Re: Strange performance behaviour
- From: Mike Pall <mike-1208@xxxxxxxxxx>
- To: luajit@xxxxxxxxxxxxx
- Date: Mon, 27 Aug 2012 15:48:12 +0200
Justin Cormack wrote:
> On Sat, Aug 25, 2012 at 11:51 PM, Mike Pall <mike-1208@xxxxxxxxxx> wrote:
> > I just eliminated a big on: strtod(). Yay!
> > [I can post the test cases, if anyone is interested. Almost all
> > strtod() implementations are buggy, as I found out.]
>
> Please do post the test cases.
Only, if you promise NOT to spam the list with the results! :-)
Send them to the respective library maintainers if you want.
GLIBC has already be taken care of (Florian: this one got a couple
more hairy overflow/underflow tests).
Oh, and yes, MSVCRT doesn't support any hex float conversions
(BTW: the pseudo workaround in Lua 5.2 is broken beyond repair).
It's hopeless, anyway (read the URLs, somebody tried to report it
already).
You need to use the latest LuaJIT git HEAD to pass all tests in
'tonumber' mode (testing the internal implementation I wrote).
--Mike
local ffi = require("ffi")
local bit = require("bit")
ffi.cdef[[
double strtod(const char *, char **);
]]
local t = {
-- Errors
false, "",
false, " ",
false, "+",
false, "z",
false, ".",
false, ".z",
false, "0.z",
false, ".0z",
false, "0xz",
false, "0x.z",
false, "0x0.z",
false, "0x.0z",
false, ".e5",
false, ".p4",
false, "1.p4",
false, "1.p+4",
false, "0x1.e+4",
false, "infi",
false, "nano",
false, "+ 1",
false, "- 9",
-- Spacing
0x3ff0000000000000ULL, " \t\n\v\f\r 1",
-- inf/nan
0x7ff0000000000000ULL, "iNF",
0xfff0000000000000ULL, "-Inf",
0x7ff0000000000000ULL, "+iNfInItY",
0xfff0000000000000ULL, "-INFINITY",
0xfff8000000000000ULL, "naN",
0xfff8000000000000ULL, "+NaN",
0xfff8000000000000ULL, "-nAn",
-- Smallest/largest numbers
0x0000000000000000ULL, "0e1000",
0x0000000000000000ULL, "0e-1000",
0x0000000000000000ULL, "0x0p2000",
0x0000000000000000ULL, "0x0p-2000",
0x7ff0000000000000ULL, "1e1000",
0x0000000000000000ULL, "1e-1000",
0xfff0000000000000ULL, "-1e1000",
0x7ff0000000000000ULL, "0x1p2000",
0x0000000000000000ULL, "0x1p-2000",
0xfff0000000000000ULL, "-0x1p2000",
0x0010000000000000ULL, "2.2250738585072014e-308",
0x7fefffffffffffffULL, "1.7976931348623158e+308",
0x8000b8157268fdafULL, "-1e-309",
0x000ac941b426dd3bULL, "1.5e-308",
0x000ac941b426dd3bULL, "0x0.ac941b426dd3b7p-1022",
0x0000000000000001ULL, "4.9406564584124654e-324",
0x000f9c7573d7fe52ULL, "2.171e-308",
0x241d21ecf36d4a22ULL, "1.0020284025808569e-134",
0x0000000000000001ULL, "0x1p-1074",
0x0000000000000000ULL, "0x1p-1075",
0x0000000000000000ULL, "0x1p-1076",
0x0000000000000000ULL, "0x0.ffffffffffffffffffffffffffp-1075",
0x0000000000000000ULL, "0x1.00000000000000000000000000p-1075",
0x0000000000000001ULL, "0x1.00000000000000000000000001p-1075",
0x7fe0000000000000ULL, "0x1p1023",
0x7ff0000000000000ULL, "0x1p1024",
0x7ff0000000000000ULL, "0x1p1025",
0x7ff0000000000000ULL, "0x3p1023",
0x7ff0000000000000ULL, "0x3.ffffffffffffecp1023",
0xfff0000000000000ULL, "-0xf7dcba98765432p969",
0x7fefffffffffffffULL, "0x1.fffffffffffff0000000000000p1023",
0x7fefffffffffffffULL, "0x1.fffffffffffff0000000000001p1023",
0x7fefffffffffffffULL, "0x1.fffffffffffff7ffffffffffffp1023",
0x7ff0000000000000ULL, "0x1.fffffffffffff8000000000000p1023",
0x7fefffffffffffffULL,
"179769313486231570814527423731704356798070567525844996598917476803157260780028538760589558632766878171540458953514382464234321326889464182768467546703537516986049910576551282076245490090389328944075868508455133942304583236903222948165808559332123348274797826204144723168738177180919299881250404026184124858368.0",
0x7fefffffffffffffULL,
"179769313486231580793728971405303415079934132710037826936173778980444968292764750946649017977587207096330286416692887910946555547851940402630657488671505820681908902000708383676273854845817711531764475730270069855571366959622842914819860834936475292719074168444365510704342711559699508093042880177904174497791.999",
0x7ff0000000000000ULL,
"179769313486231580793728971405303415079934132710037826936173778980444968292764750946649017977587207096330286416692887910946555547851940402630657488671505820681908902000708383676273854845817711531764475730270069855571366959622842914819860834936475292719074168444365510704342711559699508093042880177904174497792.0",
0x3ff0000000000000ULL,
"0x100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000p-1028",
-- Old GLIBC bug
0x4370000000000000ULL, "0x100000000000008p0",
--
http://www.exploringbinary.com/15-digit-quick-and-dirty-conversions-dont-round-trip/
0x04409cf3929ffbc3ULL, "3.409452297963e-288",
0x7fe02b4782a6c378ULL, "9.08344e+307",
0x6e05e258a3929ee5ULL, "9.88819e+221",
--
http://www.exploringbinary.com/incorrectly-rounded-conversions-in-gcc-and-glibc/
0x3fe0000000000002ULL,
"0.500000000000000166533453693773481063544750213623046875",
0x42c0000000000002ULL, "3.518437208883201171875e13",
0x404f44abd5aa7ca4ULL, "62.5364939768271845828",
0x3e0bd5cbaef0fd0cULL, "8.10109172351e-10",
0x3ff8000000000000ULL,
"1.50000000000000011102230246251565404236316680908203125",
0x433fffffffffffffULL, "9007199254740991.4999999999999999999999999999999995",
