Update docs

Author: filikat

docs/src/parallel.md

@@ -57,9 +57,10 @@ If the [parallel](@ref option-parallel) option is set "choose", the solver selec
 level to use based on a heuristic. When the [parallel](@ref option-parallel) option is set 
 "choose" or "off", the value of the hipo\_parallel\_type option is ignored.
 
-If the [parallel](@ref option-parallel) option is set to "on" or "choose", HiPO uses 
-multiple threads to run multiple orderings and Newton system approaches in parallel, in 
-order to select the best one.
+In addition, HiPO utilises parallelism to run multiple orderings heuristics on different 
+Newton system approaches (in order to choose the best one), and to construct the normal 
+equations matrix. This parallelism is always advantageous, so is performed regardless of 
+the value of the [parallel](@ref option-parallel) option.
 
 The extent to which parallelism is used in HiPO depends on the value of the
 [threads](@ref option-threads) option (see above).