: [[image:iciclesimage]]

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== Dealing With Large Candidate Sets ==

One of the advantages '''Icicles''' provides is the ability to deal with
large sets of [[completion]] candidates with ease.  There are other
libraries that also let you [[Icicles - Cycling Completions|cycle]] among various choices of
different kinds ([[buffer]]s, files, and so on), but cycling quickly
loses its effectiveness as the number of candidates increases. 

'''Icicles''' [[apropos completion|apropos]] matching lets you work with a large initial set of
candidates by filtering them, quickly reducing the number
candidates to cycle through.  Until you get used to '''Icicles''', you will be surprised at your
ability to manipulate even humongous sets of choices.

Nevertheless, there can be times when a candidate set is so large
that you need to use a few tricks to deal with it efficiently.
There are ''two main things that take time'' when dealing with a large
set: ''computing'' the set and ''displaying'' it (with highlighting) in buffer `*Completions*'.
In particular, ''[[Icicles - Icompletion|incremental completion]]'' display is costly because it
does both of these, recompute the set and redisplay it, each time you type or delete a character in the [[minibuffer]].

Here are some tips to improve performance with a large set of candidates:

* ''Turn off [[IcompleteMode|Icomplete mode]]''.  You can use '''`<tt>C-M-#</tt>'''' in the minibuffer to do this anytime.

* ''Turn off candidate [[Icicles - Sorting Candidates|sorting]]'', or avoid sort orders that are particularly costly.  Use '''`##C-,##'''' to change the sort order or turn sorting off.

* Tell particular '''Icicles''' [[multi-command]]s to turn off [[incremental completion or Icomplete mode, by giving their symbols property
'''`icicle-turn-off-incremental-completion'''' or
'''`icicle-turn-off-icomplete-mode''''.

* Compute a large candidate set only once,
   ''cache'' the result, and reuse it later by reading the cache
   instead of recomputing.  This is useful, for instance, for the
   candidate set of all files on your file system.  You can cache
   a set of candidates in either a [[variable]] (quickest, but not
   persistent) or a disk file (slower, persistent).  See
   [[Icicles - Persistent Completions]].

* Compute a large candidate set (and perhaps cache it or filter it)
   ''without displaying'' it in `*Completions*', by using '''`C-M-TAB'''' (`C-M-tab') or
   '''`C-M-S-TAB'''' (`C-M-S-tab') instead of `TAB' or `S-TAB', respectively.  These
   are bound to commands '''`icicle-prefix-complete-no-display'''' and
   '''`icicle-apropos-complete-no-display''''.  For example, when
   initially computing the set of all files on your file system
   for `C-u M-x icicle-locate-file', use `C-M-S-TAB' to compute
   the set, then use `##C-}##' to save it to a cache file -- you need
   never display it.


: (The documentation refers to the keys that do this as
`C-M-S-TAB' and `C-M-TAB'.  Actually, this is only by default.
You can customize this, using [[option]]s
'''`<tt>[[Icicles - Customization and General Tips#icicle-apropos-complete-no-display-keys|icicle-apropos-complete-no-display-keys]]</tt>'''' and
'''`<tt>[[Icicles - Customization and General Tips#icicle-prefix-complete-no-display-keys|icicle-prefix-complete-no-display-keys]]</tt>''''.)


'''See Also:'''

* [[Icicles - Icompletion]] for information about incremental completion and Icomplete mode

* [[Icicles - Sorting Candidates]]  for information about sorting candidates

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DrewsElispLibraries referenced here: Lisp:icicles.el

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