ajout hypot

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@1266 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 131 insertions, 0 deletions

diff --git a/hypot.c b/hypot.c
new file mode 100644
index 000000000..e68a657ae
--- /dev/null
+++ b/hypot.c
@@ -0,0 +1,131 @@
+/* mpfr_hypot -- Euclidean distance
+
+Copyright (C) 1999 Free Software Foundation.
+
+This file is part of the MPFR Library.
+
+The MPFR Library is free software; you can redistribute it and/or modify
+it under the terms of the GNU Library General Public License as published by
+the Free Software Foundation; either version 2 of the License, or (at your
+option) any later version.
+
+The MPFR Library is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
+License for more details.
+
+You should have received a copy of the GNU Library General Public License
+along with the MPFR Library; see the file COPYING.LIB.  If not, write to
+the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+MA 02111-1307, USA. */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include "gmp.h"
+#include "gmp-impl.h"
+#include "mpfr.h"
+#include "mpfr-impl.h"
+
+ /* The computation of hypot of x and y is done by
+
+    hypot(x,y)= sqrt(x^2+y^2) = z
+ */
+int mpfr_hypot _PROTO((mpfr_ptr, mpfr_srcptr,mpfr_srcptr, mp_rnd_t));
+
+int
+#if __STDC__
+mpfr_hypot (mpfr_ptr z, mpfr_srcptr x ,mpfr_srcptr y , mp_rnd_t rnd_mode) 
+#else
+mpfr_hypot (z, x,y, rnd_mode)
+     mpfr_ptr z;
+     mpfr_srcptr x;
+     mpfr_srcptr y;
+     mp_rnd_t rnd_mode;
+#endif
+{
+    
+    /* particular cases */
+
+    if (MPFR_IS_NAN(x) || MPFR_IS_NAN(y)) {  MPFR_SET_NAN(z); return 1; }
+    MPFR_CLEAR_NAN(z);
+
+    if (MPFR_IS_INF(x) || MPFR_IS_INF(y)){ 
+      MPFR_SET_INF(z);
+      if (MPFR_SIGN(z) < 0) MPFR_CHANGE_SIGN(z);
+      return 1;
+    }
+
+    MPFR_CLEAR_INF(z);
+  
+    if(!MPFR_NOTZERO(x)){
+      mpfr_set(z,y,rnd_mode);
+      if (MPFR_SIGN(z) < 0) MPFR_CHANGE_SIGN(z);
+      return 1;
+    }
+    if(!MPFR_NOTZERO(y)){
+      mpfr_set(z,x,rnd_mode);
+      if (MPFR_SIGN(z) < 0) MPFR_CHANGE_SIGN(z);
+      return 1;
+    }
+
+
+    /* General case */
+
+    {
+      /* Declaration of the intermediary variable */
+      mpfr_t t, te,ti;       
+
+      /* Flag calcul exacte */
+      int exact=0;
+
+      /* Declaration of the size variable */
+      mp_prec_t Nx = MPFR_PREC(x);   /* Precision of input variable */
+      mp_prec_t Ny = MPFR_PREC(y);   /* Precision of input variable */
+      mp_prec_t Nz = MPFR_PREC(z);   /* Precision of input variable */
+      
+      mp_prec_t Nt;   /* Precision of the intermediary variable */
+      mp_prec_t err;  /* Precision of error */
+      
+      /* compute the precision of intermediary variable */
+      Nt=MAX(MAX(Nx,Ny),Nz);
+
+      /* compute the size of intermediary variable -- see algorithms.ps */
+      Nt=Nt+2+_mpfr_ceil_log2(Nt);
+
+      /* initialise the intermediary variables */
+      mpfr_init(t);             
+      mpfr_init(te);             
+      mpfr_init(ti); 
+
+      /* Hypot */
+      do {
+        /* reactualisation of the precision */
+        mpfr_set_prec(t,Nt);             
+        mpfr_set_prec(te,Nt);             
+        mpfr_set_prec(ti,Nt);   
+
+        /* computations of hypot */
+        if(abs(mpfr_mul(te,x,x,GMP_RNDN)))         /* x^2 */
+          exact=1;
+        if(abs(mpfr_mul(ti,y,y,GMP_RNDN)))         /* y^2 */
+          exact=1;
+        if(abs(mpfr_add(t,te,ti,GMP_RNDD)))        /* x^2+y^2*/
+          exact=1;
+        if(abs(mpfr_sqrt(t,t,GMP_RNDN)))           /* sqrt(x^2+y^2)*/
+          exact=1;
+ 
+        /* estimation of the error */
+        err=Nt-(2);
+    
+        Nt += 10; 
+
+      } while ((mpfr_can_round(t,err,GMP_RNDN,rnd_mode,Nz)!=1) && exact);
+
+      mpfr_set(z,t,rnd_mode);
+      mpfr_clear(t);
+      mpfr_clear(ti);
+      mpfr_clear(te);
+
+    }
+    return 1;   
+}