0x7ecd2e77eb6e3fadULL, "6.253649397682718e+302",
0x7ecd2e77eb6e3fadULL, "6.2536493976827180e+302",
--
http://www.exploringbinary.com/incorrectly-rounded-conversions-in-visual-c-plus-plus/
0x43405e6cec57761aULL, "9214843084008499",
0x3fe0000000000002ULL,
"0.500000000000000166533453693773481063544750213623046875",
0x44997a3c7271b021ULL, "30078505129381147446200",
0x4458180d5bad2e3eULL, "1777820000000000000001",
0x3fe0000000000002ULL,
"0.500000000000000166547006220929549868969843373633921146392822265625",
0x3fe0000000000002ULL,
"0.50000000000000016656055874808561867439493653364479541778564453125",
0x3fd92bb352c4623aULL, "0.3932922657273",
--
http://www.exploringbinary.com/php-hangs-on-numeric-value-2-2250738585072011e-308/
0x0010000000000000ULL, "2.2250738585072012e-308",
--
http://www.exploringbinary.com/incorrectly-rounded-subnormal-conversions-in-java/
0x0000000008000000ULL,
"6.631236871469758276785396630275967243399099947355303144249971758736286630139265439618068200788048744105960420552601852889715006376325666595539603330361800519107591783233358492337208057849499360899425128640718856616503093444922854759159988160304439909868291973931426625698663157749836252274523485312442358651207051292453083278116143932569727918709786004497872322193856150225415211997283078496319412124640111777216148110752815101775295719811974338451936095907419622417538473679495148632480391435931767981122396703443803335529756003353209830071832230689201383015598792184172909927924176339315507402234836120730914783168400715462440053817592702766213559042115986763819482654128770595766806872783349146967171293949598850675682115696218943412532098591327667236328125e-316",
0x0000000000010000ULL,
"3.237883913302901289588352412501532174863037669423108059901297049552301970670676565786835742587799557860615776559838283435514391084153169252689190564396459577394618038928365305143463955100356696665629202017331344031730044369360205258345803431471660032699580731300954848363975548690010751530018881758184174569652173110473696022749934638425380623369774736560008997404060967498028389191878963968575439222206416981462690113342524002724385941651051293552601421155333430225237291523843322331326138431477823591142408800030775170625915670728657003151953664260769822494937951845801530895238439819708403389937873241463484205608000027270531106827387907791444918534771598750162812548862768493201518991668028251730299953143924168545708663913273994694463908672332763671875e-319",
0x0000800000000100ULL,
"6.953355807847677105972805215521891690222119817145950754416205607980030131549636688806115726399441880065386399864028691275539539414652831584795668560082999889551357784961446896042113198284213107935110217162654939802416034676213829409720583759540476786936413816541621287843248433202369209916612249676005573022703244799714622116542188837770376022371172079559125853382801396219552418839469770514904192657627060319372847562301074140442660237844114174497210955449896389180395827191602886654488182452409583981389442783377001505462015745017848754574668342161759496661766020028752888783387074850773192997102997936619876226688096314989645766000479009083731736585750335262099860150896718774401964796827166283225641992040747894382698751809812609536720628966577351093292236328125e-310",
0x0000000000010800ULL,
"3.339068557571188581835713701280943911923401916998521771655656997328440314559615318168849149074662609099998113009465566426808170378434065722991659642619467706034884424989741080790766778456332168200464651593995817371782125010668346652995912233993254584461125868481633343674905074271064409763090708017856584019776878812425312008812326260363035474811532236853359905334625575404216060622858633280744301892470300555678734689978476870369853549413277156622170245846166991655321535529623870646888786637528995592800436177901746286272273374471701452991433047257863864601424252024791567368195056077320885329384322332391564645264143400798619665040608077549162173963649264049738362290606875883456826586710961041737908872035803481241600376705491726170293986797332763671875e-319",
}
local function tohex64(x)
return bit.tohex(tonumber(x/2LL^32))..bit.tohex(tonumber(x%2LL^32))
end
local conv
if arg and arg[1] == "tonumber" then
conv = tonumber
elseif arg and arg[1] == "strtod" then
local e = ffi.new("char *[1]")
function conv(s)
local d = ffi.C.strtod(s, e)
return (e[0][0] == 0 and #s ~= 0) and d or nil
end
else
io.stderr:write[[
String to number conversion tests. Specify which implementation to test:
tonumber internal implementation
strtod strtod() C library call
Note: Failures for NaN tests are expected for strtod(), since there's
no requirement to return the platform-specific canonical NaN.
]]
os.exit(1)
end
local u = ffi.new("union { double d; uint64_t x; }")
for i=1,#t,2 do
local y, s = t[i], t[i+1]
local d = conv(s)
local ok
if d == nil then
ok = (y == false)
else
u.d = d
ffi.copy(u, u, 8) -- force to memory
ok = (y == u.x)
end
if not ok then
io.write('FAIL: "', s, '"\n GOT: ', d and tohex64(u.x) or 'nil',
' OK: ', y and tohex64(y) or 'nil', '\n\n')
end
end
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