[Version 3.9.0] Infinite loop in slasq3

[Peter9606]

When input parameters to "slasq3" follows below pattern:
i0 =3, n0=16, pp=1,desig=0.2f, qmax=0.2f, nfail=4,iter=1, ndiv = 2, ieee = 0, ttype = -1
this function falls into infinite loop in-between code line 332 ~ 362.
100% reproduce.

[martin-frbg]

Do you think this used to work in earlier versions ? AFAIK none of the slasq functions was modified since at least 3.7.0. From your description it is looping as TAU never gets small enough ?

[Peter9606]

Do you think this used to work in earlier versions ? AFAIK none of the slasq functions was modified since at least 3.7.0. From your description it is looping as TAU never gets small enough ?

Sorry, I only verified on 3.9.0 so far for this is the only version at hand.

[martin-frbg]

Would you happen to have a complete reproducer for this, in particular with the values contained in the array z ? I cannot reproduce the problem with the data you provided and a random z, and I imagine bad things will happen if not even when any of the array elements is a NaN.

[mu578]

if dmin is nan it should be set to some legit erroneous value; would prevent infinity.

[martin-frbg]

I thought about this as well, but if I am correct about the rules for comparing against NaN this is probably not the problem.

[weslleyspereira]

No infinite loop using 4b3c7c2 to build the code:

      PROGRAM testSLASQ3
      IMPLICIT NONE

*     .. Scalar Arguments ..
      LOGICAL            IEEE
      INTEGER            I0, ITER, N0, NDIV, NFAIL, PP, TTYPE
      REAL               DESIG, DMIN, DMIN1, DMIN2, DN, DN1, DN2, G,
     &                   QMAX, SIGMA, TAU
*     .. Array Arguments ..
      REAL               Z( 64 )
*     .. Subroutines ..
      EXTERNAL           SLASQ3
      
      PARAMETER ( IEEE=.FALSE. )
      PARAMETER ( I0 = 3 )
      PARAMETER ( QMAX = 1.0 )

      ITER=1
      N0=16
      NDIV=2
      NFAIL=4
      PP=1
      TTYPE=-1
      DESIG=0.2
      DMIN1=0.1
      DMIN2=0.1
      DN=1.0
      DN1=1.0
      DN2=1.0
      G=1.0
      TAU=1.0

      Z = (/0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9,1.0,
     &      0.1,0.2,0.3,0.4,0.5,0.6,
     &      0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9,1.0,
     &      0.1,0.2,0.3,0.4,0.5,0.6,
     &      0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9,1.0,
     &      0.1,0.2,0.3,0.4,0.5,0.6,
     &      0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9,1.0,
     &      0.1,0.2,0.3,0.4,0.5,0.6/)
     
      CALL SLASQ3( I0, N0, Z, PP, DMIN, SIGMA, DESIG, QMAX, NFAIL,
     &                   ITER, NDIV, IEEE, TTYPE, DMIN1, DMIN2, DN, DN1,
     &                   DN2, G, TAU )

      END PROGRAM testSLASQ3

[langou]

Based on @weslleyspereira post, let us close this issue then.
@Peter9606 thanks for reporting the issue, if the issue comes back, please come back to us.
Julien.