digitalmars.D.bugs - [Issue 20451] New: comparing identical floating points does not work
- d-bugmail puremagic.com (52/52) Dec 15 2019 https://issues.dlang.org/show_bug.cgi?id=20451
https://issues.dlang.org/show_bug.cgi?id=20451 Issue ID: 20451 Summary: comparing identical floating points does not work on Win32 and FreeBSD32. Product: D Version: D2 Hardware: Other OS: Windows Status: NEW Severity: normal Priority: P1 Component: dmd Assignee: nobody puremagic.com Reporter: bugzilla d-ecke.de Evolving from issue 5628: --- import std.math; import std.stdio; void main() { immutable real x = 46; immutable float xf = x; immutable double xd = x; immutable short neg2 = -2; immutable long neg8 = -8; writefln!"%.70f"(pow(xd, neg2)); writefln!"%.70f"(cast(double) (1 / (x * x))); writefln!"%.70f"(pow(xf, neg8)); writefln!"%.70f"(cast(float) (1 / ((x * x) * (x * x) * (x * x) * (x * x))))$ assert(pow(xd, neg2) == cast(double) (1 / (x * x))); // line 7902 assert(pow(xf, neg8) == cast(float) (1 / ((x * x) * (x * x) * (x * x) * (x $ } --- I ran essentially this program in the testsuite and got: 0.0004725897920604915061933148923145608932827599346637725830078125000000 0.0004725897920604915061933148923145608932827599346637725830078125000000 0.0000000000000498812518796420273359260022516536992043256759643554687500 0.0000000000000498812518796420273359260022516536992043256759643554687500 ****** FAIL release32 std.math core.exception.AssertError std/math.d(7902): unittest failure This is the output of FreeBSD-32. On Win32 the result was essentially the same. All others worked. If this program doesn't work (I have no direct access to any of the two OSs), go to std.math, look for the test containing "neg8" and put the last 6 lines of the unittest there (and remove safe etc. from the test). Then let the testsuite run. And I'm pretty aware, that one should not compare floating point numbers with == due to rounding issues. But the output above shows, that the numbers have identical bit patterns and they are also of identical type. That should not even fail with floating point numbers. --
Dec 15 2019