#9251: ghc does not expose branchless max/min operations as primops -------------------------------------+------------------------------------ Reporter: carter | Owner: carter Type: task | Status: new Priority: normal | Milestone: 7.10.1 Component: Compiler | Version: 7.8.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: #9246 -------------------------------------+------------------------------------ Comment (by arotenberg): Yeah, I've seen those slides before. The problem with the arguments presented is that I know there is a class of users who demands "linguistically-legislated exact reproducibility" for floating-point computations, because I'm part of it! For my day job, I use Java to write a tool for modeling safety-critical software systems on desktop hardware. For our purposes, it is ''far'' more important that the results of the simulation be exactly identical across different platforms than it is they be numerically accurate or efficiently computable. We use Java's `strictfp` keyword and `StrictMath` class ubiquitously in our simulation engine, because it is essential that the output of our program be identical, no matter where or when it is run. When it is necessary to compute different or more numerically-accurate floating-point outputs, we emulate it in software. This is slow but allows us 100% confidence that you will always get the same results. That said, our application is a rare case. In most situations, faster and more accurate computations that can give slightly different results on different machines are preferable to calculations that are wrong in exactly-reproducible ways. Which section (if any) of the Haskell 2010 Report specifies the behavior of floating-point operations? I've glanced through it quickly but all I've been able to find is [https://www.haskell.org/onlinereport/haskell2010/haskellch9.html#x16-1710009 the Prelude definitions of the instances for Float and Double], which just list them as primitives. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9251#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler