turing machines – Can I apply the Rice theorem to determine the decidability status of these languages?

I came across the following languages:

  1. A Turing machine prints a particular letter.
  2. A Turing machine calculates the products from two numbers

I've suggested that I can use the Rice Theorem to decide if it's decidable or undecidable.

  1. Not all machine languages ​​have a specific letter, so the property is not trivial and therefore undecidable.
  2. Not all machine languages ​​deal with running two-numbered products, so this property is not trivial and therefore not decidable.

Undoubtedly, the Rissatz can be applied to languages ​​of Turing machines, not to the behavior or properties of Turing machines themselves or anything else that does not relate to "only" languages ​​they accept. I have tried to interpret given problems as if they were talking about the languages ​​accepted by these Turing machines, so that I can apply Rice's theorem to determine their decidability status. Am I right?

Undecidability – Is the language of Turing machines that return Epsilon in their own coding decidable?

Is the language $ { langle M rangle | f ( langle M rangle) = epsilon } $ decidable? $ f () $ means the Turing machine returns $ epsilon $ on your own coding and $ langle M rangle $ stands for the coding (a "string version" of the TM).

I have no idea how to start. How can I decide if I use a reduction, a subroutine technique or the diagonalizability? I would be very happy if you could help me, thank you! 🙂

Reductions – Can current quantum computers determine languages ​​that Turing Machines can not?

I'm just studying Computer Theory at the University, and we've been studying Turing decidability, recognizability, etc. Showing that a problem with Turing machines can not be decided because of reductions has made me think about all the excitement for quantum computers brought.

As such, my question is as follows

Is there a language? L This is not to be decided by a Turing machine, but by a quantum computer?

My guess is NoIn my understanding of Quantum Computers, you can simulate them (albeit more slowly) with a Turing machine. However, my understanding of quantum computing is limited to a 1.5-hour lecture from Microsoft on YouTube, and I would expect that there is much more to the recent developments than I understand

turing machines – Possible number of DFAs, NFAs, DPDAs, NPDAs, NDTMs and DTMs for various input parameters

I came across a problem where I asked for a possible number of DFAs for a given number of states and alphabets. I started guessing if we could find a possible number of different machines for a given number of states, input and stacking alphabets, and so on.

$ Q $ is a lot of states
$ Σ $ is the entered alphabet
$ Γ $ is stack alphabet for PDAs and tape alphabet for TMs
$ L $ means moving to the left in TM head
$ R $ means moving to the right in TM head
$ ε $ is an empty symbol

I came up with the following table:

Enter image description here

First $ Q $ Each cell in the column "Possible number of machines" indicates the possible number of start states. Last $ 2 ^ Q $ is possible combinations of final states. And the remaining middle part is the number of transitions. Combinations. I also used the symbols directly to indicate the number of elements in each group. For example, $ Q $ is a set of states, but I have used $ Q $ Number of states.

Am I correct with these counts?

PS: This is a combinatorial problem in the context of automaton theory.

Linux RedHat + time on machines change after some time configured despite the history service

We have machines in the cluster
One week ago we restart the chronicle service and check the time on all machines

After a chronic restart, time was fine on all machines

After 2 days we noticed that on some machines we have time differences of more than 1 hour

What we see is when we run the chronyd service we see from the output: Can't synchronise: no selectable sources

full details

 systemctl status chronyd
● chronyd.service - NTP client/server
   Loaded: loaded (/usr/lib/systemd/system/chronyd.service; enabled; vendor preset: enabled)
   Active: active (running) since Fri 2019-11-01 19:12:36 UTC; 1 day 15h ago
  Process: 36664 ExecStartPost=/usr/libexec/chrony-helper update-daemon (code=exited, status=0/SUCCESS)
  Process: 36660 ExecStart=/usr/sbin/chronyd $OPTIONS (code=exited, status=0/SUCCESS)
 Main PID: 36663 (chronyd)
   CGroup: /system.slice/chronyd.service
           └─36663 /usr/sbin/chronyd

Nov 02 20:50:01 server_524,sys65.com chronyd(36663): Forward time jump detected!
Nov 02 20:50:01 server_524,sys65.com chronyd(36663): Can't synchronise: no selectable sources
Nov 02 20:53:14 server_524,sys65.com chronyd(36663): Selected source
Nov 02 20:53:14 server_524,sys65.com chronyd(36663): System clock wrong by -6895.552231 seconds, adjustment started
Warning: Journal has been rotated since unit was started. Log output is incomplete or unavailable.

