From 335c3a23f09759be380291ec89b0f2c43c2d3db6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andreas=20M=C3=BCller?= <andreas.mueller@ost.ch>
Date: Sat, 25 Jun 2022 22:46:16 +0200
Subject: fix agm

---
 buch/chapters/110-elliptisch/agm/agm.cpp | 42 ++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)
 create mode 100644 buch/chapters/110-elliptisch/agm/agm.cpp

(limited to 'buch/chapters/110-elliptisch/agm/agm.cpp')

diff --git a/buch/chapters/110-elliptisch/agm/agm.cpp b/buch/chapters/110-elliptisch/agm/agm.cpp
new file mode 100644
index 0000000..fdb0441
--- /dev/null
+++ b/buch/chapters/110-elliptisch/agm/agm.cpp
@@ -0,0 +1,42 @@
+/*
+ * agm.cpp
+ *
+ * (c) 2022 Prof Dr Andreas Müller, OST Ostschweizer Fachhochschule
+ */
+#include <cstdlib>
+#include <cstdio>
+#include <cmath>
+#include <iostream>
+#include <gsl/gsl_sf_ellint.h>
+
+
+
+int	main(int argc, char *argv[]) {
+	long double	a = 1;
+	long double	b = sqrtl(2.)/2;
+	if (argc >= 3) {
+		a = std::stod(argv[1]);
+		b = std::stod(argv[2]);
+	}
+
+	{
+		long double	an = a;
+		long double	bn = b;
+		for (int i = 0; i < 10; i++) {
+			printf("%d  %24.18Lf  %24.18Lf  %24.18Lf\n",
+				i, an, bn, a * M_PI / (2 * an));
+			long double A = (an + bn) / 2;
+			bn = sqrtl(an * bn);
+			an = A;
+		}
+	}
+
+	{
+		double	k = b/a;
+		k = sqrt(1 - k*k);
+		double	K = gsl_sf_ellint_Kcomp(k, GSL_PREC_DOUBLE);
+		printf("                             %24.18f  %24.18f\n", k, K);
+	}
+
+	return EXIT_SUCCESS;
+}
-- 
cgit v1.2.1