Re: new snapshot?

[John W. Eaton]

On 26-Feb-2010, Michael D. Godfrey wrote:

| On 2/26/10 10:15 AM, Jaroslav Hajek wrote:
| > Are you sure? This is exactly the opposite of what I get. Sometimes
| > the assert fails with
| >
| > !!!!! test failed
| > assert (s (k:-1:1),s2,1e-10) expected
| >     38.060
| >     38.060
| >     38.034
| >     38.034
| >     38.015
| >     38.015
| >     38.004
| > but got
| >     38.060
| >     38.034
| >     38.034
| >     38.015
| >     38.015
| >     38.004
| >     38.004
| > maximum absolute error 0.0263523 exceeds tolerance 1e-10
| >
| > and the latter result is correct, AFAIK.
| >
| >    
| The latter result is s2  in the test.  This is what I get too.  s2, 
| computed from:
| [u2,s2,v2,flag] = svds(a,k,0);
| s2 = diag(s2);
| is correct.  It is the "expected" vector that is wrong.  This comes from:
| a = 
| 
sparse([3:n,1:n,1:(n-2)],[1:(n-2),1:n,3:n],[ones(1,n-2),0.4*n*ones(1,n),ones(1,n-2)]);
| [u,s,v] = svd(full(a));
| s = diag(s);
| [dum, idx] = sort(abs(s));
| s = s(idx);
| 
| Agree?

The problem is with svds, not svd on the full matrix.  I should have
put the arguments to assert in the opposite order.

Sorry for the confusion,

jwe