1 files changed, 134 insertions, 0 deletions
diff --git a/mpfr/acosh.c b/mpfr/acosh.c
new file mode 100644
index 000000000..6953b9b37
--- /dev/null
+++ b/mpfr/acosh.c
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+/* mpfr_acosh -- Inverse Hyperbolic Cosine of Unsigned Integer Number
+
+Copyright (C) 2001 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 Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 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 Lesser General Public
+License for more details.
+
+You should have received a copy of the GNU Lesser 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 "gmp.h"
+#include "gmp-impl.h"
+#include "mpfr.h"
+#include "mpfr-impl.h"
+
+ /* The computation of acosh is done by
+
+    acosh= ln(x+sqrt(x-1)*sqrt(x+1))
+ */
+
+int
+mpfr_acosh (mpfr_ptr y, mpfr_srcptr x , mp_rnd_t rnd_mode) 
+{
+    
+  int inexact =0;
+  int comp;
+
+  if (MPFR_IS_NAN(x)) 
+    {
+      MPFR_SET_NAN(y); 
+      return 1; 
+    }
+    
+  comp=mpfr_cmp_ui(x,1);
+
+  if(comp < 0)
+    {
+      MPFR_SET_NAN(y); 
+      return(1);
+    }
+  MPFR_CLEAR_NAN(y);
+
+  if(comp == 0)
+    {
+      MPFR_SET_ZERO(y); /* acosh(1) = 0 */
+      return(0);
+    }
+  
+  if (MPFR_IS_INF(x))
+    { 
+      MPFR_SET_INF(y);
+      if (MPFR_SIGN(y) < 0) 
+        MPFR_CHANGE_SIGN(y);
+      return 1;
+    }
+
+  MPFR_CLEAR_INF(y);
+
+  /* General case */
+  {
+    /* Declaration of the intermediary variable */
+    mpfr_t t, te,ti;       
+    
+    /* 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 Nt;   /* Precision of the intermediary variable */
+    int err;  /* Precision of error */
+                
+    /* compute the precision of intermediary variable */
+    Nt=MAX(Nx,Ny);
+    /* the optimal number of bits : see algorithms.ps */
+    Nt=Nt+4+_mpfr_ceil_log2(Nt);
+
+    /* initialise of intermediary	variable */
+    mpfr_init(t);             
+    mpfr_init(te);             
+    mpfr_init(ti);                    
+
+    /* First computation of cosh */
+    do {
+
+      /* reactualisation of the precision */
+      mpfr_set_prec(t,Nt);             
+      mpfr_set_prec(te,Nt);             
+      mpfr_set_prec(ti,Nt);             
+
+      /* compute acosh */
+      mpfr_mul(te,x,x,GMP_RNDD);  /* (x^2) */
+      mpfr_sub_ui(ti,te,1,GMP_RNDD);  /* (x^2-1) */
+      mpfr_sqrt(t,ti,GMP_RNDN);     /* sqrt(x^2-1) */
+      mpfr_add(t,t,x,GMP_RNDN);    /* sqrt(x^2-1)+x */
+      mpfr_log(t,t,GMP_RNDN);        /* ln(sqrt(x^2-1)+x)*/
+
+      /* estimation of the error see- algorithms.ps*/
+      /*err=Nt-_mpfr_ceil_log2(0.5+pow(2,2-MPFR_EXP(t))+pow(2,1+MPFR_EXP(te)-MPFR_EXP(ti)-MPFR_EXP(t)));*/
+      err=Nt-(-1+2*MAX(2+MAX(2-MPFR_EXP(t),1+MPFR_EXP(te)-MPFR_EXP(ti)-MPFR_EXP(t)),0));
+
+      /* actualisation of the precision */
+      Nt += 10;
+
+    } while ((err<0) ||!mpfr_can_round(t,err,GMP_RNDN,rnd_mode,Ny));
+ 
+    inexact = mpfr_set(y,t,rnd_mode);
+
+    mpfr_clear(t);
+    mpfr_clear(ti);
+    mpfr_clear(te);
+  }
+  return inexact;
+}
+
+
+
+
+
+
+
+
+
+
+