[cmucl-commit] [git] CMU Common Lisp branch master updated. snapshot-2014-08-9-g375ce21

[Raymond Toy]

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- Log -----------------------------------------------------------------
commit 375ce218ab639fbc0b433942dbb7398a0bcd0177
Author: Raymond Toy <toy.raymond at gmail.com>
Date:   Thu Aug 14 21:06:20 2014 -0700

    Fix ticket:106 by returning the correctly rounded value.
    
     * src/lisp/e_exp.c:
       * Add special case to return the correctly rounded value of exp(1).
     * tests/trac.lisp:
       * Add test that the correct value is returned.
       * Add test that exp(x) is still monotonic around x = 1.
     * src/general-info/release-20f.txt:
       * Update.

diff --git a/src/general-info/release-20f.txt b/src/general-info/release-20f.txt
index 265b0b5..92df6fa 100644
--- a/src/general-info/release-20f.txt
+++ b/src/general-info/release-20f.txt
@@ -97,6 +97,8 @@ New in this release:
     * In some situations KERNEL:DOUBLE-FLOAT-BITS on x86 would cause a
       segfault. This has been fixed.
     * For linux, motifd is no longer a 64-bit app.
+    * (exp 1d0) now returns the correctly rounded value of
+      e. Previously, it was off by one bit.
 
   * Trac Tickets:
     * Ticket #90 fixed.
@@ -111,6 +113,7 @@ New in this release:
     * Ticket #84 fixed on x86.
     * Ticket #105 fixed.
     * Ticket #101 fixed.
+    * Ticket #106 fixed.
 
   * Other changes:
 
diff --git a/src/lisp/e_exp.c b/src/lisp/e_exp.c
index 8233bc3..8b7ff6d 100644
--- a/src/lisp/e_exp.c
+++ b/src/lisp/e_exp.c
@@ -111,6 +111,17 @@ P5   =  4.13813679705723846039e-08; /* 0x3E663769, 0x72BEA4D0 */
 	unsigned hx;
 	union { int i[2]; double d; } ux;
 
+        /*
+         * CMUCL addition: Return correctly rounded value for
+         * exp(1). There are tests to verify that exp(x) is still
+         * monotonic around exp(1), so this change doens't break
+         * anything.
+         */
+        if (x == 1) {
+            /* Return the correctly rounded value for x = 1 */
+            return 2.718281828459045;
+        }
+
 	ux.d = x;
 	hx  = ux.i[HIWORD];	/* high word of x */
 	xsb = (hx>>31)&1;		/* sign bit of x */
diff --git a/tests/trac.lisp b/tests/trac.lisp
index 8253bc2..2bf420d 100644
--- a/tests/trac.lisp
+++ b/tests/trac.lisp
@@ -425,4 +425,14 @@ No dispatch function defined for #\\W.")
 		(read-string-fn "#\wtf")))
 			   
 
-  
\ No newline at end of file
+(define-test trac.106
+  (:tag :trac)
+  ;; Verify the value is correct
+  (assert-equal 2.718281828459045d0
+		(exp 1d0))
+  ;; Verify that exp is still monotonic around 1
+  (assert-true (<= (exp (1- double-float-negative-epsilon))
+		   (exp 1d0)
+		   (exp (1+ double-float-epsilon)))))
+
+

-----------------------------------------------------------------------

Summary of changes:
 src/general-info/release-20f.txt |    3 +++
 src/lisp/e_exp.c                 |   11 +++++++++++
 tests/trac.lisp                  |   12 +++++++++++-
 3 files changed, 25 insertions(+), 1 deletion(-)


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