var asp, bsp: TSparseMtx; csp, dsp: TSparseMtx; d: Vector; begin // ... // #1 : split asp into lower(bsp), upper(csp) and diagonal(d) sections bsp.LowerTriangle(asp); csp.UpperTriangle(asp); asp.Diag(d); // now combine lower(bsp), upper, and diagonal(d) back dsp.AddSplit(bsp,d,csp); // should be equal if not asp.Equal(dsp) then Eraise('Not Equal!'); end;