老师好：我有点不太明白SMO算法中，选择第一个变量的时候说的违反KKT条件，这个KKT条件是怎么来的？

我知道原始SVM问题是一个二次优化问题，通过KKT条件来求解，优化空间从w与b变换到了α空间进行优化，此时仍然带着原始问题的KKT条件。接着对α的求解我们采用SMO算法，虽然SMO的求解思路是大二次优化问题花间为多个二元的小二次优化问题，但是求解的思路是直接对二元目标函数直接求导来寻找最优解，并通过约束条件对求导找到的最优解进行剪裁，来得到满足约束条件的最优解。

但是对于优化参数选择中第一个参数的选择上，说找到第一个违反KKT条件的参数α，这里所说的KKT条件是怎么一会事？是指SMO算法所要求解的目标函数的KKT条件吗？如果是这样，在视频中并未提及这个KKT是怎么来的，只是直接给出，我自己试着退了一下，并未得到对应结果，所以想请教老师，在SMO算法选择第一个参数α，所说的KKT条件是怎么来的？

老师，我不明白为什么title的类型为字符串呢，其他的都为对象。

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老师，我这边接口serviceapi，provider01，provider02 都启动正常

2020-07-07 17:04:11.963 ERROR 15980 --- [nfoReplicator-0] c.n.d.s.t.d.RedirectingEurekaHttpClient  : Request execution error. endpoint=DefaultEndpoint{ serviceUrl='http://localhost:8085/eureka/}

com.sun.jersey.api.client.ClientHandlerException: java.net.ConnectException: Connection refused: connect

at com.sun.jersey.client.apache4.ApacheHttpClient4Handler.handle(ApacheHttpClient4Handler.java:187) ~[jersey-apache-client4-1.19.1.jar:1.19.1]

at com.sun.jersey.api.client.filter.GZIPContentEncodingFilter.handle(GZIPContentEncodingFilter.java:123) ~[jersey-client-1.19.1.jar:1.19.1]

at com.netflix.discovery.EurekaIdentityHeaderFilter.handle(EurekaIdentityHeaderFilter.java:27) ~[eureka-client-1.9.13.jar:1.9.13]

at com.sun.jersey.api.client.Client.handle(Client.java:652) ~[jersey-client-1.19.1.jar:1.19.1]

at com.sun.jersey.api.client.WebResource.handle(WebResource.java:682) ~[jersey-client-1.19.1.jar:1.19.1]

at com.sun.jersey.api.client.WebResource.access$200(WebResource.java:74) ~[jersey-client-1.19.1.jar:1.19.1]

at com.sun.jersey.api.client.WebResource$Builder.post(WebResource.java:570) ~[jersey-client-1.19.1.jar:1.19.1]

at com.netflix.discovery.shared.transport.jersey.AbstractJerseyEurekaHttpClient.register(AbstractJerseyEurekaHttpClient.java:56) ~[eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$1.execute(EurekaHttpClientDecorator.java:59) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.MetricsCollectingEurekaHttpClient.execute(MetricsCollectingEurekaHttpClient.java:73) ~[eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$1.execute(EurekaHttpClientDecorator.java:59) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.RedirectingEurekaHttpClient.executeOnNewServer(RedirectingEurekaHttpClient.java:118) ~[eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.RedirectingEurekaHttpClient.execute(RedirectingEurekaHttpClient.java:79) ~[eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$1.execute(EurekaHttpClientDecorator.java:59) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.RetryableEurekaHttpClient.execute(RetryableEurekaHttpClient.java:120) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$1.execute(EurekaHttpClientDecorator.java:59) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.SessionedEurekaHttpClient.execute(SessionedEurekaHttpClient.java:77) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.DiscoveryClient.register(DiscoveryClient.java:847) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.InstanceInfoReplicator.run(InstanceInfoReplicator.java:121) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.InstanceInfoReplicator$1.run(InstanceInfoReplicator.java:101) [eureka-client-1.9.13.jar:1.9.13]

at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [na:1.8.0_231]

at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_231]

at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180) [na:1.8.0_231]

at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) [na:1.8.0_231]

at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_231]

at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_231]

at java.lang.Thread.run(Thread.java:748) [na:1.8.0_231]

Caused by: java.net.ConnectException: Connection refused: connect

at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method) ~[na:1.8.0_231]

at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:85) ~[na:1.8.0_231]

at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) ~[na:1.8.0_231]

at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) ~[na:1.8.0_231]

at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) ~[na:1.8.0_231]

at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172) ~[na:1.8.0_231]

at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[na:1.8.0_231]

at java.net.Socket.connect(Socket.java:606) ~[na:1.8.0_231]

at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:121) ~[httpclient-4.5.10.jar:4.5.10]

at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:180) ~[httpclient-4.5.10.jar:4.5.10]

at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:144) ~[httpclient-4.5.10.jar:4.5.10]

at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:134) ~[httpclient-4.5.10.jar:4.5.10]

at org.apache.http.impl.client.DefaultRequestDirector.tryConnect(DefaultRequestDirector.java:605) ~[httpclient-4.5.10.jar:4.5.10]

at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:440) ~[httpclient-4.5.10.jar:4.5.10]

at org.apache.http.impl.client.AbstractHttpClient.doExecute(AbstractHttpClient.java:835) ~[httpclient-4.5.10.jar:4.5.10]

at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:118) ~[httpclient-4.5.10.jar:4.5.10]

at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:56) ~[httpclient-4.5.10.jar:4.5.10]

at com.sun.jersey.client.apache4.ApacheHttpClient4Handler.handle(ApacheHttpClient4Handler.java:173) ~[jersey-apache-client4-1.19.1.jar:1.19.1]

