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authorJan Arve Saether <jan-arve.saether@digia.com>2013-07-31 15:43:09 +0200
committerThe Qt Project <gerrit-noreply@qt-project.org>2013-09-27 07:57:23 +0200
commite37001aad7f6e4bbad250addba033f1eaf97d566 (patch)
treee83a70da7f50edd967128f84df18287e805e30a9 /tests/auto/corelib/global/qnumeric/tst_qnumeric.cpp
parent88999e9ea037ee79557d0c012ad9fdfc72fb5ece (diff)
Say hello to qFloatDistance()
This function is useful if a floating point comparison requires a certain precision. The return value can be considered as the precision. For instance, if you want to compare two 32-bit floating point values and all you need is a 24-bit precision, you can use this function like this: if (qFloatDistance(a,b) < (1 << 7)) { // The last 7 bits are not // significant // precise enough } Task-number: QTBUG-32632 Change-Id: I020a58d2f9f9452ac3c510b4bb560dc806f0d93c Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com> Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Diffstat (limited to 'tests/auto/corelib/global/qnumeric/tst_qnumeric.cpp')
-rw-r--r--tests/auto/corelib/global/qnumeric/tst_qnumeric.cpp93
1 files changed, 93 insertions, 0 deletions
diff --git a/tests/auto/corelib/global/qnumeric/tst_qnumeric.cpp b/tests/auto/corelib/global/qnumeric/tst_qnumeric.cpp
index 20f99e9191..36e01a0ccd 100644
--- a/tests/auto/corelib/global/qnumeric/tst_qnumeric.cpp
+++ b/tests/auto/corelib/global/qnumeric/tst_qnumeric.cpp
@@ -44,6 +44,7 @@
#include <QtGlobal>
#include <math.h>
+#include <float.h>
class tst_QNumeric: public QObject
{
@@ -53,6 +54,10 @@ private slots:
void fuzzyCompare_data();
void fuzzyCompare();
void qNan();
+ void floatDistance_data();
+ void floatDistance();
+ void floatDistance_double_data();
+ void floatDistance_double();
};
void tst_QNumeric::fuzzyCompare_data()
@@ -121,5 +126,93 @@ void tst_QNumeric::qNan()
QVERIFY(qFuzzyCompare(1/inf, 0.0));
}
+void tst_QNumeric::floatDistance_data()
+{
+ QTest::addColumn<float>("val1");
+ QTest::addColumn<float>("val2");
+ QTest::addColumn<quint32>("expectedDistance");
+
+ // exponent: 8 bits
+ // mantissa: 23 bits
+ const quint32 number_of_denormals = (1 << 23) - 1; // Set to 0 if denormals are not included
+
+ quint32 _0_to_1 = quint32((1 << 23) * 126 + 1 + number_of_denormals); // We need +1 to include the 0
+ quint32 _1_to_2 = quint32(1 << 23);
+
+ // We don't need +1 because FLT_MAX has all bits set in the mantissa. (Thus mantissa
+ // have not wrapped back to 0, which would be the case for 1 in _0_to_1
+ quint32 _0_to_FLT_MAX = quint32((1 << 23) * 254) + number_of_denormals;
+
+ quint32 _0_to_FLT_MIN = 1 + number_of_denormals;
+ QTest::newRow("[0,FLT_MIN]") << 0.F << FLT_MIN << _0_to_FLT_MIN;
+ QTest::newRow("[0,FLT_MAX]") << 0.F << FLT_MAX << _0_to_FLT_MAX;
+ QTest::newRow("[1,1.5]") << 1.0F << 1.5F << quint32(1 << 22);
+ QTest::newRow("[0,1]") << 0.F << 1.0F << _0_to_1;
