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authorPetr Baudis <pasky@suse.cz>2011-09-09 22:16:10 -0400
committerUlrich Drepper <drepper@gmail.com>2011-09-09 22:16:10 -0400
commit1248c1c41508387ff282b208636737e8cdc9b5b0 (patch)
treef2de6f410de805293483964814aa29efefbe8daa /sysdeps/ieee754/ldbl-128
parentf19009c1551a396ee8eff96a83254243ce25a090 (diff)
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Fix jn precision
Diffstat (limited to 'sysdeps/ieee754/ldbl-128')
-rw-r--r--sysdeps/ieee754/ldbl-128/e_jnl.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/sysdeps/ieee754/ldbl-128/e_jnl.c b/sysdeps/ieee754/ldbl-128/e_jnl.c
index a4a4e24cf5..a7f6772c08 100644
--- a/sysdeps/ieee754/ldbl-128/e_jnl.c
+++ b/sysdeps/ieee754/ldbl-128/e_jnl.c
@@ -285,7 +285,16 @@ __ieee754_jnl (n, x)
 		    }
 		}
 	    }
-	  b = (t * __ieee754_j0l (x) / b);
+	  /* j0() and j1() suffer enormous loss of precision at and
+	   * near zero; however, we know that their zero points never
+	   * coincide, so just choose the one further away from zero.
+	   */
+	  z = __ieee754_j0l (x);
+	  w = __ieee754_j1l (x);
+	  if (fabsl (z) >= fabsl (w))
+	    b = (t * z / b);
+	  else
+	    b = (t * w / a);
 	}
     }
   if (sgn == 1)