Intel Fortran Compiler Mac OS X optimization bug

[oacikgoz]

The following code gives me inconsistent results. It runs fine with optimization turned off.

The screen output with optimization is (sometimes quits with SIGSEGV)

2.122514567798456E-314 2.122514567798456E-314

0.826680222897825 2.122514567798456E-314

Without optimization, I get the right numbers

-0.999305041735772 1.783280721696433E-003

3.474791321139148E-004 1.783280721696433E-003

Here is the code

PROGRAM main

IMPLICIT NONE

INTEGER :: i

REAL(8), DIMENSION(:), ALLOCATABLE :: xt

REAL(8), DIMENSION(:), ALLOCATABLE :: wt

ALLOCATE(xt(64))

ALLOCATE(wt(64))

xt(1) = - 0.999305041735772139456905624346D+00

xt(2) = - 0.996340116771955279346924500676D+00

xt(3) = - 0.991013371476744320739382383443D+00

xt(4) = - 0.983336253884625956931299302157D+00

xt(5) = - 0.973326827789910963741853507352D+00

xt(6) = - 0.961008799652053718918614121897D+00

xt(7) = - 0.946411374858402816062481491347D+00

xt(8) = - 0.929569172131939575821490154559D+00

xt(9) = - 0.910522137078502805756380668008D+00

xt(10) = - 0.889315445995114105853404038273D+00

xt(11) = - 0.865999398154092819760783385070D+00

xt(12) = - 0.840629296252580362751691544696D+00

xt(13) = - 0.813265315122797559741923338086D+00

xt(14) = - 0.783972358943341407610220525214D+00

xt(15) = - 0.752819907260531896611863774886D+00

xt(16) = - 0.719881850171610826848940217832D+00

xt(17) = - 0.685236313054233242563558371031D+00

xt(18) = - 0.648965471254657339857761231993D+00

xt(19) = - 0.611155355172393250248852971019D+00

xt(20) = - 0.571895646202634034283878116659D+00

xt(21) = - 0.531279464019894545658013903544D+00

xt(22) = - 0.489403145707052957478526307022D+00

xt(23) = - 0.446366017253464087984947714759D+00

xt(24) = - 0.402270157963991603695766771260D+00

xt(25) = - 0.357220158337668115950442615046D+00

xt(26) = - 0.311322871990210956157512698560D+00

xt(27) = - 0.264687162208767416373964172510D+00

xt(28) = - 0.217423643740007084149648748989D+00

xt(29) = - 0.169644420423992818037313629748D+00

xt(30) = - 0.121462819296120554470376463492D+00

xt(31) = - 0.729931217877990394495429419403D-01

xt(32) = - 0.243502926634244325089558428537D-01

xt(33) = 0.243502926634244325089558428537D-01

xt(34) = 0.729931217877990394495429419403D-01

xt(35) = 0.121462819296120554470376463492D+00

xt(36) = 0.169644420423992818037313629748D+00

xt(37) = 0.217423643740007084149648748989D+00

xt(38) = 0.264687162208767416373964172510D+00

xt(39) = 0.311322871990210956157512698560D+00

xt(40) = 0.357220158337668115950442615046D+00

xt(41) = 0.402270157963991603695766771260D+00

xt(42) = 0.446366017253464087984947714759D+00

xt(43) = 0.489403145707052957478526307022D+00

xt(44) = 0.531279464019894545658013903544D+00

xt(45) = 0.571895646202634034283878116659D+00

xt(46) = 0.611155355172393250248852971019D+00

xt(47) = 0.648965471254657339857761231993D+00

xt(48) = 0.685236313054233242563558371031D+00

xt(49) = 0.719881850171610826848940217832D+00

xt(50) = 0.752819907260531896611863774886D+00

xt(51) = 0.783972358943341407610220525214D+00

xt(52) = 0.813265315122797559741923338086D+00

xt(53) = 0.840629296252580362751691544696D+00

xt(54) = 0.865999398154092819760783385070D+00

xt(55) = 0.889315445995114105853404038273D+00

xt(56) = 0.910522137078502805756380668008D+00

xt(57) = 0.929569172131939575821490154559D+00

xt(58) = 0.946411374858402816062481491347D+00

xt(59) = 0.961008799652053718918614121897D+00

xt(60) = 0.973326827789910963741853507352D+00

xt(61) = 0.983336253884625956931299302157D+00

xt(62) = 0.991013371476744320739382383443D+00

xt(63) = 0.996340116771955279346924500676D+00

xt(64) = 0.999305041735772139456905624346D+00

wt(1) = 0.178328072169643294729607914497D-02

wt(2) = 0.414703326056246763528753572855D-02

wt(3) = 0.650445796897836285611736039998D-02

wt(4) = 0.884675982636394772303091465973D-02

wt(5) = 0.111681394601311288185904930192D-01

wt(6) = 0.134630478967186425980607666860D-01

wt(7) = 0.157260304760247193219659952975D-01

wt(8) = 0.179517157756973430850453020011D-01

wt(9) = 0.201348231535302093723403167285D-01

wt(10) = 0.222701738083832541592983303842D-01

wt(11) = 0.243527025687108733381775504091D-01

wt(12) = 0.263774697150546586716917926252D-01

wt(13) = 0.283396726142594832275113052002D-01

wt(14) = 0.302346570724024788679740598195D-01

wt(15) = 0.320579283548515535854675043479D-01

wt(16) = 0.338051618371416093915654821107D-01

wt(17) = 0.354722132568823838106931467152D-01

wt(18) = 0.370551285402400460404151018096D-01