+ QTest::newRow("[0.5,1]") << 0.5F << 1.0F << quint32(1 << 23);
+ QTest::newRow("[1,2]") << 1.F << 2.0F << _1_to_2;
+ QTest::newRow("[-1,+1]") << -1.F << +1.0F << 2 * _0_to_1;
+ QTest::newRow("[-1,0]") << -1.F << 0.0F << _0_to_1;
+ QTest::newRow("[-1,FLT_MAX]") << -1.F << FLT_MAX << _0_to_1 + _0_to_FLT_MAX;
+ QTest::newRow("[-2,-1") << -2.F << -1.F << _1_to_2;
+ QTest::newRow("[-1,-2") << -1.F << -2.F << _1_to_2;
+ QTest::newRow("[FLT_MIN,FLT_MAX]") << FLT_MIN << FLT_MAX << _0_to_FLT_MAX - _0_to_FLT_MIN;
+ QTest::newRow("[-FLT_MAX,FLT_MAX]") << -FLT_MAX << FLT_MAX << (2*_0_to_FLT_MAX);
+ float denormal = FLT_MIN;
+ denormal/=2.0F;
+ QTest::newRow("denormal") << 0.F << denormal << _0_to_FLT_MIN/2;
+}
+
+void tst_QNumeric::floatDistance()
+{
+ QFETCH(float, val1);
+ QFETCH(float, val2);
+ QFETCH(quint32, expectedDistance);
+ QCOMPARE(qFloatDistance(val1, val2), expectedDistance);
+}
+
+void tst_QNumeric::floatDistance_double_data()
+{
+ QTest::addColumn<double>("val1");
+ QTest::addColumn<double>("val2");
+ QTest::addColumn<quint64>("expectedDistance");
+
+ // exponent: 11 bits
+ // mantissa: 52 bits
+ const quint64 number_of_denormals = (Q_UINT64_C(1) << 52) - 1; // Set to 0 if denormals are not included
+
+ quint64 _0_to_1 = (Q_UINT64_C(1) << 52) * ((1 << (11-1)) - 2) + 1 + number_of_denormals; // We need +1 to include the 0
+ quint64 _1_to_2 = Q_UINT64_C(1) << 52;
+
+ // We don't need +1 because DBL_MAX has all bits set in the mantissa. (Thus mantissa
+ // have not wrapped back to 0, which would be the case for 1 in _0_to_1
+ quint64 _0_to_DBL_MAX = quint64((Q_UINT64_C(1) << 52) * ((1 << 11) - 2)) + number_of_denormals;
+
+ quint64 _0_to_DBL_MIN = 1 + number_of_denormals;
+ QTest::newRow("[0,DBL_MIN]") << 0.0 << DBL_MIN << _0_to_DBL_MIN;
+ QTest::newRow("[0,DBL_MAX]") << 0.0 << DBL_MAX << _0_to_DBL_MAX;
+ QTest::newRow("[1,1.5]") << 1.0 << 1.5 << (Q_UINT64_C(1) << 51);
+ QTest::newRow("[0,1]") << 0.0 << 1.0 << _0_to_1;
+ QTest::newRow("[0.5,1]") << 0.5 << 1.0 << (Q_UINT64_C(1) << 52);
+ QTest::newRow("[1,2]") << 1.0 << 2.0 << _1_to_2;
+ QTest::newRow("[-1,+1]") << -1.0 << +1.0 << 2 * _0_to_1;
+ QTest::newRow("[-1,0]") << -1.0 << 0.0 << _0_to_1;
+ QTest::newRow("[-1,DBL_MAX]") << -1.0 << DBL_MAX << _0_to_1 + _0_to_DBL_MAX;
+ QTest::newRow("[-2,-1") << -2.0 << -1.0 << _1_to_2;
+ QTest::newRow("[-1,-2") << -1.0 << -2.0 << _1_to_2;
+ QTest::newRow("[DBL_MIN,DBL_MAX]") << DBL_MIN << DBL_MAX << _0_to_DBL_MAX - _0_to_DBL_MIN;
+ QTest::newRow("[-DBL_MAX,DBL_MAX]") << -DBL_MAX << DBL_MAX << (2*_0_to_DBL_MAX);
+ double denormal = DBL_MIN;
+ denormal/=2.0;
+ QTest::newRow("denormal") << 0.0 << denormal << _0_to_DBL_MIN/2;
+}
+
+void tst_QNumeric::floatDistance_double()
+{
+ QFETCH(double, val1);
+ QFETCH(double, val2);
+ QFETCH(quint64, expectedDistance);
+ QCOMPARE(qFloatDistance(val1, val2), expectedDistance);
+}
+
QTEST_APPLESS_MAIN(tst_QNumeric)
#include "tst_qnumeric.moc"