Question

我有一个已排序元素的列表。与最后的元素相比，第一元素应该被优先化。目前，我只是使用org.springframework.transaction.TransactionSystemException: Could not commit JPA transaction; nested exception is javax.persistence.RollbackException: Transaction marked as rollbackOnly at org.springframework.orm.jpa.JpaTransactionManager.doCommit(JpaTransactionManager.java:526) at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:761) at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:730) at org.springframework.test.context.transaction.TransactionContext.endTransaction(TransactionContext.java:128) at org.springframework.test.context.transaction.TransactionalTestExecutionListener.afterTestMethod(TransactionalTestExecutionListener.java:224) at org.springframework.test.context.TestContextManager.afterTestMethod(TestContextManager.java:313) at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:94) at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84) at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325) at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:254) at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:89) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268) at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61) at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70) at org.junit.runners.ParentRunner.run(ParentRunner.java:363) at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:193) at org.junit.runner.JUnitCore.run(JUnitCore.java:137) at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:119) at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:42) at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:234) at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:74) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:483) at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144) Caused by: javax.persistence.RollbackException: Transaction marked as rollbackOnly at org.hibernate.jpa.internal.TransactionImpl.commit(TransactionImpl.java:74) at org.springframework.orm.jpa.JpaTransactionManager.doCommit(JpaTransactionManager.java:517) ... 29 more 2016-03-26 20:53:52.913 INFO 2448 --- [ Thread-3] s.c.a.AnnotationConfigApplicationContext : Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@20deea7f: startup date [Sat Mar 26 20:53:44 CET 2016]; root of context hierarchy 2016-03-26 20:53:52.924 INFO 2448 --- [ Thread-3] j.LocalContainerEntityManagerFactoryBean : Closing JPA EntityManagerFactory for persistence unit 'default'从我的列表中选择项目。

我正在编写的算法在使用不同的概率分布时效率会更高（如上所述）。不幸的是，我不确定如何实现它

Answer 1

您可以使用geometric distribution。在几何分布中，获得较大数字的概率呈指数下降。您可以通过调整一些参数来调整优先级。

import numpy
pr = 0.5
x = numpy.random.geometric(pr, 1)[0]

在上面的代码段中，x将对应于您在第一次成功之前必须执行的伯努利试验次数，其中成功概率为0.5。

通常，分布将返回某个数字n的概率等于（1-pr）^（n-1）* pr，其中pr是参数，如代码所示。

所以现在你应该使用x-1（因为列表是0索引的并且x＆gt; = 1）作为选择列表中元素的索引，因为较小的值具有更高的概率从分发中出现，我们已成功捕获您的要求：）

优先列出列表中的第一项（随机和概率分布）

1 个答案: