[Android] setRepeating() の誤差と setExact() setWindow()

Android 19 からAlarmMangerでの、set()、setRepeating()などの時間経過の誤差が大きくなりました。（inexact になったとあります）
理由は、バッテリー電力消費量を改善するためのようですが、実際どの程度なのか試してみました。

setRepeating(), set()のinexact

確かに、毎朝７時のアラームが７時１分であれば、多少は許容される場合もあるでしょうが
そもそも誤差がどれだけなのかよくわかりません。OSに依存させているというのは、けっこう出たとこ勝負ではないでょうか。
　
テストを実施してみました。
Activity から Service を呼び、AlarmManager にそれぞれのメソッドをセットします
アラーム起動は１秒後で、その後１分間隔で繰り返すテストです
Nexus7 2013 を使用
またスマホはwakeupの状態
targetSdkVersion = 25 です
　

setRepeating

03-14 11:28:38.185    8451-8451/com.example.testalarm D/Service﹕ received
03-14 11:29:38.206    8451-8451/com.example.testalarm D/Service﹕ received
03-14 11:30:38.198    8451-8451/com.example.testalarm D/Service﹕ received
03-14 11:31:43.034    8451-8451/com.example.testalarm D/Service﹕ received
03-14 11:33:01.045    8451-8451/com.example.testalarm D/Service﹕ received
03-14 11:33:53.729    8451-8451/com.example.testalarm D/Service﹕ received
03-14 11:34:53.735    8451-8451/com.example.testalarm D/Service﹕ received
03-14 11:35:53.735    8451-8451/com.example.testalarm D/Service﹕ received
03-14 11:37:14.438    8451-8451/com.example.testalarm D/Service﹕ received
03-14 11:37:38.209    8451-8451/com.example.testalarm D/Service﹕ received

03-14 11:28:38.185 8451-8451/com.example.testalarm D/Service﹕ received

03-14 11:29:38.206 8451-8451/com.example.testalarm D/Service﹕ received

03-14 11:30:38.198 8451-8451/com.example.testalarm D/Service﹕ received

03-14 11:31:43.034 8451-8451/com.example.testalarm D/Service﹕ received

03-14 11:33:01.045 8451-8451/com.example.testalarm D/Service﹕ received

03-14 11:33:53.729 8451-8451/com.example.testalarm D/Service﹕ received

03-14 11:34:53.735 8451-8451/com.example.testalarm D/Service﹕ received

03-14 11:35:53.735 8451-8451/com.example.testalarm D/Service﹕ received

03-14 11:37:14.438 8451-8451/com.example.testalarm D/Service﹕ received

03-14 11:37:38.209 8451-8451/com.example.testalarm D/Service﹕ received

相当ばらついています
1分間隔ですが24秒後にアラームが出てることもあります
　

　

set

setは単発アラームなので、Serviceでアラーム起動後、次のアラームを設定する方法をとりました

03-13 22:38:31.658  11912-11912/com.example.testalarm D/Service﹕ received
03-13 22:39:36.340  11912-11912/com.example.testalarm D/Service﹕ received
03-13 22:40:36.377  11912-11912/com.example.testalarm D/Service﹕ received
03-13 22:41:55.403  11912-11912/com.example.testalarm D/Service﹕ received
03-13 22:42:56.364  11912-11912/com.example.testalarm D/Service﹕ received
03-13 22:43:56.410  11912-11912/com.example.testalarm D/Service﹕ received
03-13 22:45:01.056  11912-11912/com.example.testalarm D/Service﹕ received
03-13 22:46:01.094  11912-11912/com.example.testalarm D/Service﹕ received
03-13 22:47:01.125  11912-11912/com.example.testalarm D/Service﹕ received
03-13 22:48:01.993  11912-11912/com.example.testalarm D/Service﹕ received

