[Rd] gfortran 9 quantreg bug

Balasubramanian Narasimhan n@r@@ @end|ng |rom @t@n|ord@edu
Sun Aug 4 17:20:51 CEST 2019

On 8/4/19 7:26 AM, Berend Hasselman wrote:
> Roger,
> I have run
> 	gfortran -c -fsyntax-only -fimplicit-none -Wall -pedantic rqbr.f
> in the src folder of quantreg.
> There are many warnings about defined but not used labels.
> Also two errors such as "Symbol ‘in’ at (1) has no IMPLICIT type".
> And warnings such as: Warning: "Possible change of value in conversion from REAL(8) to INTEGER(4)  at ..."
> No offense intended but this fortran code is awful. I wouldn't want to debug this before an extensive cleanup by
> getting rid of as many numerical labels as possible, indenting and doing something about the warnings "Possible change of value ...".

The unused labels at least can be removed automatically at least for 
fixed form along the lines shown in steps 8 and 9 of


which pertain to lines 261--281 of


In fact, here it is, excerpted.

code_lines  <- readLines(con = "rqbr.f")
cat("Running gfortran to detect warning lines on unused labels\n")
system2(command = "gfortran",
         args = c("-Wunused", "-c", "rqbr.f", "-o", "temp.o"),
         stderr = "gfortran.out")
cat("Scanning gfortran output for warnings on unusued labels\n")
warnings <- readLines("gfortran.out")
line_numbers <- grep('rqbr.f', warnings)
label_warning_line_numbers <- grep(pattern = "^Warning: Label [0-9]+ at", warnings)
just_warnings <- sum(grepl('Warning:', warnings))

nW <- length(label_warning_line_numbers)
for (i in seq_len(nW)) {
     offending_line <- as.integer(stringr::str_extract(warnings[line_numbers[i]], pattern = "([0-9]+)"))
     code_line <- code_lines[offending_line]
     offending_label <- stringr::str_extract(warnings[label_warning_line_numbers[i]],
                                             pattern = "([0-9]+)")
     code_lines[offending_line] <- sub(pattern = offending_label,
                                       replacement = str_pad("", width = nchar(offending_label)),
                                       x = code_lines[offending_line])
writeLines(code_lines, con = "rqbr-new.f")


> This is going to be very difficult.
> Berend Hasselman
>> On 4 Aug 2019, at 08:48, Koenker, Roger W <rkoenker using illinois.edu> wrote:
>> I’d like to solicit some advice on a debugging problem I have in the quantreg package.
>> Kurt and Brian have reported to me that on Debian machines with gfortran 9
>> library(quantreg)
>> f = summary(rq(foodexp ~ income, data = engel, tau = 1:4/5))
>> plot(f)
>> fails because summary() produces bogus estimates of the coefficient bounds.
>> This example has been around in my R package from the earliest days of R, and
>> before that in various incarnations of S.  The culprit is apparently rqbr.f which is
>> even more ancient, but must have something that gfortran 9 doesn’t approve of.
>> I note that in R-devel there have been some other issues with gfortran 9, but these seem
>> unrelated to my problem.  Not having access to a machine with an R/gfortran9
>> configuration, I can’t  apply my rudimentary debugging methods.  I’ve considered
>> trying to build gfortran on my mac air and then building R from source, but before
>> going down this road, I wondered whether others had other suggestions, or
>> advice about  my proposed route.  As far as I can see there are not yet
>> binaries for gfortran 9 for osx.
>> Thanks,
>> Roger
>> Roger Koenker
>> r.koenker using ucl.ac.uk<mailto:r.koenker using ucl.ac.uk>
>> Department of Economics, UCL
>> London  WC1H 0AX.
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