Does Google Have Changed His Algorithm of Indexing Rate of Web Pages?

Since last two months I have been regularly looking that Google crawl rate of the website pages has gone down. I have checked many website pages daily and I got there pages are indexing OR crawling within 2 to 3 weeks of period. Why is it happening? Does Google have changed his algorithm of crawling the pages?

Many people have discussed the question to the webmaster forum. They want to know the genuine reason of the delay rate of page crawling.

I was followed some independent website, those were indexed or crawled by the Google on the daily basis. Currently those website are indexing between 2 or 3 weeks late. In this condition website owners think that there will be some error in robots.txt file the website.

One person had asked to me "Hi! This is my website [http://example.com/] and It was crawled every day. But since last months of the June, I have been looking my website indexing is being crawled between 2 weeks late."

I understand that Google does not index the entire sitemap but why is the "already" indexed URL going down?  Does this have to do with the new Canonical rules?

I have replied him to check your sitemap URL and resubmit your sitemap URL to the Google.

After 2 day later he replied me as: “I have checked my website sitemap URL and resubmit the sitemap again and again but I am facing same problem of my web page indexing, not only homepage rather than deep links are also delayed."

Here is some discussion from the webmasters click here to check the discussion.

From Exellweb Marketing,  SEO