wt(19) = 0.385501531786156291289624969468D-01

wt(20) = 0.399537411327203413866569261283D-01

wt(21) = 0.412625632426235286101562974736D-01

wt(22) = 0.424735151236535890073397679088D-01

wt(23) = 0.435837245293234533768278609737D-01

wt(24) = 0.445905581637565630601347100309D-01

wt(25) = 0.454916279274181444797709969713D-01

wt(26) = 0.462847965813144172959532492323D-01

wt(27) = 0.469681828162100173253262857546D-01

wt(28) = 0.475401657148303086622822069442D-01

wt(29) = 0.479993885964583077281261798713D-01

wt(30) = 0.483447622348029571697695271580D-01

wt(31) = 0.485754674415034269347990667840D-01

wt(32) = 0.486909570091397203833653907347D-01

wt(33) = 0.486909570091397203833653907347D-01

wt(34) = 0.485754674415034269347990667840D-01

wt(35) = 0.483447622348029571697695271580D-01

wt(36) = 0.479993885964583077281261798713D-01

wt(37) = 0.475401657148303086622822069442D-01

wt(38) = 0.469681828162100173253262857546D-01

wt(39) = 0.462847965813144172959532492323D-01

wt(40) = 0.454916279274181444797709969713D-01

wt(41) = 0.445905581637565630601347100309D-01

wt(42) = 0.435837245293234533768278609737D-01

wt(43) = 0.424735151236535890073397679088D-01

wt(44) = 0.412625632426235286101562974736D-01

wt(45) = 0.399537411327203413866569261283D-01

wt(46) = 0.385501531786156291289624969468D-01

wt(47) = 0.370551285402400460404151018096D-01

wt(48) = 0.354722132568823838106931467152D-01

wt(49) = 0.338051618371416093915654821107D-01

wt(50) = 0.320579283548515535854675043479D-01

wt(51) = 0.302346570724024788679740598195D-01

wt(52) = 0.283396726142594832275113052002D-01

wt(53) = 0.263774697150546586716917926252D-01

wt(54) = 0.243527025687108733381775504091D-01

wt(55) = 0.222701738083832541592983303842D-01

wt(56) = 0.201348231535302093723403167285D-01

wt(57) = 0.179517157756973430850453020011D-01

wt(58) = 0.157260304760247193219659952975D-01

wt(59) = 0.134630478967186425980607666860D-01

wt(60) = 0.111681394601311288185904930192D-01

wt(61) = 0.884675982636394772303091465973D-02

wt(62) = 0.650445796897836285611736039998D-02

wt(63) = 0.414703326056246763528753572855D-02

wt(64) = 0.178328072169643294729607914497D-02

WRITE(*,*) xt(1),wt(1)

xt=(xt+1.0D0)*0.5D0

WRITE(*,*) xt(1),wt(1)

END PROGRAM main

[oacikgoz]

Could someone please confirm this bug?

If you decide to do so, compile the above code once with flag -O0 and once with no flags. Default optimization screws it up.

I'm curious if the linux compiler has the same problem.

Thanks.

[david_car]

Works fine on Linux.

david@server:/tmp$ ifort --version

ifort (IFORT) 11.1 20100806

Copyright (C) 1985-2010 Intel Corporation. All rights reserved.

david@server:/tmp$ ifort --versionifort (IFORT) 11.1 20100806Copyright (C) 1985-2010 Intel Corporation. All rights reserved.

[oacikgoz]

Very interesting, maybe it's a bug that is fixed. I noticed I have a different version of ifort

ifort (IFORT) 11.1 20090827

I will download the newer version and give it a shot.

Thanks!

[Kevin_D_Intel · Accepted solution]

At optimization, the program fails with 11.1.067 related to the known incompatibility with linker in Xcode 3.2.2 and later. See this sticky post more details about the known linker incompatibility.

Your program runs correctly at optimization when using the advertised work around (see below): -use-asm

Your program also produces correct results without this work around when using the latest 11.1.089 update (see below) which contains a patch for this known linker incompatibility.

Using use-asm work around with 11.1.067:

$ ifort -V u78427.f90 -use-asm
Intel Fortran Intel 64 Compiler Professional for applications running on Intel 64, Version 11.1 Build 20090827 Package ID: m_cprof_p_11.1.067

Copyright (C) 1985-2009 Intel Corporation. All rights reserved.

Intel Fortran 11.1-2582

@(#)PROGRAM:ld PROJECT:ld64-97.2
Library search paths:

$ ./a.out

-0.999305041735772 1.783280721696433E-003
3.474791321139148E-004 1.783280721696433E-003


No work around needed with 11.1.089:

$ ifort -V u78427.f90

Intel Fortran Intel 64 Compiler Professional for applications running on Intel 64, Version 11.1 Build 20100806 Package ID: m_cprof_p_11.1.089
Copyright (C) 1985-2010 Intel Corporation. All rights reserved.

Intel Fortran 11.1-2755

@(#)PROGRAM:ld PROJECT:ld64-97.2
Library search paths:

$ ./a.out
-0.999305041735772 1.783280721696433E-003
3.474791321139148E-004 1.783280721696433E-003

[oacikgoz]

Thank you very much for your input! I spent so much time trying to fix my code. It ended up being a bug in the compiler+xcode. Now it all makes sense.