Known Issues for the NAG Library FL Interface

This document reflects all reported and resolved issues that affect recent releases of the NAG Library FL Interface.

Some of these issues may have been fixed at intermediate "point" releases of the Library, while other fixes are scheduled for incorporation at future releases. For library Marks where those fixes are not yet incorporated, a workaround for the known issue is provided wherever possible.

To find the Mark and point release number of your library, call NAG routine a00aaf( ).

For issues that affect releases of other interfaces, please also see

Order the issues by

c02agf

Synopsis	Overflow may occur if the routine attempts to scale the polynomial coefficients.
Description	In rare circumstances overflow may be observed if $scal = .TRUE.$ .
Severity	Non-critical
Issue Since Mark	16
Workaround	Set argument $scal = .FALSE.$ .

d02ngf

Synopsis	d02ngf can fail on stationary problems.
Description	d02ngf can fail on stationary problems..
Severity	Critical
Issue Since Mark	23
Fixed at Mark	27.3

d06acf

Synopsis	d06acf returns $ifail = 2$ error for some boundary meshes due to an internal scaling issue.
Description	d06acf returns $ifail = 2$ error for some boundary meshes due to an internal scaling issue.
Severity	Non-critical
Issue Since Mark	20
Fixed at Mark	28.4
Workaround	Scale input boundary mesh prior to calling d06acf so that $= 0$ and $= 1$ .

e01shf

Synopsis	e01shf will occasionally incorrectly identify a point as being outside the region defined by the interpolant.
Description	e01shf will occasionally incorrectly identify a point as being outside the region defined by the interpolant. This leads to the function value being extrapolated rather than interpolated and can lead to incorrect results.
Severity	Non-critical
Issue Since Mark	26.0
Fixed at Mark	27.1
Workaround	None.

e04dga, e04mfa, e04nca, e04nfa, e04nka, e04uca, e04ufa, e04uga and e04usa

Synopsis	No check that a mandatory call to the initialization routine has been made.
Description	Whilst it is necessary to call initialization routine e04wbf prior to calling the named e04 routines, no software check is made to ensure that this has happened.
Severity	Non-critical
Issue Since Mark	20
Workaround	Ensure that initialization routine e04wbf has been called.

e04ggf

Synopsis	In some cases, the solver hangs indefinitely at an iteration.
Description	In some cases, when certain variable lower bounds are not present, the solver might hang indefinitely due to an infinite loop during the line search stage.
Severity	Critical
Issue Since Mark	27.1
Fixed at Mark	30.3
Workaround	None.

e04mtf

Synopsis	$stats$ and $rinfo$ were not correctly filled by the presolver.
Description	The arrays $stats$ and $rinfo$ were not correctly filled when the problem was entirely solved by the presolver. It now returns the correct values. The optional parameter $Print Solution$ now correctly writes the linear constraints dual variables when no bounds are defined on the variables.
Severity	Non-critical
Issue Since Mark	26.1
Fixed at Mark	27
Workaround	Don't rely on $rinfo (1), rinfo (2)$ to hold the primal and dual objective in this case and recompute it as $c^{'} x$ and $b y$ , respectively.

e04mtf

Synopsis	e04mtf does not report the correct solution when $3$ or more columns are proportional to each other in the constraint matrix.
Description	e04mtf does not report the correct solution when $3$ or more columns are proportional to each other in the constraint matrix. In such a case, the solution reported may be infeasible.
Severity	Non-critical
Issue Since Mark	26.1
Fixed at Mark	27
Workaround	A workaround is to disable the more complex presolve operations by setting the optional parameter $LP Presolve = BASIC$ . This may slow down the solver depending on the problem.

e04mtf

Synopsis	In some very rare cases, the solution reported presents big violations on a small number of linear constraints.
Description	In some very rare cases, the solution reported presents big violations on a small number of linear constraints.
Severity	Non-critical
Issue Since Mark	26.1
Fixed at Mark	27.1
Workaround	A workaround is to deactivate the more complex presolver operations with the optional parameter $LP Presolve = BASIC$ .

e04mtf

Synopsis	In some very rare cases, e04mtf reports problem infeasibility for a feasible problem.
Description	In some very rare cases, the solver reports problem infeasibility when there are numerical difficulties.
Severity	Non-critical
Issue Since Mark	26.1
Fixed at Mark	28.6
Workaround	Unfortunately there is no convenient workaround.

e04mtf

Synopsis	In some very rare cases, at presolve phase the solver declares unboundedness on a bounded problem.
Description	In some very rare cases, especially when there are a large amount of singleton variables, the solver might report unbounded error message on a bounded problem.
Severity	Non-critical
Issue Since Mark	26.1
Fixed at Mark	29.0
Workaround	A workaround is to deactivate the more complex presolver operations with the optional parameter $LP Presolve = BASIC$ . This may slow down the solver depending on the problem.

