Simplify/fix adaptive hashmap #39988
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GuillaumeGomez
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Feb 22, 2017
Simplify/fix adaptive hashmap Please see rust-lang#38368 (comment) for context. The shift length math is broken. It turns out that checking for the shift length is complicated. Using simulations it's possible to see that a value of 2000 will only get probabilities down to ~1e-7 when the hashmap load factor is 90% (rust goes up to 90.9% as of today). That's probably not good enough to go into the stdlib with pluggable hashers. So this PR simplify the adaptive behavior to only consider displacement, which is much safer and very useful by itself. There's two comments because one of them is already being tested to be merged by bors.
frewsxcv
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Feb 23, 2017
Simplify/fix adaptive hashmap Please see rust-lang#38368 (comment) for context. The shift length math is broken. It turns out that checking for the shift length is complicated. Using simulations it's possible to see that a value of 2000 will only get probabilities down to ~1e-7 when the hashmap load factor is 90% (rust goes up to 90.9% as of today). That's probably not good enough to go into the stdlib with pluggable hashers. So this PR simplify the adaptive behavior to only consider displacement, which is much safer and very useful by itself. There's two comments because one of them is already being tested to be merged by bors.
eddyb
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Feb 25, 2017
Simplify/fix adaptive hashmap Please see rust-lang#38368 (comment) for context. The shift length math is broken. It turns out that checking for the shift length is complicated. Using simulations it's possible to see that a value of 2000 will only get probabilities down to ~1e-7 when the hashmap load factor is 90% (rust goes up to 90.9% as of today). That's probably not good enough to go into the stdlib with pluggable hashers. So this PR simplify the adaptive behavior to only consider displacement, which is much safer and very useful by itself. There's two comments because one of them is already being tested to be merged by bors.
eddyb
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Feb 25, 2017
Simplify/fix adaptive hashmap Please see rust-lang#38368 (comment) for context. The shift length math is broken. It turns out that checking for the shift length is complicated. Using simulations it's possible to see that a value of 2000 will only get probabilities down to ~1e-7 when the hashmap load factor is 90% (rust goes up to 90.9% as of today). That's probably not good enough to go into the stdlib with pluggable hashers. So this PR simplify the adaptive behavior to only consider displacement, which is much safer and very useful by itself. There's two comments because one of them is already being tested to be merged by bors.
bors
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Feb 25, 2017
Rollup of 28 pull requests - Successful merges: #39859, #39864, #39888, #39903, #39905, #39914, #39945, #39950, #39953, #39961, #39980, #39988, #39993, #39995, #40019, #40020, #40022, #40024, #40025, #40026, #40027, #40031, #40035, #40037, #40038, #40064, #40069, #40086 - Failed merges: #39927, #40008, #40047
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Please see #38368 (comment) for context.
The shift length math is broken. It turns out that checking for the shift length is complicated. Using simulations it's possible to see that a value of 2000 will only get probabilities down to ~1e-7 when the hashmap load factor is 90% (rust goes up to 90.9% as of today). That's probably not good enough to go into the stdlib with pluggable hashers.
So this PR simplify the adaptive behavior to only consider displacement, which is much safer and very useful by itself.
There's two comments because one of them is already being tested to be merged by bors.