This is a template for linear probing hash tables. Because this is a
probing hash table, one can only insert or modify entries (i.e. no
deletion). And there must be one invalid key __KEY_NIL that is used
to mark unused buckets. The advantages (vs. Go's own map type) are:
- All entries are stored in a single slice;
- Memory footprint is generally smaller;
- Look-up can be often faster or not much slower.
To customize,
- Define your own key, value types, etc. in
probing_params.go; - Replace
__inprobing_params.goandprobing_impl.gowith name of your choice; - Copy these two files to your project and you are good to go!
Public Domain: To the extent possible under law, Ke Wu has waived all copyright and related or neighboring rights to A linear probing hash map template in Go.
Summary: the probing hash table is,
- Slightly slower with much smaller memory footprint;
- Significantly faster with comparable memory usage;
- Faster on larger maps.
$ for s in 1.5 2; do for k in 1000 1000000 10000000; do go test -bench=. -gcflags='-l -l -l -l -l' -keys=$k -scale=$s; done; done
PASS
BenchmarkGoMapSpeed 20000 72026 ns/op
BenchmarkProbingMapSpeed 20000 78436 ns/op
BenchmarkGoMapMem 0 0 ns/op
--- BENCH: BenchmarkGoMapMem
probing_bench_test.go:143: go-map: 0.04MB
BenchmarkProbingMapMem 0 0 ns/op
--- BENCH: BenchmarkProbingMapMem
probing_bench_test.go:127: probing: 1000 keys; 1500 buckets; load factor 0.67
probing_bench_test.go:143: probing: 0.02MB
ok github.com/kho/probing 4.561s
PASS
BenchmarkGoMapSpeed 10000 115136 ns/op
BenchmarkProbingMapSpeed 10000 110323 ns/op
BenchmarkGoMapMem 0 0 ns/op
--- BENCH: BenchmarkGoMapMem
probing_bench_test.go:143: go-map: 36.58MB
BenchmarkProbingMapMem 0 0 ns/op
--- BENCH: BenchmarkProbingMapMem
probing_bench_test.go:127: probing: 1000000 keys; 1500000 buckets; load factor 0.67
probing_bench_test.go:143: probing: 22.89MB
ok github.com/kho/probing 5.609s
PASS
BenchmarkGoMapSpeed 10000 137659 ns/op
BenchmarkProbingMapSpeed 10000 131698 ns/op
BenchmarkGoMapMem 0 0 ns/op
--- BENCH: BenchmarkGoMapMem
probing_bench_test.go:143: go-map: 303.56MB
BenchmarkProbingMapMem 0 0 ns/op
--- BENCH: BenchmarkProbingMapMem
probing_bench_test.go:127: probing: 10000000 keys; 15000000 buckets; load factor 0.67
probing_bench_test.go:143: probing: 228.88MB
ok github.com/kho/probing 38.949s
PASS
BenchmarkGoMapSpeed 20000 73367 ns/op
BenchmarkProbingMapSpeed 20000 64460 ns/op
BenchmarkGoMapMem 0 0 ns/op
--- BENCH: BenchmarkGoMapMem
probing_bench_test.go:143: go-map: 0.04MB
BenchmarkProbingMapMem 0 0 ns/op
--- BENCH: BenchmarkProbingMapMem
probing_bench_test.go:127: probing: 1000 keys; 2000 buckets; load factor 0.50
probing_bench_test.go:143: probing: 0.03MB
ok github.com/kho/probing 4.167s
PASS
BenchmarkGoMapSpeed 10000 115724 ns/op
BenchmarkProbingMapSpeed 20000 89159 ns/op
BenchmarkGoMapMem 0 0 ns/op
--- BENCH: BenchmarkGoMapMem
probing_bench_test.go:143: go-map: 36.59MB
BenchmarkProbingMapMem 0 0 ns/op
--- BENCH: BenchmarkProbingMapMem
probing_bench_test.go:127: probing: 1000000 keys; 2000000 buckets; load factor 0.50
probing_bench_test.go:143: probing: 30.52MB
ok github.com/kho/probing 7.349s
PASS
BenchmarkGoMapSpeed 10000 137724 ns/op
BenchmarkProbingMapSpeed 10000 100151 ns/op
BenchmarkGoMapMem 0 0 ns/op
--- BENCH: BenchmarkGoMapMem
probing_bench_test.go:143: go-map: 303.51MB
BenchmarkProbingMapMem 0 0 ns/op
--- BENCH: BenchmarkProbingMapMem
probing_bench_test.go:127: probing: 10000000 keys; 20000000 buckets; load factor 0.50
probing_bench_test.go:143: probing: 305.18MB
ok github.com/kho/probing 37.895s