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Fix erroneous gaussian quadrature points in gauss_legendre #660

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Merged
merged 2 commits into from
Jun 13, 2022
Merged

Fix erroneous gaussian quadrature points in gauss_legendre #660

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c888876
fix github issue 619
hsnyder May 23, 2022
1bf4e33
add github issue link to test doc string
hsnyder May 24, 2022
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2 changes: 0 additions & 2 deletions src/stdlib_quadrature_gauss.f90
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Expand Up @@ -56,8 +56,6 @@ pure module subroutine gauss_legendre_fp64 (x, w, interval)
if (present(interval)) then
associate ( a => interval(1) , b => interval(2) )
x = 0.5_dp*(b-a)*x+0.5_dp*(b+a)
x(1) = interval(1)
x(size(x)) = interval(2)
w = 0.5_dp*(b-a)*w
end associate
end if
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22 changes: 21 additions & 1 deletion src/tests/quadrature/test_gauss.f90
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Expand Up @@ -21,7 +21,8 @@ subroutine collect_gauss(testsuite)
new_unittest("gauss-lobatto-analytic", test_gauss_lobatto_analytic), &
new_unittest("gauss-lobatto-5", test_gauss_lobatto_5), &
new_unittest("gauss-lobatto-32", test_gauss_lobatto_32), &
new_unittest("gauss-lobatto-64", test_gauss_lobatto_64) &
new_unittest("gauss-lobatto-64", test_gauss_lobatto_64), &
new_unittest("gauss-github-issue-619", test_fix_github_issue619) &
]
end subroutine

Expand All @@ -48,6 +49,25 @@ subroutine test_gauss_analytic(error)

end subroutine

subroutine test_fix_github_issue619(error)
!> See github issue https://github.com/fortran-lang/stdlib/issues/619
type(error_type), allocatable, intent(out) :: error
integer :: i

! test the values of nodes and weights
i = 5
block
real(dp), dimension(i) :: x1,w1,x2,w2
call gauss_legendre(x1,w1)
call gauss_legendre(x2,w2,interval=[-1._dp, 1._dp])

call check(error, all(abs(x1-x2) < 2*epsilon(x1(1))))
if (allocated(error)) return
call check(error, all(abs(w1-w2) < 2*epsilon(w1(1))))
end block

end subroutine

subroutine test_gauss_5(error)
!> Error handling
type(error_type), allocatable, intent(out) :: error
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