From 2125f01f97abfe343fc5e0cc078bf1d081b2e441 Mon Sep 17 00:00:00 2001
From: Ian Jauslin <ian.jauslin@roma1.infn.it>
Date: Fri, 20 May 2016 20:30:15 +0000
Subject: Initial commit

---
 doc/libinum-examples/src/root_newton.c | 58 ++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 doc/libinum-examples/src/root_newton.c

(limited to 'doc/libinum-examples/src/root_newton.c')

diff --git a/doc/libinum-examples/src/root_newton.c b/doc/libinum-examples/src/root_newton.c
new file mode 100644
index 0000000..f307c58
--- /dev/null
+++ b/doc/libinum-examples/src/root_newton.c
@@ -0,0 +1,58 @@
+#include <stdio.h>
+#include <stdarg.h>
+// define MPFR_USE_VA_LIST to enable the use of mpfr_inits and mpfr_clears
+#define MPFR_USE_VA_LIST
+#include <mpfr.h>
+#include <libinum.h>
+
+int func(mpfr_t* out, mpfr_t in, void* extra_args);
+int dfunc(mpfr_t* out, mpfr_t in, void* extra_args);
+
+int main(int argc, const char* argv[]){
+  int ret;
+  mpfr_t init, prec, x;
+  unsigned int maxiter;
+  int extra_arg;
+
+  mpfr_inits(init, prec, x, NULL);
+
+  // start at 2
+  mpfr_set_ui(init, 2, MPFR_RNDN);
+  // precision
+  mpfr_set_d(prec, 1.e-30, MPFR_RNDN);
+  // maximum number of iterations before error
+  maxiter=10000;
+  // extra argument
+  extra_arg=4;
+
+  // compute root
+  ret=root_newton_mpfr(&x, &func, &dfunc, init, prec, maxiter, &extra_arg);
+
+  // return codes
+  if(ret==LIBINUM_ERROR_MAXITER){
+    printf("error: maximum number of iterations reached\n");
+  }
+  else if(ret==LIBINUM_ERROR_NAN){
+    printf("error: infinity encountered\n");
+  }
+  else{
+    mpfr_printf("% 14.7Re\n", x);
+  }
+
+  mpfr_clears(init, prec, x, NULL);
+
+  return(0);
+}
+
+// x^2-1
+int func(mpfr_t* out, mpfr_t in, void* extra_args){
+  mpfr_pow_ui(*out, in, 2, MPFR_RNDN);
+  mpfr_add_d(*out, *out, -1./ *((int*)extra_args), MPFR_RNDN);
+  return(0);
+}
+
+// 2*x
+int dfunc(mpfr_t* out, mpfr_t in, void* extra_args){
+  mpfr_mul_ui(*out, in, 2, MPFR_RNDN);
+  return(0);
+}
-- 
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