KVM Ethernet bridge flaky connection and delay
libvirt 0.9.10 qemu-kvm CentOS 6, STP enabled bridge. One guest has very
unreliable connection. OS is Win Vista, connection shows ip4 Internet
connected but often 100% packet loss pinging gateway. I run tcpdump on
host when pinging gateway from guest and I dont see the icmp requests
until seconds after the ping timeout. Guest uses br0
bridge name bridge id STP enabled interfaces
br0 8000.90b11c106fec yes em1
vnet0
vnet1
virbr0 8000.525400b7455a yes virbr0-nic
Thursday, 3 October 2013
Wednesday, 2 October 2013
Euler character of etale finite cover
Euler character of etale finite cover
Let $\pi: \tilde{X} \to X$ be an etale finite cover, then why the Euler
character has relation:
$$\chi(\tilde{X},\mathcal{O}_{\tilde{X}})=\deg(\pi)\chi({X},\mathcal{O}_{{X}}).$$
I try to use Riemann-Roch, but do not know how to relate Chern characters
and Todd class of them.
Besides, I found a similar question on topological setting.
Let $\pi: \tilde{X} \to X$ be an etale finite cover, then why the Euler
character has relation:
$$\chi(\tilde{X},\mathcal{O}_{\tilde{X}})=\deg(\pi)\chi({X},\mathcal{O}_{{X}}).$$
I try to use Riemann-Roch, but do not know how to relate Chern characters
and Todd class of them.
Besides, I found a similar question on topological setting.
Intersect not giving expected results
Intersect not giving expected results
In the below code if I iterated over L3 I would expect to have 2 results
available. However it only has one result and that result is the objTest
with a Id = 9. I thought it should be a result set with two objtest s' Id
= 9 and Id = 10.
class Program
{
public class objTest
{
public int Value { get; set; }
public bool On { get; set; }
public int Id { get; set; }
}
class PramComp : EqualityComparer<objTest>
{
public override bool Equals(objTest x, objTest y)
{
return x.Value == y.Value;
}
public override int GetHashCode(objTest obj)
{
return obj.Value.GetHashCode();
}
}
static void Main(string[] args)
{
List<objTest> L1 = new List<objTest>();
L1.Add(new objTest { Value = 1, On = true ,Id =1});
L1.Add(new objTest { Value = 2, On = false ,Id =2});
L1.Add(new objTest { Value = 3, On = false, Id = 3 });
L1.Add(new objTest { Value = 4, On = false ,Id =4});
L1.Add(new objTest { Value = 5, On = false ,Id =5});
List<objTest> L2 = new List<objTest>();
L2.Add(new objTest { Value = 6, On = false ,Id =6});
L2.Add(new objTest { Value = 7, On = false ,Id=7});
L2.Add(new objTest { Value = 8, On = false,Id =8 });
L2.Add(new objTest { Value = 1, On = true,Id =9 });
L2.Add(new objTest { Value = 1, On = true, Id =10 });
var L3 = L2.Intersect(L1, new PramComp());
}
}
So I have made a mistake with my code if I want to return the two results
Id=9 and Id=10. Could someone tell me where my mistake is?
In the below code if I iterated over L3 I would expect to have 2 results
available. However it only has one result and that result is the objTest
with a Id = 9. I thought it should be a result set with two objtest s' Id
= 9 and Id = 10.
