+1 Thanks for taking this on Neil! — *Joris Van Remoortere* Mesosphere
On Fri, Feb 12, 2016 at 11:25 PM, Neil Conway <neil.con...@gmail.com> wrote: > tl;dr: > > If you use resource values with more than three decimal digits of > precision (e.g., you are launching a task that uses 2.5001 CPUs), > please speak up! > > ==== > > Mesos uses floating point to represent scalar resource values, such as > the number of CPUs in a resource offer or dynamic reservation. The > master does resource math in floating point, which leads to a few > problems: > > * due to roundoff error, frameworks can receive offers that have > unexpected resource values (e.g., MESOS-3990) > * various internal assertions in the master can fail due to roundoff > error (e.g., MESOS-3552). > > In the long term, we can solve these problems by switching to a > fixed-point representation for scalar values. However, that will > require a long deprecation cycle. > > In the short term, we should make floating point behavior more > reliable. To do that, I propose: > > (1) Resource values will support AT MOST three decimal digits of > precision. Additional precision in resource values will be discarded > (via rounding). > > (2) The master will internally used a fixed-point representation to > avoid unpredictable roundoff behavior. > > For more details, please see the design doc here: > > https://docs.google.com/document/d/14qLxjZsfIpfynbx0USLJR0GELSq8hdZJUWw6kaY_DXc > -- comments welcome! > > Thanks, > Neil >
