[ojAlgo-user] Populating matrices

[Nigel S. <nig...@gm...>]

Hi, I wonder if someone could please comment on the proper way to
populate blank matricies, with memory efficiency in mind.

The example I have is loading a CSV file into the matrix. Previously I
used JAMA:
1) Created the matrix (new Matrix(rowCount, colCount))
2) Iterate over the rows:
2.1)   Iterate over the columns
2.1.1) Write to the array (currentMatrix.set(row, j,
Double.parseDouble(cols[remainingCols.get(j)]));)

I adapted this to ojalgo, so now I use
1) PrimitiveMatrix.FACTORY.buildZero(rowCount, colCount)
...
2.1.1) currentMatrix = currentMatrix.set(row, j,
Double.parseDouble(cols[colsOfInterest[j]]));

This is very slow, in that the JAMA version takes 0.3 s to run, and
the ojalgo version takes 30+ seconds to run. Essentially because the
matrix set method seems to make a copy of the matrix, which it
returns. This does seem at odds with the java doc which indicates that
the physical stores are mutable, so I would assume the matrix should
also be mutable.

The other option appears to be to create a double array and copy it
into the matrix with the factory, but this will mean, for a short
time, there will be two copies of a potentially large array in memory.

Any advice would be most helpful.

Cheers
Nigel