class Program
{
public class objTest
{
public int Value { get; set; }
public bool On { get; set; }
public int Id { get; set; }
}
class PramComp : EqualityComparer<objTest>
{
public override bool Equals(objTest x, objTest y)
{
return x.Value == y.Value;
}
public override int GetHashCode(objTest obj)
{
return obj.Value.GetHashCode();
}
}
static void Main(string[] args)
{
List<objTest> L1 = new List<objTest>();
L1.Add(new objTest { Value = 1, On = true ,Id =1});
L1.Add(new objTest { Value = 2, On = false ,Id =2});
L1.Add(new objTest { Value = 3, On = false, Id = 3 });
L1.Add(new objTest { Value = 4, On = false ,Id =4});
L1.Add(new objTest { Value = 5, On = false ,Id =5});
List<objTest> L2 = new List<objTest>();
L2.Add(new objTest { Value = 6, On = false ,Id =6});
L2.Add(new objTest { Value = 7, On = false ,Id=7});
L2.Add(new objTest { Value = 8, On = false,Id =8 });
L2.Add(new objTest { Value = 1, On = true,Id =9 });
L2.Add(new objTest { Value = 1, On = true, Id =10 });
var L3 = L2.Intersect(L1, new PramComp());
}
}
So I have made a mistake with my code if I want to return the two results
Id=9 and Id=10. Could someone tell me where my mistake is?
Why System.currentTimeMillis() generate incorrect long value?
Why System.currentTimeMillis() generate incorrect long value?
It was discussed too many times, I know, but I can't get why the
milliseconds generated by mine:
System.currentTimeMillis();
Or by:
Calendar.getInstance(TimeZone.getTimeZone("UTC")).getTimeInMillis()
Are not equal to what I see on http://www.epochconverter.com/?
What I need is to merely generate a String of concrete format, but I've
found out the milliseconds aren't right.
Just in case here is how I do it:
private static final String DATE_PATTERN = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'";
public static String getCurrentTimestamp() {
long time = System.currentTimeMillis();
SimpleDateFormat sdf = new SimpleDateFormat(DATE_PATTERN);
String lastModifiedTime = sdf.format(time);
Logger.logVerbose(TAG, "Generated timestamp is " + lastModifiedTime);
return lastModifiedTime;
}
What I finally get is just a local time, but I need the only time which is
pure UTC without conjunction with my timezone.
I've even checked it with SQLite (using the SELECT
strftime('%s',timestring);) and got the correct milliseconds. Why then I
got it incorrectly generated by those two statements I posted above?
Thanks a lot in advance.
It was discussed too many times, I know, but I can't get why the
milliseconds generated by mine:
System.currentTimeMillis();
Or by:
Calendar.getInstance(TimeZone.getTimeZone("UTC")).getTimeInMillis()
Are not equal to what I see on http://www.epochconverter.com/?
What I need is to merely generate a String of concrete format, but I've
found out the milliseconds aren't right.
Just in case here is how I do it:
private static final String DATE_PATTERN = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'";
public static String getCurrentTimestamp() {
long time = System.currentTimeMillis();
SimpleDateFormat sdf = new SimpleDateFormat(DATE_PATTERN);
String lastModifiedTime = sdf.format(time);
Logger.logVerbose(TAG, "Generated timestamp is " + lastModifiedTime);
return lastModifiedTime;
}
What I finally get is just a local time, but I need the only time which is
pure UTC without conjunction with my timezone.
I've even checked it with SQLite (using the SELECT
strftime('%s',timestring);) and got the correct milliseconds. Why then I
got it incorrectly generated by those two statements I posted above?
Thanks a lot in advance.
WCF WebFaultException ExceptionDetail
WCF WebFaultException ExceptionDetail
I'm creating a WCF service that returns data in JSON Format. I'm trying to
figure out how to best handle exceptions and I'm trying to use the
WebFaultException class to return an exception detail message in the
response, which can later be outputted to the user.
A simple Test of this method I am trying is as follows
The WCF Service method
<WebInvoke(Method:="POST",
ResponseFormat:=WebMessageFormat.Json)>
<OperationContract()>
Public Function Test() As Object
Throw New WebFaultException(Of String)("Message Details",
Net.HttpStatusCode.NotFound)
End Function
From what I found searching for answers to this questions, you should give
the service a behaviorconfiguartion which sets
includeExceptionDetailInFaults to true.