e04mtf

Synopsis	In some cases the solver declares dual infeasibility during presolving for feasible and bounded problems.
Description	For a bounded problem, the solver reports dual infeasibility during dominated columns removal at the presolving stage.
Severity	Non-critical
Issue Since Mark	26.1
Fixed at Mark	29.1
Workaround	A workaround is to deactivate the more complex presolver operations with the optional parameter $LP Presolve = BASIC$ . This may slow down the solver depending on the problem.

e04mtf and e04ptf

Synopsis	Infeasible bounds defined by e04rjf of a variable are ignored and infeasibility is not reported.
Description	When infeasible bounds are defined by e04rjf for a variable, instead of reporting problem infeasibility, the bounds are overridden and wrong solution may be reported.
Severity	Non-critical
Issue Since Mark	26.1
Fixed at Mark	27.1
Workaround	A workaround is to deactivate the more complex presolver operations with the optional parameter $LP Presolve = BASIC$ for e04mtf and $SOCP Presolve = BASIC$ for e04ptf.

e04nrf, e04vkf and e04wef

Synopsis	Optional parameters $List$ and $Nolist$ are not handled correctly.
Description	Routines e04nrf, e04vkf and e04wef do not handle optional parameters $List$ and $Nolist$ correctly. Specifying $List$ does not alter the behaviour of subsequent routines in the suite, and specifying $Nolist$ erroneously reports an error.
Severity	Non-critical
Issue Since Mark	8
Fixed at Mark	27.3
Workaround	Routine e04nsf should be used instead to set optional parameters $List$ or $Nolist$ .

e04vhf

Synopsis	Information about the last constraint might not be printed.
Description	If the problem has a nonlinear objective function without a linear part and $objrow < nf$ , the last constraint is not printed in the final information about the solution (Rows section).
Severity	Non-critical
Issue Since Mark	21
Fixed at Mark	26
Workaround	None.

e05kbf

Synopsis	When $ifail = 4$ is returned, the expected value of $nvar$ in the error message may be wrongly reported.
Description	When $ifail = 4$ is returned, the expected value of $nvar$ in the error message may be wrongly reported. This incorrect behaviour may occur when the internal solver works with a different number of variables than what is declared during handle initialization, e.g., when some variables are fixed by the user.
Severity	Non-critical
Issue Since Mark	28.3
Fixed at Mark	30.2
Workaround	None.

f11bef, f11bsf, f11gef and f11gsf

Synopsis	Multithreaded versions of the routines f11bef, f11bsf, f11gef and f11gsf may produce slightly different results when run on multiple threads.
Description	Multithreaded versions of the routines f11bef, f11bsf, f11gef and f11gsf may produce slightly different results when run on multiple threads, e.g., the number of iterations to solution and the computed matrix norms and termination criteria reported by the associated monitoring routines. A bug affecting f11bef and f11gef has been fixed, and parallel vector dot products have been modified in all routines to improve consistency of results.
Severity	Non-critical
Issue Since Mark	19
Fixed at Mark	27.1
Workaround	None.

f16rbf and f16ubf

Synopsis	f16rbf and f16ubf return $0$ if $kl$ or $ku$ is $0$ , instead of the correct norm. $ldab$ is incorrectly forced to be at least $m$ when $m = n$ .
Description	f16rbf and f16ubf mistakenly make a quick return if $kl$ or $ku$ is $0$ , instead of computing the correct value for the requested norm. Also, $ldab$ is incorrectly forced to be at least $m$ when $m = n$ .
Severity	Critical
Issue Since Mark	23
Fixed at Mark	27.3
Workaround	None.

g02ajf

Synopsis	If the first row or column of the weight matrix $h$ consists only of zeros, then the routine will fail to find the nearest correlation matrix for that weight matrix.
Description	An error can occur when the first row or column of the weight matrix $h$ consists only of zeros, then the routine will fail to find the nearest correlation matrix for that weight matrix.
Severity	Critical
Issue Since Mark	25
Fixed at Mark	30.1
Workaround	The workaround is to apply a small weight (relative to other non-zero weights given in $h$ ) to one of the elements in the first row/column.

