So on Linux it's working as expected. In the playground time is "virtual";
the start time is fixed and it doesn't progress unless you explicitly Sleep
-- because you don't Sleep in your program, time.Now() returns the same
time on both invocation.
So the only slightly surprising part is that on Windows, time as measured
by time.Now() doesn't progress between the two statements. But I don't
think it is because Windows is so much faster than Linux. :) I'd guess this
is because the way Windows manages time is different from how Linux manages
it, and/or the way the time package implemented is different between
Windows and Linux. The result of the cross-platform differences seems to be
less precision on Windows -- at least in this specific scenario.
Peter
On Fri, May 4, 2018 at 9:33 PM, Andrei Avram <andrei.avram....@gmail.com>
wrote:
> Peter and Ian, you are both wright regarding the printing. Still, on Linux
> I have different values than on Go Playground.
>
> Regarding the speed, Peter, do you think that on Windows the two calls
> just run faster every time?
>
> On Friday, May 4, 2018 at 9:07:15 PM UTC+3, speter wrote:
>>
>> b is slightly less than 3 because there is a bit of time between the two
>> calls to time.Now().
>>
>> If you substitute this:
>> fmt.Printf("input: %20.18f\n", b)
>>
>> you get something like
>> input: 2.999999965553350911
>>
>> HTH
>> Peter
>>
>> On Fri, May 4, 2018 at 7:26 PM, Andrei Avram <andrei.a...@gmail.com>
>> wrote:
>>
>>> Hello everyone,
>>>
>>> Today I ran into a situation that is strange to me. I ran the following
>>> code on two Linux machines (go run floor.go), on two Windows ones, and on
>>> Go Playground.
>>>
>>> package main
>>>
>>> import (
>>> "time"
>>> "math"
>>> )
>>>
>>> func main() {
>>> datetime := time.Now().Add(time.Hour * 24 * 7 * 4 * 12 * 3)
>>> seconds := -1 * int(time.Now().Sub(datetime).Seconds())
>>> a := 29030400
>>> b := float64(seconds) / float64(a)
>>>
>>> println("input:", b)
>>> println("floor:", math.Floor(b))
>>> }
>>>
>>> On Linux the output is:
>>>
>>> input: +3.000000e+000
>>> floor: *+2.000000e+000*
>>>
>>> On Windows and Playground:
>>>
>>> input: +3.000000e+000
>>> floor: *+3.000000e+000*
>>>
>>> As you can see, on Linux the floor value of float value 3 is rounded
>>> down to 2, while on Windows/Playground it's 3.
>>>
>>> The code was ran with Go 1.10 and 1.10.2.
>>>
>>> The system details of one of the Linux machines, as reported by "go bug":
>>>
>>> go version go1.10.2 linux/amd64
>>> GOARCH="amd64"
>>> GOBIN=""
>>> GOCACHE="/home/msd/.cache/go-build"
>>> GOEXE=""
>>> GOHOSTARCH="amd64"
>>> GOHOSTOS="linux"
>>> GOOS="linux"
>>> GOPATH="/home/msd/go/"
>>> GORACE=""
>>> GOROOT="/usr/local/go"
>>> GOTMPDIR=""
>>> GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
>>> GCCGO="gccgo"
>>> CC="gcc"
>>> CXX="g++"
>>> CGO_ENABLED="1"
>>> CGO_CFLAGS="-g -O2"
>>> CGO_CPPFLAGS=""
>>> CGO_CXXFLAGS="-g -O2"
>>> CGO_FFLAGS="-g -O2"
>>> CGO_LDFLAGS="-g -O2"
>>> PKG_CONFIG="pkg-config"
>>> GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0
>>> -fdebug-prefix-map=/tmp/go-build304261270=/tmp/go-build
>>> -gno-record-gcc-switches"
>>> GOROOT/bin/go version: go version go1.10.2 linux/amd64
>>> GOROOT/bin/go tool compile -V: compile version go1.10.2
>>> uname -sr: Linux 4.13.0-37-generic
>>> Distributor ID: Ubuntu
>>> Description: Ubuntu 16.04.4 LTS
>>> Release: 16.04
>>> Codename: xenial
>>> /lib/x86_64-linux-gnu/libc.so.6: GNU C Library (Ubuntu GLIBC
>>> 2.23-0ubuntu10) stable release version 2.23, by Roland McGrath et al.
>>> gdb --version: GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.5) 7.11.1
>>>
>>>
>>> Is there something I miss or could this be an issue?
>>>
>>> Thanks,
>>> Andrei
>>>
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>>
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