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Special-case size-1 sequential hopscotch hash table

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Rather than allocate a HH_HOP_RANGE large array of buckets, allocate
just 1 if the initial size is 1, then jump to HH_HOP_RANGE as soon as a
second element is added to the table.  There are quite a few cases where
hash tables are created where there never be more than 1 (or even 0)
elements in the table (e.g., a writer without readers, a reader for a
keyless topic).

Signed-off-by: Erik Boasson <eb@ilities.com>
This commit is contained in:
Erik Boasson 2019-06-24 10:05:00 +02:00 • committed by eboasson
parent 0b8fd9fcc0
commit 0e888eb2ec
2 changed files with 55 additions and 29 deletions
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4
src/core/ddsc/src/dds_whc.c
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@ -366,11 +366,11 @@ struct whc *whc_new (int is_transient_local, uint32_t hdepth, uint32_t tldepth)
#if USE_EHH
whc->seq_hash = ddsrt_ehh_new (sizeof (struct whc_seq_entry), 32, whc_seq_entry_hash, whc_seq_entry_eq);
#else
whc->seq_hash = ddsrt_hh_new (32, whc_node_hash, whc_node_eq);
whc->seq_hash = ddsrt_hh_new (1, whc_node_hash, whc_node_eq);
#endif
if (whc->idxdepth > 0)
whc->idx_hash = ddsrt_hh_new (32, whc_idxnode_hash_key, whc_idxnode_eq_key);
whc->idx_hash = ddsrt_hh_new (1, whc_idxnode_hash_key, whc_idxnode_eq_key);
else
whc->idx_hash = NULL;