Description
Description
Consider the following code
program main
use iso_fortran_env, only: output_unit
use stdlib_kinds, only: dp
use stdlib_linalg, only: solve_lstsq
implicit none
! Dimension of the problem.
integer, parameter :: m = 100, n = m-1
integer :: k
complex(dp) :: A(m, n), b(m), x_true(n), x_lstsq(n)
do k = 1, n
! Zero-out data.
A = 0.0_dp ; b = 0.0_dp ; x_true = 0.0_dp ; x_lstsq = 0.0_dp
! Generate a random least-squares problem of size (k+1, k).
call random_number(A(:k+1, :k)%re) ; call random_number(A(:k+1, :k)%im)
call random_number(x_true(:k)%re) ; call random_number(x_true(:k)%im)
b(:k+1) = matmul(A(:k+1, :k), x_true(:k))
! Solve the lstsq problem.
call solve_lstsq(A(:k+1, :k), b(:k+1), x_lstsq(:k))
! Check correctness of the solution.
write(output_unit, *) "Iteration k", k, norm2(abs(x_true - x_lstsq))
end do
end program mainAlthough it looks quite contrived, it is adapted from a naïve implementation of a gmres solver where A actually is upper Hessenberg. It thus corresponds to the increasingly larger least-squares problem that needs to be solved at each iteration of the gmres solver. In this MWE, A is generated as a random matrix just to make sure the error I'll report does not depends on the structure of the matrix.
Initially, everything runs just fine. However, the code crashes for k equal 39 with the following error:
Program received signal SIGSEGV: Segmentation fault - invalid memory reference.
Backtrace for this error:
#0 0x7f147f8eb51f in ???
#1 0x7f147f94b838 in ???
#2 0x7f147f94e452 in ???
#3 0x559663cefe05 in __stdlib_linalg_MOD_stdlib_linalg_z_solve_lstsq_one
at build/dependencies/stdlib/src/stdlib_linalg_least_squares.f90:1142
#4 0x559663cc6b47 in MAIN__
at app/main.f90:115
#5 0x559663ccd799 in main
at app/main.f90:3
Segmentation fault (core dumped)
<ERROR> Execution for object " MWE_stdlib_lstsq " returned exit code 139
<ERROR> *cmd_run*:stopping due to failed executions
STOP 139
Not that the error reported actually randomly switches between double free or corruption (out) (with STOP 134), SIGSEGV (with STOP 139), munmap_chunk(): invalid pointer (with STOP 134), or free(): invalide size (with STOP 134). If single precision is used instead of double precision, the code crashes at iteration k = 39 instead.
Expected Behaviour
The code should runs smoothly. Note that if real variables instead of complex ones are being used, no problem is encountered.
Version of stdlib
0.6.1
Platform and Architecture
Linux with Ubuntu 22.04
Additional Information
The code is generated with fpm and the latest stdlib version is fetched directly by fpm. The code is compiled with gfortran 13.2.0 installed with conda.