite new with boost and everything else than an expert.

Im programming in C++ and have to translate a program from matlab
to C++. I did it, but my program is way to slow.

I got already suggestions from the boost users and developpers:
- to do pass by refernce
- define DNDEBUG
- to compile with full optimization
- to use bindings (but I dont think, I need it, since its not high level matrix stuff)
- and that I should go to post the question here :).

I did some of the changes already and it got little better, but its still bad.

The program is quite huge, so I took a part out of it, which is now even runnable
for you.
I post here the maltab and c++ code, so u maybe can help me.

So first C++:

#include
#include "MVHF.h"
#include
#include
#include
#include
#include

#define DNDEBUG
#include

using namespace std;

void ttrans(matrix& At, int level)
{
matrix cfe1, cfe2, cfo, cfe, c, d;
int N,s2;

N = (At.size1()+1)/2;
s2 = At.size2 ();
zero_matrix zer(N,s2);

for (int ii = 1; ii <= level; ii++)
{

cfo = subslice(At, 0,2,N, 0,1,s2);
cfe = subslice(At, 1,2,N-1, 0,1,s2);

c = cfe + (subrange(cfo, 0,N-1, 0,s2)+subrange(cfo, 1,N, 0,s2))*0.5;

zer.resize(N,s2,true);
cfe1 = zer;
cfe2 = zer;

(subrange(cfe1, 0,N-1, 0,s2)).assign(cfe);
(subrange(cfe2, 1,N, 0,s2)).assign(cfe);
d = cfo-(cfe1+cfe2)*0.5;

(subrange(At, 0,N-1, 0,At.size2())).assign(c);
(subrange(At, N-1,2*N-1, 0,At.size2 ())).assign(d);

N = N/2;
}

}

void init(int dom,int llev)
{

int in_dofs_LA= 511;
matrix Am_LA, As_LA;
double mesh_size = ((double)(dom)/(in_dofs_LA+1));

scalar_matrix zer(in_dofs_LA, in_dofs_LA,0.0);
Am_LA.resize(in_dofs_LA, in_dofs_LA, false);
As_LA.resize(in_dofs_LA, in_dofs_LA, false);
Am_LA.assign(zer);
As_LA.assign(zer);

Am_LA(0,0) = 4.0;
Am_LA(1,0) = 1.0;

As_LA(0,0) = 2.0;
As_LA(1,0) = -1.0;

for (int ii = 1; ii < (in_dofs_LA-1); ii++){
Am_LA(ii-1,ii) = 1.0;
Am_LA(ii,ii) = 4.0;
Am_LA(ii+1,ii) = 1.0;

As_LA(ii-1,ii) = -1.0;
As_LA(ii,ii) = 2.0;
As_LA(ii+1,ii) = -1.0;
}

Am_LA(in_dofs_LA-2,in_dofs_LA-1) = 1.0;
Am_LA(in_dofs_LA-1,in_dofs_LA-1) = 4.0;

As_LA(in_dofs_LA-2,in_dofs_LA-1) = -1.0;
As_LA(in_dofs_LA-1,in_dofs_LA-1) = 2.0;

Am_LA = Am_LA*(mesh_size/6.0);
As_LA = As_LA*(1.0/mesh_size);

ttrans(Am_LA,llev);
Am_LA = trans(Am_LA);
ttrans(Am_LA,llev);
Am_LA = trans(Am_LA);

ttrans(As_LA,llev);
As_LA = trans(As_LA);
ttrans(As_LA,llev);
As_LA = trans(As_LA);

}

int main() {
clock_t start, end;
start = clock();

init(1,8);
end = clock();

std::cout << " " << std::endl;
std::cout << "Elapsed time is " << (double)(end-start)/CLOCKS_PER_SEC << "." << std::endl;
}

Here the matlab version of it:

function test()
tic
R = 1;
L = 8;
n = 2^(L+1)-1;
h = R/(n+1);

e = ones(n,1);
Am = h/6*spdiags([e, 4*e, e], -1:1, n, n);

% compute stiffness matrix
As = 1/h*spdiags([-e, 2*e, -e], -1:1, n, n);

% transform into wavelets
Am = ttrans(ttrans(Am,L)',L)';
As = ttrans(ttrans(As,L)',L)';
toc

return

function cd = ttrans(cl,L)
N = size(cl,1)+1;
N = N/2;

m = size(cl,2);

z = zeros(1,m);
cd = cl;
for i=1:L
cfo = cd(1:2:2*N-1,:);
cfe = cd(2:2:2*N-2,:);

% wavelets
c = cfe + (cfo(1:end-1,:)+cfo(2:end,:))/2;
d = cfo - ([cfe;z]+[z;cfe])/2;

cd(1:2*N-1,:) = [c;d];
N = N/2;
end

return

Id be so thankful for any help.
Bye
Nisha K
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