My computer starts up everyday at the same time

Question

Friends, the first (maybe a couple) values generated from the following PRNG are either 0 or close to it no matter the seed. Is there a way this can be primed with a constructor or even better, without having to burn a couple of values?

type PRNGXXX(seed) =
    let mutable s : uint64[] =  Array.zeroCreate 2

    let rotl(x : uint64, k : int) =
        (x <<< k) ||| (x >>> (64 - k))

    do s.[1] <- uint64 seed

    let sample() : uint64 =
        let s0 : uint64 = s.[0]
        let mutable s1 : uint64 = s.[1]
        let result : uint64 = s0 + s1

        s1 <- s1 ^^^ s0
        s.[0] <- rotl(s0, 24) ^^^ s1 ^^^ (s1 <<< 16)
        s.[1] <- rotl(s1, 37)

        result

    member x.NextDouble() = (float (sample())) / float System.UInt64.MaxValue

Translated from C++ at http://xoshiro.di.unimi.it/xoroshiro128plus.c

#include <stdint.h>

static inline uint64_t rotl(const uint64_t x, int k) {
    return (x << k) | (x >> (64 - k));
}

static uint64_t s[2];

uint64_t next(void) {
    const uint64_t s0 = s[0];
    uint64_t s1 = s[1];
    const uint64_t result = s0 + s1;

    s1 ^= s0;
    s[0] = rotl(s0, 24) ^ s1 ^ (s1 << 16); // a, b
    s[1] = rotl(s1, 37); // c

    return result;
}

Solution 1

Try this first:

• Start an elevated command prompt. (Start, run, type cmd. Cmd.exe should appear in the list. Right click on it and select 'run as administrator'.
• In the large black screen type powercfg -waketimers

With a bit of luck this will already show you the timer which is set to wake windows.

If it does not list anything (such as in the example above) proceed to check the event log.

• Go to [start] [run] and type eventvwr.msc
• Open windows log
• Select system

There are a lot of entries here. Lets limit our view with a right click on 'system' and selecting Filter Current Log [SIC].

We are looking for power related items, so go to Event sources and select Power-Troubleshooter and click on [OK]

The view should now contain a lot less items. If you are lucky it contains a line such as:

The system has resumed from sleep

Sleep time 2012-10-21-typeitallovermeh
Wake time 2012-10-21-yayaydydyay
Wake source: Device-HID-compliant mouse

If you do not have a cat which plays with your mouse you will likely find another reason here. E.g. wake on LAN activity.

Once you know the reason you can counter it. Usually by going to the device manager and removing the 'allow this device to wake the computer`.

Other likely candidates not solved via the device manager are:

• Windows update. (It can be configured update your computer automatically. It can boot the laptop do do this, so check this option first. Especially if it happens at 3AM which is its default time).
• The BIOS. Some include an option to wake the computer at a specific time. This seems an option which is rarely present on frugal laptop BIOSses, but you will find it in allmost all server and workstations.

Solution 2

There are only two things that come to mind:

1. In the BIOS you have a setting set to power on the computer at that time.
2. There may be a system on your network sending out a Wake-on-LAN packet at a set time and your laptop is set to accept Wake-on-LAN packets.

Comments

[Blaine]

Starting up from being completely off, or waking up from sleep mode? The former is a BIOS setting, while the latter is an OS setting

[appy]

thanks it was the windows updates after all this is a very descriptive helpful post

[professor bigglesworth]

problem solved. thanks. does msft open source implementation of System.Random()? googling around suggests mersenne_twister_engine but can't seem to find the implementation.

[rmunn]

.Net Framework implementation: github.com/Microsoft/referencesource/blob/master/mscorlib/… and .Net Core implementation: github.com/dotnet/corefx/blob/master/src/Common/src/CoreLib/‌​…