... 30 common frames omitted

2020-07-07 17:04:11.964  WARN 15980 --- [nfoReplicator-0] c.n.d.s.t.d.RetryableEurekaHttpClient    : Request execution failed with message: java.net.ConnectException: Connection refused: connect

2020-07-07 17:04:11.967  WARN 15980 --- [nfoReplicator-0] com.netflix.discovery.DiscoveryClient    : DiscoveryClient_CONSUMER-FEIGN/DESKTOP-8NIQN7P:consumer-feign:8083 - registration failed Cannot execute request on any known server

com.netflix.discovery.shared.transport.TransportException: Cannot execute request on any known server

at com.netflix.discovery.shared.transport.decorator.RetryableEurekaHttpClient.execute(RetryableEurekaHttpClient.java:112) ~[eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) ~[eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$1.execute(EurekaHttpClientDecorator.java:59) ~[eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.SessionedEurekaHttpClient.execute(SessionedEurekaHttpClient.java:77) ~[eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) ~[eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.DiscoveryClient.register(DiscoveryClient.java:847) ~[eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.InstanceInfoReplicator.run(InstanceInfoReplicator.java:121) [eureka-client-1.9.13.jar:1.9.13]

at com.netflix.discovery.InstanceInfoReplicator$1.run(InstanceInfoReplicator.java:101) [eureka-client-1.9.13.jar:1.9.13]

at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [na:1.8.0_231]

at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_231]

at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180) [na:1.8.0_231]

at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) [na:1.8.0_231]

at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_231]

at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_231]

at java.lang.Thread.run(Thread.java:748) [na:1.8.0_231]

问题：例题中，第三行：new ChildClass().f();，f()方法并不属于ChildClass()，为什么ChildClass()能调用f()方法。

引用课上使用递归求 n!代码中的一句：

“   System.out.printf("%d 阶乘的结果:%s%n", 10, factorial(10));   ”

请问这里的 %d  %s 是什么意思？怎么使用？属于那一块儿的知识？课上怎么没讲这一块？

老师这边还是有一点不怎么理解，黄色部分为什么要这样写

老师的讲的意思是9行和10行都对吗？大纲上给的是第9行那样写，老师写的是第10行那种

分享，处理python smtplib.SMTPAuthenticationError: (535, b'Error: authentication failed')这种报错的方法：

老师，这节课中说到的VFSTPD章节在哪，前面没讲过啊，还有ftp服务器也没讲过，感觉缺了好多课啊

视屏中老师提到，图像处理问题一般用深度学习，非图像问题一般使用xgboost，机器学习这一章节，我们学了随机森林，gbdt，adaboost，xgboost这几种基于决策树的集成算法，如果xgboost是最常用的，是否它就是全能的，只要是非图像问题都优先选择xgboost？其他几种方法又在哪种场景下适合用呢？在实际的应用中，我们应该如何来选择算法？（当然我目前没有任何经验，无法靠经验选择）

老师，我两个问题想问一下：

1. 响应内容在浏览器上面显示不完全是怎么回事，如下图所示：

   这个我编写的响应内容是"账号都不记得有什么用"，却只显示一部分

   

   这个我编写的响应内容是"欢迎来到德莱联盟！！！"，最后三个叹号没出来

   

   我一开始觉得是编写响应内容的方法出了问题，检查了没发现问题：

   

   看了一下LoginServlet类，也没问题：

   

   最后看了一下推送类，也没问题：

   

2. 请问响应内容和响应头都是以同样的方式推送到客户机浏览器的（如下图95，96行），为什么响应内容可以显示在浏览器，响应头却没显示出来，这是为什么呢？

   
   

   
   

>>> a="zzy喜欢{运动}不喜欢{工作}正在学{编程}"
>>> a
'zzy喜欢{运动}不喜欢{工作}正在学{编程}'
>>> a.format(运动="a",工作="b",编程="c")
'zzy喜欢a不喜欢b正在学c'

这怎么就可以了呢？

为什么我这两行代码和老师的不一样,还能运行

>>> a="zzy喜欢{a}不喜欢{b}正在学{c}"
>>> a
'zzy喜欢{a}不喜欢{b}正在学{c}'
>>> a.format(a="足球"，b="工作"，c="编程")
SyntaxError: invalid character in identifier   

为什么会报错啊？{}里不可以是“a”吗？

老师，这边的None是指什么呢，是因为结果已经运行了一次不能再打印了吗