We also performed the following checks, as explained below

However, we have not identified the cause of the change in time
Any suggestion why that might be?

chronyc -n tracking ; date
Reference ID    : (
Stratum         : 7
Ref time (UTC)  : Sun Nov  3 09:23:51 2019
System time     : 2563.336425781 seconds fast of NTP time
Last offset     : +0.000040391 seconds
RMS offset      : 0.000760717 seconds
Frequency       : 30.168 ppm slow
Residual freq   : +0.016 ppm
Skew            : 0.907 ppm
Root delay      : 0.335443 seconds
Root dispersion : 0.427117 seconds
Update interval : 70.4 seconds
Leap status     : Normal
Sun Nov  3 10:07:29 UTC 2019

We compare the time with the time on the machine

date ; hwclock
Sun Nov  3 10:40:18 UTC 2019
Sun 03 Nov 2019 10:45:39 AM UTC  -0.907261 seconds

The configuration of chrony is:

more /etc/chrony.conf
# Use public servers from the pool.ntp.org project.
# Please consider joining the pool (http://www.pool.ntp.org/join.html).
server   iburst

# Ignore stratum in source selection.
stratumweight 0

# Record the rate at which the system clock gains/losses time.
driftfile /var/lib/chrony/drift

# Enable kernel RTC synchronization.

# In first three updates step the system clock instead of slew
# if the adjustment is larger than 10 seconds.
makestep 10 3

# Allow NTP client access from local network.
#allow 192.168/16

# Listen for commands only on localhost.
bindcmdaddress ::1

# Serve time even if not synchronized to any NTP server.
#local stratum 10

keyfile /etc/chrony.keys

# Specify the key used as password for chronyc.
commandkey 1

# Generate command key if missing.

# Disable logging of client accesses.

# Send a message to syslog if a clock adjustment is larger than 0.5 seconds.
logchange 0.5

logdir /var/log/chrony
log measurements statistics tracking

more reason:


 chronyc -n sources
210 Number of sources = 1
MS Name/IP address         Stratum Poll Reach LastRx Last sample
^*                   6   6   377    15  +6522ns(  +94us) +/-  603ms


          Local time: Sun 2019-11-03 11:01:13 UTC

 Universal time: Sun 2019-11-03 11:01:13 UTC
        RTC time: Sun 2019-11-03 11:08:26
       Time zone: Etc/UTC (UTC, +0000)
     NTP enabled: yes
NTP synchronized: no
 RTC in local TZ: yes
      DST active: n/a

Warning: The system is configured to read the RTC time in the local time zone.
         This mode can not be fully supported. It will create various problems
         with time zone changes and daylight saving time adjustments. The RTC
         time is never updated, it relies on external facilities to maintain it.
         If at all possible, use RTC in UTC by calling
         'timedatectl set-local-rtc 0'.


tail -10 measurements.log
2019-11-03 09:20:19     N  6 111 111 1111   6  6 0.00 -8.100e-05  1.460e-04  1.477e-06  3.353e-01  4.268e-01
2019-11-03 09:21:30     N  6 111 111 1111   6  6 0.00 -7.400e-05  1.660e-04  1.477e-06  3.353e-01  4.279e-01
2019-11-03 09:22:40     N  6 111 111 1111   6  6 0.00 -9.400e-05  1.530e-04  1.477e-06  3.353e-01  4.290e-01
2019-11-03 09:23:51     N  6 111 111 1111   6  6 0.00 -3.800e-05  1.810e-04  1.478e-06  3.353e-01  4.300e-01
2019-11-03 09:25:01     N  6 111 111 1111   6  6 0.00 -1.900e-05  2.210e-04  1.477e-06  3.353e-01  4.311e-01
2019-11-03 09:26:11     N  6 111 111 1111   6  6 0.00 -9.500e-05  1.540e-04  1.477e-06  3.353e-01  4.321e-01
2019-11-03 09:27:21     N  6 111 111 1111   6  6 0.00  2.880e-04  9.430e-04  1.480e-06  3.353e-01  4.332e-01
2019-11-03 09:28:33     N  6 111 111 1111   6  6 0.00 -1.420e-04  1.500e-04  1.477e-06  3.353e-01  4.342e-01
2019-11-03 09:29:43     N  6 111 111 1111   6  6 0.00 -9.400e-05  1.340e-04  1.479e-06  3.353e-01  4.353e-01
2019-11-03 09:30:53     N  6 111 111 1111   6  6 0.00 -1.330e-04  2.190e-04  1.479e-06  3.353e-01  4.364e-01


# tail -10 statistics.log
2019-11-03 09:25:01      5.007e-06  4.996e-06  5.989e-06  3.351e-08  3.524e-07 2.2e-02   5   0   5
2019-11-03 09:26:11      2.132e-05  8.896e-05  1.616e-05  4.535e-07  3.464e-06 1.3e+00   6   2   3
2019-11-03 09:27:21      4.463e-05  6.743e-06  4.529e-05  3.689e-07  2.964e-06 2.0e-02   5   0   4
2019-11-03 09:28:33      5.257e-05  1.377e-04  3.979e-05  9.986e-07  9.823e-06 2.3e-01   6   2   4
2019-11-03 09:29:43      4.778e-05  8.748e-05  3.340e-05  1.079e-06  8.638e-06 1.1e-02   5   1   3
   Date (UTC) Time     IP Address    Std dev'n Est offset  Offset sd  Diff freq   Est skew  Stress  Ns  Bs  Nr
2019-11-03 09:30:53      4.487e-05  1.285e-04  4.349e-05  1.598e-06  1.385e-05 6.8e-02   5   1   4
2019-11-03 09:32:03      3.720e-05  8.503e-05  3.075e-05  1.381e-06  2.748e-06 8.3e-03   5   0   5


