Thanks for your help - and info. It is good to hear that in the future the

sparse command will accept integer values rather than only double precision.

I have managed to improve the code I am working on but still have one major

bottleneck. Even though I have to perform operations such as a

Cholesky factorization and many matrix multiplications, my bottleneck is

with the following two lines

mat11=sparse(double(Ix), double(Jx), X(valuex),n^2,n*(n-1)/2);

mat11=mat11+sparse(double(Is), double(Js), Sy(values),n^2,n*(n-1)/2);

Here Ix,Jx,Is,Js,valuex,values are long vectors of indices and

X,Sy are sparse symmetric matrices n by n matrices.

Have I reached the limit in improving things within matlab? Should I be

looking at a mex file?

thanks for the advice

>Henry,

>If you can't store double precision i, j and values in the MATLAB

>workspace with storage requirements:

>3 * 8 * nnz(A)

>then you also can't store 32 bit integer/single precision i and j and

>double precision values AND the resulting sparse(A) with combined

>storage requirements:

>(2 * 4 + 8) * nnz(A) + (4+8)*nnz(A) + 4*(size(A,2)+1)

>However, we are considering accepting integer or single precision i

>and j sparse matrix indices in the sparse function S =

>sparse(i,j,vals) in a future release of MATLAB. (Internally the row

>indices and column pointers of the sparse matrix data structure are

>stored as 32 bit integers already).

>Penny Anderson

>The MathWorks, Inc.

>> I am using the command

>> A=sparse(I,J,values,m,n)

>> where the index sets I and J are very 'long' vectors.

>> Therefore, I would like to use

>> single arrays for I and J

>> to save memory. However, I then get the error message

>> ??? Error using ==> sparse

>> Function 'sparse' not defined for variables of class 'single'.

>> I have tried

>> A=sparse(double(I),double(J),values,m,n)

>> but this seems to still run into memory problems.

>> Is there a way to avoid this?

>> thanks for any hints/advice

>> --

>> Univ. of Waterloo |URL

>http://orion.math.uwaterloo.ca/~hwolkowi

>> Dept of Comb and Opt |Tel (519) 888-4567, x5589, office MC6065

>> Waterloo, Ont. CANADA N2L 3G1 |Fax (519) 725-5441

--

Univ. of Waterloo |URL http://orion.math.uwaterloo.ca/~hwolkowi

Dept of Comb and Opt |Tel (519) 888-4567, x5589, office MC6065

Waterloo, Ont. CANADA N2L 3G1 |Fax (519) 725-5441