Just got with all.bash at tip:
# GOMAXPROCS=2 runtime -cpu=1,2,4
--- FAIL: TestMapIterOrder-2 (0.00s)
map_test.go:437: Map with n=9 elements had consistent iteration order: [0 1 2 3 4 5 6 7 8]
FAIL
FAIL runtime 19.833s
To reproduce:
go test -run MapIterOrder -cpu=$(perl -e 'print "1,"x300') -v
always fails at least once.
The hash function is picking the same hash bit for all 9 values (1 in 512 chance). Then
instead of having two buckets we'd have one bucket plus an overflow bucket.
Right now the iterator either picks a random bucket or picks a random offset within a
single bucket.
I think it should do both: pick a random bucket and pick a random offset, and start at
that offset (and wrap) in every bucket.