# tail -10 tracking.log
2019-11-03 09:25:01      7    -30.136      0.386  4.996e-06 N  1  5.989e-06 -2.562e+03
2019-11-03 09:26:11      7    -30.119      0.581  8.896e-05 N  1  1.616e-05 -2.556e+03
2019-11-03 09:27:21      7    -30.081      0.940  6.743e-06 N  1  4.529e-05 -2.550e+03
2019-11-03 09:28:33      7    -30.055      1.338  1.377e-04 N  1  3.979e-05 -2.544e+03
2019-11-03 09:29:43      7    -29.982      2.099  8.748e-05 N  1  3.340e-05 -2.539e+03
   Date (UTC) Time     IP Address   St   Freq ppm   Skew ppm     Offset L Co  Offset sd Rem. corr.
2019-11-03 09:30:53      7    -29.879      3.249  1.285e-04 N  1  4.349e-05 -2.533e+03
2019-11-03 09:32:03      7    -28.764      3.389  8.503e-05 N  1  3.075e-05 -2.527e+03


netstat -plaunt | egrep "chronyd"
udp        0      0 *                           36663/chronyd
udp6       0      0 ::1:323                 :::*                                36663/chronyd

Compiler – Is the assembly language translated to binary? If so, is the assembly language portable across machines?

I tried to find the answer through Google, but I came across contradictory terminology, so I just wanted to be absolutely clear.

Here's my understanding: High-level code written in a high-level language (C, I think, is one of the lowest high-level languages) is translated by the compiler of that language into assembler code.

This assembly code is then translated by something into machine code (also known as binary code or hexadecimal code) (not sure what this translation does).

Does that mean that assembly code, but not machine code, is portable to multiple computers? Or is Assembly not portable, and the only thing that's portable is code written in a higher language?

turing machines – Suppose a program $ P $ with a specific input $ i $ is decidable. Can the same program also be decided with the input of $ F (i) $? Here $ F $ is a calculable function

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virtual machines – Azure Kali Linux VM can not start – NetworkingInternalOperationError

I can not start my Azure Kali Linux VM.
The VM worked yesterday and was shut down yesterday. The Azure console displays it as stopped (enabled). When attempting to start the VM, the error "Provisioning failed. An unexpected error occurred while processing the VM's network profile. Please try again later." NetworkingInternalOperationError "

If I select Stop in the Failed state, the same error will be displayed.

I can not edit network settings or resize settings of the disk because the VM is still in use. Setting the scheduled automatic shutdown will also not work.

What did I miss six hours later? How can I stop and restart the VM properly?

ruby – How is the name of the VirtualBox machine set to match the host name in Vagrantfile for multiple machines?

The following Vagrantfile The configuration does not work because the next VM gets the same name as the previous one. (BTW, not 100% sure, but I think this worked in previous Vagrant versions).

Vagrant.configure(2) do |config|

  config.vm.define "xfcevm" do |xfcevm|
    xfcevm.vm.box = "generic/ubuntu1904"
    xfcevm.vm.hostname = "xfcevm"
    config.vm.provider "virtualbox" do |vb|
      vb.name = "xfcevm"

  config.vm.define "gnomevm" do |gnomevm|
    gnomevm.vm.box = "generic/fedora30"
    gnomevm.vm.hostname = "gnomevm"
    config.vm.provider "virtualbox" do |vb|
      vb.name = "gnomevm"

  config.vm.provider "virtualbox" do |vb|
    # vb.name = config.vm.hostname
    vb.gui = true
    vb.memory = "3072"
    vb.cpus = 1
    vb.customize ("modifyvm", :id, "--vram", "32")

  config.vm.provision "ansible" do |ansible|
    ansible.verbose = "v"
    ansible.compatibility_mode = "2.0"
    ansible.playbook = "setup.yml"

  config.vm.provision "ansible", run: 'always' do |ansible|
    ansible.verbose = "v"
    ansible.compatibility_mode = "2.0"
    ansible.playbook = "tests.yml"


In the queue # vb.name = config.vm.hostname, the assignment returns an object (it is printed with) puts as #) and I do not know enough about Ruby and Vagrant to get a string attribute from it, if that is possible at all.

P.S. A workaround (an alternative to this) would be to retrieve the name of the running VirtualBox machine from the Ansible playbook, as the target stated VBoxManage on this virtual machine as local_action from the Ansible playbook.