My Web.Config
<service name="WebserviceExceptionTest.Service"
behaviorConfiguration="behavior">
<endpoint address=""
behaviorConfiguration="WebserviceExceptionTest.ServiceAspNetAjaxBehavior"
binding="webHttpBinding"
contract="WebserviceExceptionTest.Service" />
</service>
<serviceBehaviors>
<behavior name="behavior">
<serviceDebug includeExceptionDetailInFaults="True"/>
</behavior>
Unfortunately, this appears to not do the trick for me and the response
still does not include the exception detail, the JSON string looks like
this:
{"ExceptionDetail":null,"ExceptionType":null,"Message":"Not
Found","StackTrace":null}
Does anyone have any idea of what it is I am doing wrong, or am I just
entirely on the wrong path? Thanks!
I'm creating a WCF service that returns data in JSON Format. I'm trying to
figure out how to best handle exceptions and I'm trying to use the
WebFaultException class to return an exception detail message in the
response, which can later be outputted to the user.
A simple Test of this method I am trying is as follows
The WCF Service method
<WebInvoke(Method:="POST",
ResponseFormat:=WebMessageFormat.Json)>
<OperationContract()>
Public Function Test() As Object
Throw New WebFaultException(Of String)("Message Details",
Net.HttpStatusCode.NotFound)
End Function
From what I found searching for answers to this questions, you should give
the service a behaviorconfiguartion which sets
includeExceptionDetailInFaults to true.
My Web.Config
<service name="WebserviceExceptionTest.Service"
behaviorConfiguration="behavior">
<endpoint address=""
behaviorConfiguration="WebserviceExceptionTest.ServiceAspNetAjaxBehavior"
binding="webHttpBinding"
contract="WebserviceExceptionTest.Service" />
</service>
<serviceBehaviors>
<behavior name="behavior">
<serviceDebug includeExceptionDetailInFaults="True"/>
</behavior>
Unfortunately, this appears to not do the trick for me and the response
still does not include the exception detail, the JSON string looks like
this:
{"ExceptionDetail":null,"ExceptionType":null,"Message":"Not
Found","StackTrace":null}
Does anyone have any idea of what it is I am doing wrong, or am I just
entirely on the wrong path? Thanks!
Tuesday, 1 October 2013
Naive Bayes and Logistic Regression Error Rate
Naive Bayes and Logistic Regression Error Rate
I have been trying to figure out the correlation between the error rate
and the number of features in both of these models. I watched some videos,
and the creator of the video said that a simple model can be better than a
complicated model. So I figured that the more features I had the greater
the error rate would be. This did not prove to be true in my work, and
when I had less features the error rate went up. I'm not sure if I'm doing
this incorrectly, or if the guy in the video made a mistake. Can someone
care to explain? I also am curious how features relate to Logistic
Regression's error rate as well.
I have been trying to figure out the correlation between the error rate
and the number of features in both of these models. I watched some videos,
and the creator of the video said that a simple model can be better than a
complicated model. So I figured that the more features I had the greater
the error rate would be. This did not prove to be true in my work, and
when I had less features the error rate went up. I'm not sure if I'm doing
this incorrectly, or if the guy in the video made a mistake. Can someone
care to explain? I also am curious how features relate to Logistic
Regression's error rate as well.
jQuery round number to 2 decimal places
jQuery round number to 2 decimal places
I have a little problem that I can't seem to get my head round...
I have figure that I need to find what the VAT element of it would be, I
have the following jQuery which works but it doesn't fix it to 2 decimal
places.
var ThreeMonthPriceFinal = "99.29";
var ThreeMonthPriceVAT = ThreeMonthPriceFinal * 0.2.toFixed(2);
alert(ThreeMonthPriceVAT);
It works out the VAT correctly but adds lots of recurring digits that i
don't need... I can't round it up as with VAT you not really supposed to.
http://jsfiddle.net/Xg4Qs/
The Jfiddle shows £19.858000000000004 I need this to show 19.86, i've
tried the following but it rounds it up to the whole amount not just 1p.
var ThreeMonthPriceVAT = Math.round(ThreeMonthPriceFinal * 0.2).toFixed(2);
Can anyone help me?
I have a little problem that I can't seem to get my head round...
