Fortran Sort Method Numerical recipies - sorting

Question

i m using C to Call Fortran,
my fortran is calling sort() method
*-----------------------------------------------------------------------
* SUBROUTINE sort(A,n)
* Subroutine de la librairie "Numerical Recipes"
* (C) Copr. 1986-92 Numerical Recipes Software
*-----------------------------------------------------------------------
SUBROUTINE sort(arr,n)
INTEGER n,M,NSTACK
REAL arr(n)
PARAMETER (M=7,NSTACK=50)
INTEGER i,ir,j,jstack,k,l,istack(NSTACK)
REAL a,temp
jstack=0
l=1
ir=n
1 if(ir-l.lt.M)then
do 12 j=l+1,ir
a=arr(j)
do 11 i=j-1,1,-1
if(arr(i).le.a)goto 2
arr(i+1)=arr(i)
11 continue
i=0
2 arr(i+1)=a
12 continue
if(jstack.eq.0)return
ir=istack(jstack)
l=istack(jstack-1)
jstack=jstack-2
else
k=(l+ir)/2
temp=arr(k)
arr(k)=arr(l+1)
arr(l+1)=temp
if(arr(l+1).gt.arr(ir))then
temp=arr(l+1)
arr(l+1)=arr(ir)
arr(ir)=temp
endif
if(arr(l).gt.arr(ir))then
temp=arr(l)
arr(l)=arr(ir)
arr(ir)=temp
endif
if(arr(l+1).gt.arr(l))then
temp=arr(l+1)
arr(l+1)=arr(l)
arr(l)=temp
endif
i=l+1
j=ir
a=arr(l)
3 continue
i=i+1
if(arr(i).lt.a)goto 3
4 continue
j=j-1
if(arr(j).gt.a)goto 4
if(j.lt.i)goto 5
temp=arr(i)
arr(i)=arr(j)
arr(j)=temp
goto 3
5 arr(l)=arr(j)
arr(j)=a
jstack=jstack+2
if(jstack.gt.NSTACK)pause 'NSTACK too small in sort'
if(ir-i+1.ge.j-l)then
istack(jstack)=ir
istack(jstack-1)=i
ir=j-1
else
istack(jstack)=j-1
istack(jstack-1)=l
l=i
endif
endif
goto 1
END
And if i call sort method many times, i have a segfault in this method :(
It's legacy code but i'm trust in it because it come from numerical recipies.
But i'm suspicious about some things, in particular this line :
if(jstack.gt.NSTACK)pause 'NSTACK too small in sort'
If i'm in this case, my programm will in pause? how it's possible that a sort method do this?
And if this line is suspicious, how can i trust the entire code?
does anyone know a problem with this sort subroutine? does anybody know another method to doing sort in fortran? Because i can replace this sort method by another one but i'm new in fortran and i can't write another one.
I add that no problem if i run this method in mono thread, but if i run it in multi thread environement, problem is here. sorry to don't mentionned when i wrote my question but i see this after writing it.
DEBUG information
current thread: t#41
[1] __lwp_kill(0x0, 0x6, 0x0, 0x6, 0xffbffeff, 0x0), at 0xff2caa58
[2] raise(0x6, 0x0, 0xff342f18, 0xff2aa378, 0xffffffff, 0x6), at 0xff265a5c
[3] abort(0x7400, 0x1, 0x0, 0xfcb78, 0xff3413d8, 0x0), at 0xff24194c
[4] os::abort(0x1, 0x0, 0xff011084, 0xfefdc000, 0x7d94, 0x7c00), at 0xfee7d3cc
[5] VMError::report_and_die(0x0, 0xff038640, 0xff031ff4, 0x1, 0xfee81b94, 0xff031ff4), at 0xfef0cd58
[6] JVM_handle_solaris_signal(0xb, 0xacffefe0, 0xacffed28, 0x8000, 0xff030fa0, 0x2013d8), at 0xfea73d48
[7] __sighndlr(0xb, 0xacffefe0, 0xacffed28, 0xfea7325c, 0x0, 0x1), at 0xff2c6e78
