math: add large exact float rounding tests

This CL adds trunc,ceil,floor tests for large exact float.

Change-Id: Ib7ffec1d2d50d2ac955398a3dd0fd06d494fcf4f
Reviewed-on: https://go-review.googlesource.com/c/go/+/601095
Auto-Submit: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Keith Randall <khr@golang.org>

diff --git a/src/math/all_test.go b/src/math/all_test.go
index af3c38c2a690dda7da30e189bc58861c7c737849..c253b7bc025d34fa6ad63dbacd8cd64d08af11aa 100644 (file)
--- a/src/math/all_test.go
+++ b/src/math/all_test.go
@@ -899,8 +899,17 @@ var vfceilSC = []float64{
        0,
        Inf(1),
        NaN(),
+       1<<52 - 1,
+       1<<52 - 0.5, // largest fractional float64
+       1 << 52,
+       -1 << 52,
+       -1<<52 + 0.5, // smallest fractional float64
+       -1<<52 + 1,
+       1 << 53,
+       -1 << 53,
 }
-var ceilSC = []float64{
+
+var ceilBaseSC = []float64{
        Inf(-1),
        Copysign(0, -1),
        0,
@@ -908,6 +917,39 @@ var ceilSC = []float64{
        NaN(),
 }
 
+var ceilSC = append(ceilBaseSC,
+       1<<52-1,
+       1<<52,
+       1<<52,
+       -1<<52,
+       -1<<52+1,
+       -1<<52+1,
+       1<<53,
+       -1<<53,
+)
+
+var floorSC = append(ceilBaseSC,
+       1<<52-1,
+       1<<52-1,
+       1<<52,
+       -1<<52,
+       -1<<52,
+       -1<<52+1,
+       1<<53,
+       -1<<53,
+)
+
+var truncSC = append(ceilBaseSC,
+       1<<52-1,
+       1<<52-1,
+       1<<52,
+       -1<<52,
+       -1<<52+1,
+       -1<<52+1,
+       1<<53,
+       -1<<53,
+)
+
 var vfcopysignSC = []float64{
        Inf(-1),
        Inf(1),
@@ -2489,8 +2531,8 @@ func TestFloor(t *testing.T) {
                }
        }
        for i := 0; i < len(vfceilSC); i++ {
-               if f := Floor(vfceilSC[i]); !alike(ceilSC[i], f) {
-                       t.Errorf("Floor(%g) = %g, want %g", vfceilSC[i], f, ceilSC[i])
+               if f := Floor(vfceilSC[i]); !alike(floorSC[i], f) {
+                       t.Errorf("Floor(%g) = %g, want %g", vfceilSC[i], f, floorSC[i])
                }
        }
 }
@@ -3034,8 +3076,8 @@ func TestTrunc(t *testing.T) {
                }
        }
        for i := 0; i < len(vfceilSC); i++ {
-               if f := Trunc(vfceilSC[i]); !alike(ceilSC[i], f) {
-                       t.Errorf("Trunc(%g) = %g, want %g", vfceilSC[i], f, ceilSC[i])
+               if f := Trunc(vfceilSC[i]); !alike(truncSC[i], f) {
+                       t.Errorf("Trunc(%g) = %g, want %g", vfceilSC[i], f, truncSC[i])
                }
        }
 }