# Speeding up Calculations

If a calculation seems to be taking a long time, consider adjusting
the following settings. Note that some of these can result in
misleading calculations under the "wrong" circumstances.

- Make sure
`PrintLevel`
is `Minimal` or `None` and `ShowEstUnc` is off.
Leaving either of these on can produce a lot of output in the
(possibly hidden) log window which is time consuming to
calculate and print.

- Turning
`AutoReplot`
off will stop automatic recalculation of the spectrum; an
explicit press of the simulate button is then required for a
calculation.

- Is the range of
*J* calculated more than required?
Consider:
- Reducing the range of
*J* values calculated - see Determining J ranges
- Reducing the range of
*J *used in calculating the
partition function; turn AutoQConverge
off.
- Not calculating the partition function at all - set IntensityUnits
to Arbitrary.

- The
`NoLineList`
setting will disable the use of saved line lists for simulation;
turning this on will use less memory, but at the expense of more
calculation when a spectrum is simulated.
- If the program runs out of memory, consider the 64 bit
version.
- If calculating hyperfine structure,setting
`MaxDJ` for
Linear, Symmetric or Asymmetric Top nuclei to
zero can give significantly faster calculations but may be less
accurate, particularly for low *J* or large hyperfine
structure.
- Adjusting the number of threads used for the calculation
("View", "Threads") may help for some calculations. Use the
operating system task manager or system monitor to see how
effective the parallel calculation is; ideally all the CPU's
should be operating at 100%, but some calculations may benefit
from a smaller number of threads, or only a single thread.
"View", "Timing" will give an indication as to where the time is
being spent; if it is in matrix diagonalization then the only
way to speed the calculation is reducing the size of the
problem.