Fix description of rounding to nearest in fixed point to take into

[pintos-anon] / doc / 44bsd.texi

diff --git a/doc/44bsd.texi b/doc/44bsd.texi
index 3bbce0d572c2a6b3cc051920fa7caa7906b439ae..fc619c1595cd367690815bda13e2070b6a934a1f 100644 (file)
--- a/doc/44bsd.texi
+++ b/doc/44bsd.texi
@@ -179,14 +179,13 @@ current value of @var{recent_cpu} decays to a weight of .1 in
 received ``recently,'' with the rate of decay inversely proportional to
 the number of threads competing for the CPU.
 
-Because of assumptions made by some of the tests, @var{recent_cpu} must
-be updated exactly when the system tick counter reaches a multiple of a
-second, that is, when @code{timer_ticks () % TIMER_FREQ == 0}, and not
-at any other time.
+Assumptions made by some of the tests require that updates to
+@var{recent_cpu} be made exactly when the system tick counter reaches a
+multiple of a second, that is, when @code{timer_ticks () % TIMER_FREQ ==
+0}, and not at any other time.
 
-Take note that @var{recent_cpu} can be a negative quantity for a thread
-with a negative @var{nice} value.  Negative values of @var{recent_cpu}
-are not changed to 0.
+The value of @var{recent_cpu} can be negative for a thread with a
+negative @var{nice} value.  Do not clamp negative @var{recent_cpu} to 0.
 
 You must implement @func{thread_get_recent_cpu}, for which there is a
 skeleton in @file{threads/thread.c}.
@@ -319,11 +318,12 @@ q}:
 @item Convert @code{n} to fixed point:
 @tab @code{n * f}
 
-@item Convert @code{x} to integer (rounding down):
+@item Convert @code{x} to integer (rounding toward zero):
 @tab @code{x / f}
 
 @item Convert @code{x} to integer (rounding to nearest):
-@tab @code{(x + f / 2) / f}
+@tab @code{(x + f / 2) / f} if @code{x >= 0}, @*
+@code{(x - f / 2) / f} if @code{x <= 0}.
 
 @item Add @code{x} and @code{y}:
 @tab @code{x + y}