---- called from signal handler with signal 11 (SIGSEGV) ------
[8] sort_(0xfe2b1350, 0xfe2b135c, 0xfe2b1000, 0x1c00, 0x443bfc7b, 0xfe292484), at 0xfe27e498
[9] mediane_(0xa9c1624c, 0xacfff2ac, 0xa9c16060, 0xa9c05c34, 0x0, 0x19), at 0xfe27a38c
(dbx) frame 8
0xfe27e498: sort_+0x01d8: ld [%l4 + %l1], %f4
(dbx) disassemble
0xff2caa58: __lwp_kill+0x0008: bcc,a,pt %icc,__lwp_kill+0x18 ! 0xff2caa68
0xff2caa5c: __lwp_kill+0x000c: clr %o0
0xff2caa60: __lwp_kill+0x0010: cmp %o0, 91
0xff2caa64: __lwp_kill+0x0014: move %icc,0x4, %o0
0xff2caa68: __lwp_kill+0x0018: retl
0xff2caa6c: __lwp_kill+0x001c: nop
0xff2caa70: __lwp_self : mov 164, %g1
0xff2caa74: __lwp_self+0x0004: ta %icc,0x00000008
0xff2caa78: __lwp_self+0x0008: retl
0xff2caa7c: __lwp_self+0x000c: nop
in m in solaris with dbx=> gdb on
i try to inspect adress but what can i type to have interesting informations?
After adding -g option to f90 compiler, in dbx i can see value or var and see the result:
t#88 (l#88) terminated by signal ABRT (Abort)
0xff2caa58: __lwp_kill+0x0008: bcc,a,pt %icc,__lwp_kill+0x18 ! 0xff2caa68
Current function is sort
578 temp=arr(k)
(dbx) print n
n = 19
(dbx) print arr
arr =
(1) 725.0666
(2) 741.5034
(3) 730.8196
(4) 754.3707
(5) 741.718
(6) 741.718
(7) 741.8914
(8) 745.9141
(9) 744.6705
(10) 741.718
(11) 745.8358
(12) 743.3788
(13) 746.2706
(14) 746.2706
(15) 750.1498
(16) 754.3707
(17) 754.3707
(18) 754.3707
(19) 748.2084
(dbx) print istack
istack =
(1) 7
(2) 12
(3) 17
(4) 18
(5) 8
(6) 9
(7) 1
(8) 4
(9) 0
(10) 0
(11) 0
(12) 0
(13) 0
(14) 0
(15) 0
(16) 0
(17) 0
(18) 0
(19) 0
(20) 0
(21) 0
(22) 0
(23) 0
(24) 0
(25) 0
(26) 0
(27) 0
(28) 0
(29) 0
(30) 0
(31) 0
(32) 0
(33) 0
(34) 0
(35) 0
(36) 0
(37) 0
(38) 0
(39) 0
(40) 0
(41) 0
(42) 0
(43) 0
(44) 0
(45) 0
(46) 0
(47) 0
(48) 0
(49) 0
(50) 0
(dbx) print jstack
jstack = -31648
(dbx)
how its possible taht jstack have a -31648 val! istack have only 50 element and istack(jstack) retrun me a abd value! how its possible? :)
thanks by advance

Answer 1

Too large for a comment:
Unfortunately the stack trace does not show the exact line of failure. What is the evidence that the error is at the line you indicated. I could imagine there could be error in calling the run-time system, sou you should try to change the PAUSE statement to write, read *, or something similar.
I did some tests with your subroutine in gfortran:
parameter (n = 100000)
dimension b(n)
do i=1,1000
call random_number(b)
call sort(b,n)
end do
end
with different array sizes and loop bounds. This calls the sort with many different inputs. I enabled all checks and sanitizations and didn't encounter a single problem.
Edit:
It works with OpenMP too:
parameter (n = 100000)
real,allocatable :: b(:)
!$omp parallel private(b)
allocate(b(n))
!$omp do
do i=1,1000
call random_number(b)
call sort(b,n)
end do
!$omp end do
!$omp end parallel
end