From fd66ea3543ae22d419de5e9409e9ecd06f08c1b8 Mon Sep 17 00:00:00 2001
From: kamischi <karl-michael.schindler@web.de>
Date: Thu, 29 Feb 2024 11:02:15 +0100
Subject: [PATCH] add oxlog
---
source/f90/o.f90 | 23 +++++++++++++++++++++++
tests/oxlog/o1.f90 | 2 ++
tests/oxlog/o2.f90 | 2 +-
3 files changed, 26 insertions(+), 1 deletion(-)
create mode 100644 source/f90/o.f90
diff --git a/source/f90/o.f90 b/source/f90/o.f90
new file mode 100644
index 0000000..a9f4545
--- /dev/null
+++ b/source/f90/o.f90
@@ -0,0 +1,23 @@
+double precision function o(x)
+
+! *** rational approximations for ei(x) * exp(-x) + e1(x) * exp(+x)
+! *** in the intervals (0, 1.3) and (1.3, infinity) <accuracy : 4.e-04>
+! *** used for fourier transforming half-lorentzian functions
+
+ implicit none
+
+ double precision, intent(in) :: x
+
+ if ( x < 0 ) then
+ error stop '*** Program abort. Function o is undefined for x < 0 ***'
+ elseif ( x == 0.0d0 ) then
+ o = 0.0d0
+ elseif ( x <= 1.3d0) then
+ o = -dsinh(x) * dlog(x**2) + x * ((0.03114d0 * x**2 + 0.41666d0) * x**2 + 0.84557d0)
+ else
+ o = (((202.91d0 / x**2 + 932.21d0) / x**2 + 41.740d0) / x**2 + 2.0d0) / &
+ (((540.88d0 / x**2 + 345.67d0) / x**2 + 18.961d0) / x**2 + 1.0d0) / x
+ endif
+
+ return
+end function o
diff --git a/tests/oxlog/o1.f90 b/tests/oxlog/o1.f90
index 16c9bf0..a9c9ea7 100644
--- a/tests/oxlog/o1.f90
+++ b/tests/oxlog/o1.f90
@@ -12,5 +12,7 @@ double precision function o1(u)
u2 = u**2
o1 = -dsinh(u) * dlog(u2) + u * ((0.03114d0 * u2 + 0.41666d0) * u2 + 0.84557d0)
+ write (*,*) u, o1
+
return
end function o1
diff --git a/tests/oxlog/o2.f90 b/tests/oxlog/o2.f90
index 76c562b..463402e 100644
--- a/tests/oxlog/o2.f90
+++ b/tests/oxlog/o2.f90
@@ -12,6 +12,6 @@ double precision function o2(u)
u2 = 1 / u**2
o2 = (((202.91d0 * u2 + 932.21d0) * u2 + 41.740d0) * u2 + 2.0d0) / &
(((540.88d0 * u2 + 345.67d0) * u2 + 18.961d0) * u2 + 1.0d0) / u
-
+ write (*,*) u, o2
return
end function o2
--
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