[#bsl-unordered_set-0d2d-reserve]
= xref:bsl.adoc[bsl]::xref:bsl/unordered_set-0d2d.adoc[unordered_set]::reserve
:relfileprefix: ../../
:mrdocs:

Reserve capacity for at least `numElements` elements.

== Synopsis

Declared in `<bslstl_unorderedset.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
void
reserve(xref:bsl/unordered_set-0d2d/size_type.adoc[size_type] numElements);
----

== Description

Increase the number of buckets of this set to a quantity such that the ratio between the specified `numElements` and this quantity does not exceed `max_load_factor`. Note that this guarantees that, after the reserve, elements can be inserted to grow the container to `size() == numElements` without rehashing. Also note that memory allocations may still occur when growing the container to `size() == numElements`. Also note that this operation has no effect if `numElements <= size()`.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *numElements*
| number of elements to reserve capacity for
|===


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