http://d.puremagic.com/issues/show_bug.cgi?id=9584
Summary: Exceptions in D are ludicrously slow (far worse than Java) Product: D Version: D2 Platform: All OS/Version: All Status: NEW Severity: normal Priority: P2 Component: druntime AssignedTo: nob...@puremagic.com ReportedBy: jmdavisp...@gmx.com --- Comment #0 from Jonathan M Davis <jmdavisp...@gmx.com> 2013-02-24 15:46:57 PST --- Take this D program ------ import std.conv; import std.datetime; import std.stdio; void main() { auto sw = StopWatch(AutoStart.yes); try throw new Exception("blah"); catch(Exception e) { auto diff = to!Duration(sw.peek()); writeln(diff.total!"hnsecs"()); writeln(diff); } } ------ and this Java program ------ class j { public static final void main(String[] args) { long before = System.nanoTime(); try { throw new Exception("blah"); } catch(Exception e) { long diff = System.nanoTime() - before; long totalHNSecs = diff / 100; long msecs = diff / 1000000; diff -= msecs * 1000000; long usecs = diff / 1000; diff -= usecs * 1000; long hnsecs = diff / 100; System.out.println(totalHNSecs); System.out.printf("%sms %sus %shnsecs\n", msecs, usecs, hnsecs); } } } ------ They are roughly equivalent, but their performance is drastically different (and Java wins by a _long_ shot). These are typical outputs for the D version 13962 1 ms, 396 μs, and 2 hnsecs 13658 1 ms, 365 μs, and 8 hnsecs 13745 1 ms, 374 μs, and 5 hnsecs whereas tese are typical outputs for the Java version 126 0ms 12us 6hnsecs 126 0ms 12us 6hnsecs 140 0ms 14us 0hnsecs It varies a bit from execution to execution (particularly for D), but in general, I'm seeing that D is taking 90x - 110x longer than Java is. Oddly, once in a blue moon, D seems to take more like 20x longer, but even that's a huge difference (and not in D's favor). In general, Java shouldn't be beating D for performance, since D is a systems language, and a magnitute of 100x is pathetic. Granted, code should not be constantly throwing and catching exeptions, but this sort of bad performance can make it so that exceptions have far more of a negative impact then they should. The place that this is particularly negative is in unit tests. Good unit tests will test that functions act appropriately when given bad input, which generally means that they throw exceptions, and the tests catch them, and right now, if you do much of that, unit tests start taking a very long time to execute - unacceptably long. This makes it so that code must be tested less in order for the tests to take a reasonable amount of time, which will lead to worse code quality. So, I think that it's clear that we need to take steps to improve the performance of throwing and catching exceptions. As I understand it, the stacktrace is currently put into string format when the exception is constructed, which is unnecessary overhead if the stack trace never gets printed, so that's one improvement that could be made. But I have no idea how the internals of any of this currently work, so I don't know what other improvements could be made. Regardless, we need to take steps to significantly improve the situation. Note that these tests were done on Linux. I don't know how the times compare on Windows, though I expect that the situation is similar there. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------