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authorKevin B Kenny <kennykb@acm.org>2008-10-05 21:25:23 (GMT)
committerKevin B Kenny <kennykb@acm.org>2008-10-05 21:25:23 (GMT)
commit7a8890b848e2ed877f22708fa8aeebf5c22b129a (patch)
tree4e5b2800c54f1cd9167bea20db0760443baa0d39
parent6baa5b8d5a6b70470cad4964945c2027b381011f (diff)
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* libtommath/bn_mp_sqrt.c (bn_mp_sqrt): Handle the case where
* tests/expr.test (expr-47.13): a number's square root is between n<<DIGIT_BIT and n<<DIGIT_BIT+1. [Bug 2143288] Thanks to Malcolm Boffey (malcolm.boffey@virgin.net) for the patch.
-rw-r--r--ChangeLog8
-rw-r--r--libtommath/bn_mp_sqrt.c25
-rw-r--r--tests/expr.test23
3 files changed, 51 insertions, 5 deletions
diff --git a/ChangeLog b/ChangeLog
index 4cda4c0..23eb041 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2008-10-05 Kevin B, Kenny <kennykb@acm.org>
+
+ * libtommath/bn_mp_sqrt.c (bn_mp_sqrt): Handle the case where
+ * tests/expr.test (expr-47.13): a number's square root
+ is between n<<DIGIT_BIT and n<<DIGIT_BIT+1. [Bug 2143288]
+ Thanks to Malcolm Boffey (malcolm.boffey@virgin.net) for
+ the patch.
+
2008-10-02 Joe Mistachkin <joe@mistachkin.com>
* tools/man2help2.tcl: Integrated patches from Harald Oehlmann.
diff --git a/libtommath/bn_mp_sqrt.c b/libtommath/bn_mp_sqrt.c
index 3aa0f38..aab357a 100644
--- a/libtommath/bn_mp_sqrt.c
+++ b/libtommath/bn_mp_sqrt.c
@@ -27,7 +27,7 @@ int mp_sqrt(mp_int *arg, mp_int *ret)
mp_int t1,t2;
int i, j, k;
#ifndef NO_FLOATING_POINT
- double d;
+ volatile double d;
mp_digit dig;
#endif
@@ -64,12 +64,29 @@ int mp_sqrt(mp_int *arg, mp_int *ret)
for (k = arg->used-1; k >= j; --k) {
d = ldexp(d, DIGIT_BIT) + (double) (arg->dp[k]);
}
+
+ /*
+ * At this point, d is the nearest floating point number to the most
+ * significant 1 or 2 mp_digits of arg. Extract its square root.
+ */
+
d = sqrt(d);
+
+ /* dig is the most significant mp_digit of the square root */
+
dig = (mp_digit) ldexp(d, -DIGIT_BIT);
+
+ /*
+ * If the most significant digit is nonzero, find the next digit down
+ * by subtracting DIGIT_BIT times thie most significant digit.
+ * Subtract one from the result so that our initial estimate is always
+ * low.
+ */
+
if (dig) {
t1.used = i+2;
d -= ldexp((double) dig, DIGIT_BIT);
- if (d != 0.0) {
+ if (d >= 1.0) {
t1.dp[i+1] = dig;
t1.dp[i] = ((mp_digit) d) - 1;
} else {
@@ -126,5 +143,5 @@ E2: mp_clear(&t1);
/* $Source: /root/tcl/repos-to-convert/tcl/libtommath/bn_mp_sqrt.c,v $ */
/* Based on Tom's 1.3 */
-/* $Revision: 1.5 $ */
-/* $Date: 2006/12/01 05:48:23 $ */
+/* $Revision: 1.5.4.1 $ */
+/* $Date: 2008/10/05 21:25:23 $ */
diff --git a/tests/expr.test b/tests/expr.test
index d0aaadb..30aebc6 100644
--- a/tests/expr.test
+++ b/tests/expr.test
@@ -10,7 +10,7 @@
# See the file "license.terms" for information on usage and redistribution
# of this file, and for a DISCLAIMER OF ALL WARRANTIES.
#
-# RCS: @(#) $Id: expr.test,v 1.72 2008/03/10 16:18:55 dgp Exp $
+# RCS: @(#) $Id: expr.test,v 1.72.2.1 2008/10/05 21:25:23 kennykb Exp $
if {[lsearch [namespace children] ::tcltest] == -1} {
package require tcltest 2.1
@@ -6770,6 +6770,7 @@ test expr-47.11 {isqrt of zero} {
test expr-47.12 {isqrt of various sizes of integer} {
set faults 0
+ set trouble {}
for {set i 0} {$faults < 10 && $i <= 1024} {incr i} {
set root [expr {1 << $i}]
set rm1 [expr {$root - 1}]
@@ -6796,6 +6797,26 @@ test expr-47.12 {isqrt of various sizes of integer} {
set trouble
} {}
+test expr-47.13 {isqrt and floating point rounding (Bug 2143288)} {
+ set trouble {}
+ set faults 0
+ for {set i 0} {$i < 29 && $faults < 10} {incr i} {
+ for {set j 0} {$j <= $i} {incr j} {
+ set k [expr {isqrt((1<<56)+(1<<$i)+(1<<$j))}]
+ if {$k != (1<<28)} {
+ append trouble "i = $i, j = $j, k = $k\n"
+ incr faults
+ }
+ }
+ set k [expr {isqrt((1<<56)+(1<<29)+(1<<$i))}]
+ if {$k != (1<<28)+1} {
+ append trouble "i = $i, k = $k\n"
+ incr faults
+ }
+ }
+ set trouble
+} {}
+
test expr-48.1 {Bug 1770224} {
expr {-0x8000000000000001 >> 0x8000000000000000}
} -1