I have figure that I need to find what the VAT element of it would be, I
have the following jQuery which works but it doesn't fix it to 2 decimal
places.
var ThreeMonthPriceFinal = "99.29";
var ThreeMonthPriceVAT = ThreeMonthPriceFinal * 0.2.toFixed(2);
alert(ThreeMonthPriceVAT);
It works out the VAT correctly but adds lots of recurring digits that i
don't need... I can't round it up as with VAT you not really supposed to.
http://jsfiddle.net/Xg4Qs/
The Jfiddle shows £19.858000000000004 I need this to show 19.86, i've
tried the following but it rounds it up to the whole amount not just 1p.
var ThreeMonthPriceVAT = Math.round(ThreeMonthPriceFinal * 0.2).toFixed(2);
Can anyone help me?
Can abstract nonsense be helpful here?
Can abstract nonsense be helpful here?
Here a question for those among you, who teach homotopics/Algebraic
Topology at University. I encountered some questions that were quite easy
to solve in category hTop instead of Top (example 1, example 2). In my
answers I said that familiarity with categories was necessary to
understand. Can answers like that really be helpful to the student? If not
then I should stop with it. The student must be central in my thinking
when I answer a question. It must be not be a way just to expose my
knowledge (my flesh is weak).
You know the best what is helpful for your students. So I ask you.
Here a question for those among you, who teach homotopics/Algebraic
Topology at University. I encountered some questions that were quite easy
to solve in category hTop instead of Top (example 1, example 2). In my
answers I said that familiarity with categories was necessary to
understand. Can answers like that really be helpful to the student? If not
then I should stop with it. The student must be central in my thinking
when I answer a question. It must be not be a way just to expose my
knowledge (my flesh is weak).
You know the best what is helpful for your students. So I ask you.
what is the best way to keep updated more than 75 windows servers?
what is the best way to keep updated more than 75 windows servers?
After virtualising our server infraestructure, in the last two years the
number of windows servers has grown from aprox. 20 to 75, mainly by
migrating every service of our corporation to his own vm, but we also are
deploying new applications that require one or more servers.
In the old times, keeping windows updated take me only 1 hour to do this
(boring) task, but now it's coming really time-consuming and also
error-prone (too many servers ,some of them are clusters or nbl, and
others have services that depends in other servers, that expect the other
server is online when it's restarted, so you can't reboot all at one
time).
Our workflow is the following:
1- Someone aproves in WSUS the updates of the month after little testing.
2- One time every month, on Friday evening, when almost isn't anyone
working, I start the boring task of log in every server, wuauclt
/detectnow, click to download updates, click to install, reboot (keeping
in mind what other servers are rebooting at the moment), log in again,
check if is any pending update after reboot, etc etc.
I searched in internet and I didn't find anything that can help me in this
task, I tried to make a c# app that manage all of this without manually
login every server, but wuapi.dll is unable to download/install in remote.
So, I think this has to be a common problem, what other people do? As you
can expect, we can't leave updates to install automatically or reboot when
automatic updates want.
After virtualising our server infraestructure, in the last two years the
number of windows servers has grown from aprox. 20 to 75, mainly by
migrating every service of our corporation to his own vm, but we also are
deploying new applications that require one or more servers.
In the old times, keeping windows updated take me only 1 hour to do this
(boring) task, but now it's coming really time-consuming and also
error-prone (too many servers ,some of them are clusters or nbl, and
others have services that depends in other servers, that expect the other
server is online when it's restarted, so you can't reboot all at one
time).
Our workflow is the following:
1- Someone aproves in WSUS the updates of the month after little testing.
2- One time every month, on Friday evening, when almost isn't anyone
working, I start the boring task of log in every server, wuauclt
/detectnow, click to download updates, click to install, reboot (keeping
in mind what other servers are rebooting at the moment), log in again,
check if is any pending update after reboot, etc etc.
I searched in internet and I didn't find anything that can help me in this
task, I tried to make a c# app that manage all of this without manually
login every server, but wuapi.dll is unable to download/install in remote.
So, I think this has to be a common problem, what other people do? As you
can expect, we can't leave updates to install automatically or reboot when
automatic updates want.
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