[Issue 19075] New: rt.util.random.Rand48.defaultSeed should prefer RDTSC or mach_absolute_time to ctime.time
d-bugmail at puremagic.com
d-bugmail at puremagic.com
Wed Jul 11 01:45:11 UTC 2018
https://issues.dlang.org/show_bug.cgi?id=19075
Issue ID: 19075
Summary: rt.util.random.Rand48.defaultSeed should prefer RDTSC
or mach_absolute_time to ctime.time
Product: D
Version: D2
Hardware: x86_64
OS: All
Status: NEW
Severity: enhancement
Priority: P1
Component: druntime
Assignee: nobody at puremagic.com
Reporter: n8sh.secondary at hotmail.com
`rt.util.random.Rand48.defaultSeed` generates a seed from the clock using
`ctime.time`. With `D_InlineAsm_X86_64` it would be better to use the `rdtsc`
instruction because it is much faster as well as being finer precision. (Finer
precision is a benefit not because we care about accurate time, but because the
differences between seeds generated this way are potentially greater.) The same
is true of `mach_absolute_time` on macOS. The Microsoft Windows equivalent
would be `QueryPerformanceCounter` but I haven't benchmarked it to verify that
it is faster than `ctime.time`.
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