莫叶何竹

背景

随着AIGC概念及diffusion model在视觉领域的发光发热。OpenAI结合CLIP与diffusion model提出了一个二阶段的文本生成图片范式Dalle2¹，能够更精细的从语义层面控制图片的生成效果。得益于其训练范式，Dalle2的图片生成的质量不弱于GLIDE²,但生成器的多样性有明显提升。下面我们来看它是怎么做的吧！

1 从直觉上理解DDPM

在详细推到公式之前，我们先从直觉上理解一下什么是扩散

对于常规的生成模型，如GAN，VAE，它直接从噪声数据生成图像，我们不妨记噪声数据为$z$,其生成的图片为$x$

1 问题引出

1.1 从最近邻搜索谈起(nearest neighbor search, NN)

最近邻检索：给定一张查询图片q(即query)（或文本），从数据库$\mathcal{X}$中找到与之最相近的N张图片（或文本）。在实际的检索场景中，我们会用一条向量来作为图片(或文本)的表征。

Welcome to Hexo! This is your very first post. Check documentation for more info. If you get any problems when using Hexo, you can find the answer in troubleshooting or you can ask me on GitHub.

Quick Start

Create a new post

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$ hexo new "My New Post"

More info: Writing

Run server

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$ hexo server

More info: Server

Generate static files

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$ hexo generate

More info: Generating

Deploy to remote sites

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$ hexo deploy

More info: Deployment

Setup

To Update NPM: npm install npm@latest -g.

In 2015 it makes sense to use NVM. NVM Installation Instructions.

Update NPM: npm install npm@latest -g

Hexo: why can't you use helper functions in source code? This should be in docs.

Creating a Custom Index File in Hexo

Trying to generate a custom index file in source, hexo would ignore source/index.md no matter what I did. What I had to do was uninstall hexo-generator-index. See here. Then it works. So, that will be part of the setup for my theme. But, it's worth it in order to properly seperate the theme from the content, I think. Having everyone edit the theme index.ejs template is no good.

Hexo Rendering Raw EJS File Problem I Encountered

Sometimes the server would keep rendering an old version of my code, but as text. So I'd see stuff like

<% if (site.tags.length){ %>

The raw ejs, essentially. Restarting the server or running hexo clean didn't do anything.

After some time, I realized it was due to the gedit swap files being read by hexo as the actual layout files: for example, tag.ejs~. My partial helpers looked like: <%- partial('_partials/tag') %>, and apparently hexo was reading in tag.ejs~ instead of tag.ejs. And therefore, the ejs wasn't rendering.

To fix this, I simply changed my partial helper to <%- partial('_partials/tag.ejs') %>. Problem solved.

Hexo Excerpt Variable

I was confused by the behavior of the hexo excerpt variable. If you define excerpt: something in the front matter, hexo ignores that. Instead, to get it to work, one needs to add a <!-- more --> comment in the source of the post. Or, you can install a plugin that allows you to define custom excerpt in the front matter.

Scripts Directory

One of the things I really discovered too late is the "Scripts" directory in the theme folder. In Hexo, the various plugins drive the structure of the site, as opposed to the placement of different files and directories, as in Jekyll. The plugins programatically create folder structure, etc, where in Jekyll I mostly used the liquid markup to structure the site.

The problem is, then, that the user wants to extend hexo to do some sort of custom thing. If one had to publish a new plugin, that'd be too much work. But the theme level scripts folder allows one to extend the base hexo functionality in 'user space' effectively.

Top tech talent knows that industry recruiters often bring a stack of pre-negotiated offers to university infosessions, so that they can snag programmers and UX designers who really stand out. Instead of spending valuable time validating a particularly promising candidate's skillset through a protracted series of interviews, it's often more efficient to simply give the individual an offer right then and there. Internal studies at Google have shown that experienced recruiters can usually tell if a programmer has 'what it takes' just from how they act at infosessions: the insightful questions they ask, the stickers on their laptop, and how they comport themselves in general.

Here are some of the resources I found helpful for learning to develop Dynamics NAV web service based applications.

C/AL Programming:

Introduction to CAL Programming This provides a good overview of the basics of CAL programming, which can become necessary in building a web service applications when a custom codeunit or page extension is required.

Setting up Web Services:

Vjecko Web Service Recorded Session Vjecko.com has a lot of detailed articles about web service programming, but this older post has a pdf and recorded session that shows how to expose and connect to web services from a .NET application. Unfortunately, he shows how to create Web Service references in .NET using the now-deprecated Web Refrence method (from .NET 2) instead of the more current Service Reference method.

Using Service Reference to Connect to Web Services This explains how to use Service Reference, using code instead of XML web.config configuration, which I found difficult to configure. (Each time I updated the service reference, I would have to reconfigure the XML).

NAV Upgrade Process:

Migration to SQL Server from C/SIDE Database In order to use web services, you don't need to be using the Role Tailored Client, but you must be using the a SQL server based NAV database. Web Services can be configured and exposed using the Classic Client for SQL Server Databases.

Debugging Code Called by Web Services C/AL code won't necessarily execute the same as it did in the Classic Client when called as a Web Service. C/AL code called as web service execute in the NAV Server tier, instead of the client. Certain functions aren't available for code running in the NAV Server, and some design changes need to be made (for example, CONFIRM dialogue boxes don't make sense in the context of a web service). To debug the codeunits called through web services (or the Role Tailored Client), you will need to use Visual Studio. More information.

Deploying a .NET Application:

Deploying to IIS After you've built a .NET application that consumes .NET web services, you'll have to find a way to deploy it on your servers, or Azure. Connection strings can be used to specify different NAV servers for different environments (like development, QA, and prod).

One of the problems I faced in building a non-trivial application that consumed NAV Web Services was figuring out how to "join" fields from different tables. For example, when exposing a list of jobs from a job table which includes a resource needed for the job, you might need more than just the resource id that's a field in the table: you might also need the resource name and description. While this is easy to get for one record, what about when you need a few hundred records in a table that has been dynamically filtered? When exposing a Page as a web service, it's easy to include the fields of the table that the page is based on, but it's less clear how to include fields from another table.

Forum posts like this led me to believe that I couldn't expose flow fields in a Page web service, and I would get exceptions when I tried to expose all the fields of a table. In fact, it's perfectly possible to expose a flow field: it's flow filters that don't work with web services. But, I also didn't want to modify the underlying [job] table to add a flow field, and didn't see an easy way of adding a flow field to a Page. I tried "joining" the data in the C# application, but found network overhead made the application unusuably slow.

The solution to this problem was to use C/AL code to the Page to effectively create a lookup / flow field. This way, the data is "pre-joined" before leaving the NAV Server, which is fast and clean, but you didn't modify any tables. Here's how it's done:

Step 1. Add a Field with SourceExpression Set to a Function Name

To start, we create a Page using the wizard that includes all of the fields of an underlying table. Then, we create manually add fields that will contain the lookup data from other tables. The text in the SourceExpression column will be the name of the function that populates this field.

Step 2. Create Function in the Page's C/AL Code

With the Page field designer open, go to the functions tab of C/AL Globals form, and add a function with the name of the text in the SourceExpression column. Set the return type of the function with the "Locals" button, and a function trigger will appear in the C/AL code editor for your page. Add code to the body of the function trigger that will be called for each record to provide a value for the field.

Welcome to Hexo! This is your very first post. Check documentation for more info. If you get any problems when using Hexo, you can find the answer in troubleshooting or you can ask me on GitHub.

Quick Start

Create a new post

1

$ hexo new "My New Post"