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Posted to dev@brpc.apache.org by GitBox <gi...@apache.org> on 2019/12/30 04:19:06 UTC
[GitHub] [incubator-brpc] pexeer opened a new pull request #1009: bugfix to
the hash function HashInts32.
pexeer opened a new pull request #1009: bugfix to the hash function HashInts32.
URL: https://github.com/apache/incubator-brpc/pull/1009
the another optional solution of Issue #1007
make right of the hash function of HashInts32.
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[GitHub] [incubator-brpc] pexeer commented on a change in pull request
#1009: bugfix to the hash function HashInts32.
Posted by GitBox <gi...@apache.org>.
pexeer commented on a change in pull request #1009: bugfix to the hash function HashInts32.
URL: https://github.com/apache/incubator-brpc/pull/1009#discussion_r364665770
##########
File path: src/butil/containers/hash_tables.h
##########
@@ -129,8 +129,10 @@ using BUTIL_HASH_NAMESPACE::hash_set;
//
// Contact danakj@chromium.org for any questions.
inline std::size_t HashInts32(uint32_t value1, uint32_t value2) {
- uint64_t value1_64 = value1;
- uint64_t hash64 = (value1_64 << 32) | value2;
+ uint64_t short_random1 = 842304669U;
+ uint64_t short_random2 = 619063811U;
+
+ uint64_t hash64 = short_random1 * value1 + short_random2 * value2;
Review comment:
good idea!
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[GitHub] [incubator-brpc] jamesge merged pull request #1009: bugfix to the
hash function HashInts32.
Posted by GitBox <gi...@apache.org>.
jamesge merged pull request #1009: bugfix to the hash function HashInts32.
URL: https://github.com/apache/incubator-brpc/pull/1009
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[GitHub] [incubator-brpc] jamesge commented on a change in pull request
#1009: bugfix to the hash function HashInts32.
Posted by GitBox <gi...@apache.org>.
jamesge commented on a change in pull request #1009: bugfix to the hash function HashInts32.
URL: https://github.com/apache/incubator-brpc/pull/1009#discussion_r362367108
##########
File path: src/butil/containers/hash_tables.h
##########
@@ -129,8 +129,10 @@ using BUTIL_HASH_NAMESPACE::hash_set;
//
// Contact danakj@chromium.org for any questions.
inline std::size_t HashInts32(uint32_t value1, uint32_t value2) {
- uint64_t value1_64 = value1;
- uint64_t hash64 = (value1_64 << 32) | value2;
+ uint64_t short_random1 = 842304669U;
+ uint64_t short_random2 = 619063811U;
+
+ uint64_t hash64 = short_random1 * value1 + short_random2 * value2;
Review comment:
please use [fmix64](https://github.com/apache/incubator-brpc/blob/fc07b7bf45c4b2aa90ae5c832f3b48a8da124640/src/butil/third_party/murmurhash3/murmurhash3.h#L57)((value1_64 << 32) | value2) which is better studied.
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