g02jff

Synopsis	A segmentation fault is likely to occur if a model with multiple random statements is supplied to the routine, where at least one of those statements does not have a $Subject$ term.
Description	A segmentation fault is likely to occur if a model with multiple random statements is supplied to the routine, where at least one of those statements does not have a $Subject$ term. For example, a model specified using: V1 + V2 / SUBJECT = V3 V4 + V5 / SUBJECT = V6 would not trigger the error, but one specified using: V1 + V2 V4 + V5 / SUBJECT = V6 would. The error is not triggered when there is only a single random statement, so a model specified using just V1 + V2 will not trigger the error.
Severity	Critical
Issue Since Mark	27
Fixed at Mark	27.1
Workaround	A workaround to this issue is to always supply a $Subject$ term. If the required model is of the form: V1 + V2 V4 + V5 / SUBJECT = V6 then you can specify an equivalent model by using: V1 + V2 / SUBJECT = DUMMY V4 + V5 / SUBJECT = V6 where the variable DUMMY has a single level, and always takes a value of one. This will require adding the variable DUMMY to your dataset.

g08ckf and g08clf

Synopsis	The wrong value for $p$ is returned when $aa2$ is large.
Description	In g08ckf and g08clf the value returned for the upper tail probability $p$ is wrong when the calculated Anderson-Darling test statistic $aa2$ is large. In the case of g08ckf, when $aa2 > 153.4677$ the returned value of $p$ should be zero; in the case of g08clf, when $aa2 > 10.03$ the returned value of $p$ should be $\leq \exp (- 14.360135)$ .
Severity	Critical
Issue Since Mark	23
Workaround	Workaround for g08ckf: Call g08ckf(...) If (aa2 > 153.4677d0) p = 0.0d0 Workaround for g08clf: Call g08clf(...) If (aa2 > 10.03d0) p = exp(-14.360135d0)

g13faf

Synopsis	g13faf may return a negative value as the estimate of the last $β$ parameter (i.e., $β_{p}$ ) for a subset of models.
Description	g13faf can result in a negative value for the estimate of the last $β$ parameter (i.e., $β_{p}$ ) or, if $p = 0$ , the last $α$ parameter (i.e., $α_{q}$ ). This issue only affects a subset of models that have normally distributed errors and do not include an asymmetry term. If the routine did not return a negative value as the estimate of the last $β$ parameter (or, if $p = 0$ , the last $α$ parameter), then that particular model was not affected by the issue.
Severity	Critical
Issue Since Mark	20
Fixed at Mark	27
Workaround	None

g22ydf

Synopsis	When $what ='V'$ the information returned in $plab$ and/or $vinfo$ may be incorrect.
Description	The information returned in $plab$ and/or $vinfo$ may be incorrect in cases where $what ='V'$ and the underlying linear mixed effects regression model has a random variable, with a single level (so either binary or continuous), that only takes the value zero.
Severity	Non-critical
Issue Since Mark	27.0
Workaround	The work around is to drop the term from the model, as it does not contribute. For example, if the random part of your model was specified as: V1 + V2 / SUBJECT=V3 and the variable V2 was a continuous variable, that only takes a value of zero in the data, then this is equivalent to re-specifying the model using: V1 / SUBJECT=V3.

h02daf

Synopsis	In some cases, solver returns inaccurate solution when there are binary variables.
Description	When there are binary variables, the accuracy of the solution will be influenced by the initial values. The solver could return inaccurate solution.
Severity	Non-critical
Issue Since Mark	25
Fixed at Mark	29.1
Workaround	The work around is to use integer variables with $0$ and $1$ as lower and upper bound, respectively.

Metis external package files use large amount of thread local storage (TLS)

Synopsis	Thread Local Storage default limit was exceeded for delay loaded shared library.
Description	A fair amount of thread local storage had been allocated by an auxiliary routine which has now been updated to use a very small amount of thread local storage. Prior to the update, this only affected the case where the shared version of the Nag Library was delay loaded, since this assumed a small default maximum amount of thread local storage, which was in fact exceeded. The issue had been present since the introduction of the auxiliary routine at Mark 26.1. From Mark 28.6, the amount of thread local storage used is very small and this is no longer an issue.
Severity	Non-critical
Issue Since Mark	26.1
Fixed at Mark	28.6
Workaround	None.

Static Library Linking (applies to NLL6I products only)

Synopsis	On Linux, static linking of the nAG Library using a recent Intel Fortran compiler results in a link error due to multiple defines.
Description	(This error report applies to Linux library NLL6I only). On Linux, static linking of the nAG Library using a recent Intel Fortran compiler results in a link error due to multiple defines. This is due to the inclusion of some Intel compiler runtime libraries into the static nAG Library. This was originally to simplify the linking of the nAG Library using ifort, where otherwise each such runtime would have had to be specified on the link line. However, recent versions of ifort and ifx have now added these compiler runtime libraries into the list of libraries to be linked by default. Thus, using these newer versions of ifort/ifx results in the said runtimes being linked twice.
Severity	Critical
Issue Since Mark
Fixed at Mark
Workaround	The recommended workaround is to link to the shared Library when this problem presents itself.