03-13 22:38:31.658 11912-11912/com.example.testalarm D/Service﹕ received

03-13 22:39:36.340 11912-11912/com.example.testalarm D/Service﹕ received

03-13 22:40:36.377 11912-11912/com.example.testalarm D/Service﹕ received

03-13 22:41:55.403 11912-11912/com.example.testalarm D/Service﹕ received

03-13 22:42:56.364 11912-11912/com.example.testalarm D/Service﹕ received

03-13 22:43:56.410 11912-11912/com.example.testalarm D/Service﹕ received

03-13 22:45:01.056 11912-11912/com.example.testalarm D/Service﹕ received

03-13 22:46:01.094 11912-11912/com.example.testalarm D/Service﹕ received

03-13 22:47:01.125 11912-11912/com.example.testalarm D/Service﹕ received

03-13 22:48:01.993 11912-11912/com.example.testalarm D/Service﹕ received

　
毎回設定しているためか、setRepeating よりはマシですが
時々ズレます
　
　

setExact

03-14 12:27:08.585  11711-11711/com.example.testalarm D/Service﹕ received
03-14 12:28:08.606  11711-11711/com.example.testalarm D/Service﹕ received
03-14 12:29:08.626  11711-11711/com.example.testalarm D/Service﹕ received
03-14 12:30:08.636  11711-11711/com.example.testalarm D/Service﹕ received
03-14 12:31:08.641  11711-11711/com.example.testalarm D/Service﹕ received
03-14 12:32:08.659  11711-11711/com.example.testalarm D/Service﹕ received
03-14 12:33:08.686  11711-11711/com.example.testalarm D/Service﹕ received
03-14 12:34:08.706  11711-11711/com.example.testalarm D/Service﹕ received
03-14 12:35:08.726  11711-11711/com.example.testalarm D/Service﹕ received
03-14 12:36:08.760  11711-11711/com.example.testalarm D/Service﹕ received

03-14 12:27:08.585 11711-11711/com.example.testalarm D/Service﹕ received

03-14 12:28:08.606 11711-11711/com.example.testalarm D/Service﹕ received

03-14 12:29:08.626 11711-11711/com.example.testalarm D/Service﹕ received

03-14 12:30:08.636 11711-11711/com.example.testalarm D/Service﹕ received

03-14 12:31:08.641 11711-11711/com.example.testalarm D/Service﹕ received

03-14 12:32:08.659 11711-11711/com.example.testalarm D/Service﹕ received

03-14 12:33:08.686 11711-11711/com.example.testalarm D/Service﹕ received

03-14 12:34:08.706 11711-11711/com.example.testalarm D/Service﹕ received

03-14 12:35:08.726 11711-11711/com.example.testalarm D/Service﹕ received

03-14 12:36:08.760 11711-11711/com.example.testalarm D/Service﹕ received

　
setExact のReferenceでは
http://developer.android.com/reference/android/app/AlarmManager.html#setExact(int, long, android.app.PendingIntent)

This method is like set(int, long, PendingIntent), but does not permit the OS to adjust the delivery time. The alarm will be delivered as nearly as possible to the requested trigger time.

ということで、努力目標でしょうか
CPUに負荷がかかってしまうと確実ではないような感じですね
　

　

setWindow

window の幅は 1000 msec に設定
　

03-14 12:51:45.646  13586-13586/com.example.testalarm D/Service﹕ received
03-14 12:52:45.654  13586-13586/com.example.testalarm D/Service﹕ received
03-14 12:53:45.661  13586-13586/com.example.testalarm D/Service﹕ received
03-14 12:54:45.677  13586-13586/com.example.testalarm D/Service﹕ received
03-14 12:55:45.694  13586-13586/com.example.testalarm D/Service﹕ received
03-14 12:56:45.705  13586-13586/com.example.testalarm D/Service﹕ received
03-14 12:57:46.546  13586-13586/com.example.testalarm D/Service﹕ received
03-14 12:58:46.567  13586-13586/com.example.testalarm D/Service﹕ received
03-14 12:59:46.585  13586-13586/com.example.testalarm D/Service﹕ received
03-14 13:00:47.425  13586-13586/com.example.testalarm D/Service﹕ received

03-14 12:51:45.646 13586-13586/com.example.testalarm D/Service﹕ received

03-14 12:52:45.654 13586-13586/com.example.testalarm D/Service﹕ received

03-14 12:53:45.661 13586-13586/com.example.testalarm D/Service﹕ received

03-14 12:54:45.677 13586-13586/com.example.testalarm D/Service﹕ received

03-14 12:55:45.694 13586-13586/com.example.testalarm D/Service﹕ received

03-14 12:56:45.705 13586-13586/com.example.testalarm D/Service﹕ received

03-14 12:57:46.546 13586-13586/com.example.testalarm D/Service﹕ received

03-14 12:58:46.567 13586-13586/com.example.testalarm D/Service﹕ received

03-14 12:59:46.585 13586-13586/com.example.testalarm D/Service﹕ received

03-14 13:00:47.425 13586-13586/com.example.testalarm D/Service﹕ received

　
SetWindow のReferenceでは
http://developer.android.com/reference/android/app/AlarmManager.html#setWindow(int, long, long, android.app.PendingIntent)

Schedule an alarm to be delivered within a given window of time. This method is similar to set(int, long, PendingIntent), but allows the application to precisely control the degree to which its delivery might be adjusted by the OS.

windowの範囲内であればOSが調整してくれる（たぶん）
ということですね
　

　
window の範囲内でアラームが出ていますが
繰り返しによる遅れがだんだん積み重なっています
setWindow、setExact 以外に繰り返しのAPIがないようです

x setExactRepeatingというのが無い

setWindowがとりあえず、バッテリー消費と時間精度の妥協策でしょうか