internals

问题 I am using a std::deque for storing a large collection of items. I know that deques is implemented as a list of vectors. The size of those vectors cannot be set but I wander what is the algorithm for choosing that size. 回答1: deque is implemented as a vector of vectors (a list of vectors would impede the constant time random access). The size of the secondary vectors is implementation dependent, a common algorithm is to use a constant size in bytes. 回答2: My deque implementation, the one from

问题 This is a puzzler! :D Is there a way to force Hibernate to load a collection for an entity without loading the entire entity first? Let m explain better. I have a Role entity annotated this way: @Entity(name="Role") @Table(name = "ROLES") @Inheritance(strategy = InheritanceType.TABLE_PER_CLASS) @javax.persistence.TableGenerator( name="GENERATED_IDS", table="GENERATED_IDS", valueColumnName = "ID" ) public abstract class Role implements Serializable { private static final long serialVersionUID

问题 In sum: I need to write a List Comprehension in which i refer to list that is being created by the List Comprehension. This might not be something you need to do every day, but i don't think it's unusual either. Maybe there's no answer here--still, please don't tell me i ought to use a for loop. That might be correct, but it's not helpful. The reason is the problem domain: this line of code is part of an ETL module, so performance is relevant, and so is the need to avoid creating a temporary

问题 I recently got thinking about alignment... It's something that we don't ordinarily have to consider, but I've realized that some processors require objects to be aligned along 4-byte boundaries. What exactly does this mean, and which specific systems have alignment requirements? Suppose I have an arbitrary pointer: unsigned char* ptr Now, I'm trying to retrieve a double value from a memory location: double d = **((double*)ptr); Is this going to cause problems? 回答1: It can definitely cause

问题 I recently got thinking about alignment... It's something that we don't ordinarily have to consider, but I've realized that some processors require objects to be aligned along 4-byte boundaries. What exactly does this mean, and which specific systems have alignment requirements? Suppose I have an arbitrary pointer: unsigned char* ptr Now, I'm trying to retrieve a double value from a memory location: double d = **((double*)ptr); Is this going to cause problems? 回答1: It can definitely cause

问题 I'm certainly missing some fundamental point about the injector, but I fail to understand why exactly this angular.module('app').config(function ($provide) { ... }); and this angular.module('app').config(function ($injector) { $injector.invoke(function ($provide) { ... }); }); work as intended, while this app.run(function($provide) { ... }); will throw Error: [$injector:unpr] Unknown provider: $provideProvider <- $provide As follows from the above, config has some special relationship with

问题 In a previous question yesterday, in comments, I came to know that in python __code__ atrribute of a function is mutable. Hence I can write code as following def foo(): print "Hello" def foo2(): print "Hello 2" foo() foo.__code__ = foo2.__code__ foo() Output Hello Hello 2 I tried googling, but either because there is no information(I highly doubt this), or the keyword ( __code__ ) is not easily searchable, I couldn't find a use case for this. It doesn't seem like "because most things in

问题 In a previous question yesterday, in comments, I came to know that in python __code__ atrribute of a function is mutable. Hence I can write code as following def foo(): print "Hello" def foo2(): print "Hello 2" foo() foo.__code__ = foo2.__code__ foo() Output Hello Hello 2 I tried googling, but either because there is no information(I highly doubt this), or the keyword ( __code__ ) is not easily searchable, I couldn't find a use case for this. It doesn't seem like "because most things in

问题 Context This is a question mainly about Lucene (or possibly Solr) internals. The main topic is faceted search , in which search can happen along multiple independent dimensions (facets) of objects (for example size, speed, price of a car). When implemented with relational database, for a large number of facets multi-field indices are not useful, since facets can be searched in any order, so a specific ordered multi-index is used with low chance, and creating all possible orderings of indices

问题 Context This is a question mainly about Lucene (or possibly Solr) internals. The main topic is faceted search , in which search can happen along multiple independent dimensions (facets) of objects (for example size, speed, price of a car). When implemented with relational database, for a large number of facets multi-field indices are not useful, since facets can be searched in any order, so a specific ordered multi-index is used with low chance, and creating all possible orderings of indices