Merge "CPU statistics library"

1 files changed, 81 insertions, 0 deletions

diff --git a/libs/cpustats/CentralTendencyStatistics.cpp b/libs/cpustats/CentralTendencyStatistics.cpp
new file mode 100644
index 000000000000..42ab62b4efd7
--- /dev/null
+++ b/libs/cpustats/CentralTendencyStatistics.cpp
@@ -0,0 +1,81 @@
+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <stdlib.h>
+
+#include <cpustats/CentralTendencyStatistics.h>
+
+void CentralTendencyStatistics::sample(double x)
+{
+    // update min and max
+    if (x < mMinimum)
+        mMinimum = x;
+    if (x > mMaximum)
+        mMaximum = x;
+    // Knuth
+    if (mN == 0) {
+        mMean = 0;
+    }
+    ++mN;
+    double delta = x - mMean;
+    mMean += delta / mN;
+    mM2 += delta * (x - mMean);
+}
+
+void CentralTendencyStatistics::reset()
+{
+    mMean = NAN;
+    mMedian = NAN;
+    mMinimum = INFINITY;
+    mMaximum = -INFINITY;
+    mN = 0;
+    mM2 = 0;
+    mVariance = NAN;
+    mVarianceKnownForN = 0;
+    mStddev = NAN;
+    mStddevKnownForN = 0;
+}
+
+double CentralTendencyStatistics::variance() const
+{
+    double variance;
+    if (mVarianceKnownForN != mN) {
+        if (mN > 1) {
+            // double variance_n = M2/n;
+            variance = mM2 / (mN - 1);
+        } else {
+            variance = NAN;
+        }
+        mVariance = variance;
+        mVarianceKnownForN = mN;
+    } else {
+        variance = mVariance;
+    }
+    return variance;
+}
+
+double CentralTendencyStatistics::stddev() const
+{
+    double stddev;
+    if (mStddevKnownForN != mN) {
+        stddev = sqrt(variance());
+        mStddev = stddev;
+        mStddevKnownForN = mN;
+    } else {
+        stddev = mStddev;
+    }
+    return stddev;
+}