{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

cs lecture oct 26

# cs lecture oct 26 - Representing the Web struct link int...

This preview shows pages 1–4. Sign up to view the full content.

cs lecture oct 26 How does Google read your mind? (organic ranking) -structure and content of web pages (Including anchor text) -user behavior (implicit user feedback), frequency of clicks on first/2 nd or third link, then re-rank -“quality” of page; static rank; (eg. PageRank) Random surfer model: SEO -pretend you’re surfing randomly -At each step you either a. follow a link (probability x) or b. jump to a random page (probability 1- x) defn: the PageRank – R(a) of a page Q is the probability you’re on a page Q after surfing for a long time. Computing PageRank ~R(Q) R(Q) = (1-&)/N +

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
note & = delta let & = 80%=4/5=>(1-&)/N=1/15 System of linear equations x=1/15 +4/5 y y=1/15 + 2/5 x + 4/5 z z= 1/15 + 2/5 x x=61/159 = 0.383648 y=0.396326 = 21/53 z=0.22613 35/159 Solve with fixed point iteration initial guess x=y=z=1/3=0.3333333333333333333333’ new x = 1/15 + 4/5 y new y = 1/15 + 2/5 x + 4/5 z old guesses new z = 1/5 + 2/5 x x y z 0 0.333 0.333 0.333 1 0.333 0.467 0.233 2 0.440 0.360 0.200 11 0.383 0.396 0.222 20 ITERATIONS => 5 digits of accuracy

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Representing the Web struct link { int src,dst; }; struck link l={{0,1},{0,2},{1,0},{2,1}}; void pagerank (struct link l, int links, double r, int pages,double delta, int iterations) { /* Assume pages, links, iterations > 0 Assume 0<delta<1 Assumes src, dst, etc. correct Assumes not sinks */ int i,j double s[pages]; - C99 int out[pages]; /* compute number of outlinks for each page */ for(j=0;j<pages;j++) out[j]=0; for (j=0;i<links;j++) out[l[j].src]++; /* initial guess */ for(j=0;j<pages;i++) r[j]=1.0/pages; for(i=0; i<iterations; i++){ /* new ranks computed in s */ for(j=0;j<pages;j++) s[j]=(1-delta)/pages; /* apply links */ for(j=0;j<links;j++) s[l[j].dst] +=delta*r[l[j].src]/out[l[j].src]; /* update r*/ for(j=0;j<pages;j++) r[j]=s[j]; int main(void) { int I; double r[3]; struck link l={{0,1},{0,2},{1,0},{2,1}}; pagerank(l,4,r,3,0.80,20); for(i=0;i<3;i++) printf(“%g\n”,r[i]); return 0; }...
View Full Document

{[ snackBarMessage ]}

### Page1 / 4

cs lecture oct 26 - Representing the Web struct link int...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online