# 4.68 FAQ-1135 Why is speed slower when loop increases?

Last Update: 5/6/2022

Each loop is slower when number of loop increases if add columns and set designation take time when number of columns in the existing sheet is large:

//[Book1]1! already has 2450x3 columns
rw=2450;
sec;
loop (tt,1,50)
{
ncol = rw*3;

//access non-existent column, so it will add column
range dis3=[Book1]1!col($(ncol+1)); range vel3=[Book1]1!col($(ncol+2));
range vel3a=[Book1]1!col($(ncol+3)); dis3[L]$=f$(tt)dis; vel3[L]$=f$(tt)vel; vel3a[L]$=f$(tt)vela; //set designation take time when number of columns in the existing sheet is large dis3.type=4; vel3.type=1; vel3a.type=1; rw=rw+1; }; So we need to try to avoid above actions inside a loop, i.e. prepare the whole worksheet first before the loop: int nloop = 50; //specify the worksheet range rWa = [Book4]1!; int oldcol = rWa.nCols; //add columns rWa.nCols = rWa.nCols + nloop*3; //set designations coldesig desig:=X2Y rng:=%(rWa)$(oldcol+1):$(rWa.nCols); loop (tt,1,nloop) { range dis3=%(rWa)$(oldcol+3*tt-2);
range vel3=%(rWa)$(oldcol+3*tt-1); range vel3a=%(rWa)$(oldcol+3*tt);

dis3[L]$=f$(tt)dis;
vel3[L]$=f$(tt)vel;
vel3a[L]$=f$(tt)vela;

}

Keywords:LabTalk, loop