Hi, all
Specifically, I’m trying to solve a problem with the objective function of a l2-norm minus an affine function as follow,
f=||w||_2^2-(a*(y-x))
where w and y are optimization variables, a and x are kown parameters.
My confusion is that the final result is different from the iterative information. As you can see in the following, the iterative information shows that the result would be -2.67. However, the CVX demonstrates that the optimal value is -1.88. So could you please help me to explain this phenomenon? And which is the real optimal value?
I appreciate your kind help!
The following is the iterative information.
Calling SDPT3 4.0: 1097 variables, 513 equality constraints
num. of constraints = 513
dim. of socp var = 1097, num. of socp blk = 43
SDPT3: Infeasible path-following algorithms
version predcorr gam expon scale_data
NT 1 0.000 1 0
it pstep dstep pinfeas dinfeas gap prim-obj dual-obj cputime
0|0.000|0.000|4.2e+00|7.1e+03|5.4e+05| 5.742654e-01 0.000000e+00| 0:0:00| spchol 1 1
1|0.865|0.768|5.7e-01|1.6e+03|1.2e+05| 8.931482e-01 -2.780834e+04| 0:0:00| spchol 1 1
2|1.000|0.832|3.6e-05|2.7e+02|2.1e+04| 1.507160e+00 -1.020520e+04| 0:0:01| spchol 1 1
3|1.000|0.986|6.6e-05|3.8e+00|2.8e+02| 1.501680e+00 -1.399625e+02| 0:0:01| spchol 1 1
4|1.000|0.897|8.6e-07|3.9e-01|3.0e+01| 1.164379e+00 -1.442595e+01| 0:0:01| spchol 1 1
5|0.698|0.768|7.3e-07|9.0e-02|7.6e+00|-1.577403e-02 -4.422429e+00| 0:0:01| spchol 1 1
6|0.574|0.601|6.1e-07|3.6e-02|3.2e+00|-1.024427e+00 -2.957142e+00| 0:0:01| spchol 1 1
7|0.598|0.583|3.5e-07|1.5e-02|1.3e+00|-1.579591e+00 -2.386611e+00| 0:0:01| spchol 1 1
8|0.360|0.417|2.5e-07|8.8e-03|8.1e-01|-1.799819e+00 -2.245807e+00| 0:0:01| spchol 1 1
9|0.420|0.427|1.6e-07|5.0e-03|4.6e-01|-1.969387e+00 -2.173095e+00| 0:0:01| spchol 1 1
10|0.654|0.498|5.6e-08|2.5e-03|2.3e-01|-2.086029e+00 -2.161848e+00| 0:0:01| spchol 1 1
11|0.490|0.509|2.8e-08|1.2e-03|1.2e-01|-2.141224e+00 -2.166201e+00| 0:0:01| spchol 1 1
12|0.271|0.334|2.1e-08|8.3e-04|8.7e-02|-2.170143e+00 -2.175627e+00| 0:0:01| spchol 1 1
13|0.025|0.024|2.0e-08|8.1e-04|8.7e-02|-2.216368e+00 -2.176581e+00| 0:0:01| spchol 1 1
14|0.020|0.081|2.0e-08|7.4e-04|9.4e-02|-2.278096e+00 -2.193888e+00| 0:0:01| spchol 1 1
15|0.122|0.094|1.7e-08|6.7e-04|1.0e-01|-2.352233e+00 -2.213373e+00| 0:0:01| spchol 1 1
16|0.056|0.124|1.6e-08|5.9e-04|1.1e-01|-2.371701e+00 -2.246003e+00| 0:0:01| spchol 1 1
17|0.205|0.108|1.3e-08|5.2e-04|1.2e-01|-2.436082e+00 -2.271779e+00| 0:0:01| spchol 1 1
18|0.190|0.194|1.1e-08|4.2e-04|1.3e-01|-2.494459e+00 -2.330681e+00| 0:0:01| spchol 1 1
19|0.222|0.236|8.2e-09|3.2e-04|1.3e-01|-2.540943e+00 -2.395769e+00| 0:0:01| spchol 1 1
20|0.167|0.209|6.9e-09|2.6e-04|1.2e-01|-2.572555e+00 -2.446362e+00| 0:0:01| spchol 1 1
21|0.254|0.403|5.1e-09|1.5e-04|9.7e-02|-2.605267e+00 -2.529890e+00| 0:0:01| spchol 1 1
22|0.462|0.422|2.8e-09|8.8e-05|6.4e-02|-2.639981e+00 -2.586446e+00| 0:0:01| spchol 1 1
23|0.699|0.592|8.3e-10|3.6e-05|2.8e-02|-2.661479e+00 -2.636792e+00| 0:0:01| spchol 1 1
24|0.790|0.561|1.7e-10|1.6e-05|1.1e-02|-2.670405e+00 -2.657154e+00| 0:0:01| spchol 1 1
25|0.834|0.828|2.9e-11|2.7e-06|2.1e-03|-2.672510e+00 -2.670298e+00| 0:0:01| spchol 1 1
26|0.923|0.796|7.0e-12|5.6e-07|3.7e-04|-2.673037e+00 -2.672527e+00| 0:0:01| spchol 1 1
27|0.853|0.766|4.8e-12|1.3e-07|8.2e-05|-2.673101e+00 -2.672978e+00| 0:0:01| spchol 1 1
28|0.784|0.804|2.2e-11|2.6e-08|1.8e-05|-2.673114e+00 -2.673092e+00| 0:0:01| spchol 1 1
29|0.792|0.563|3.4e-11|1.1e-08|6.7e-06|-2.673119e+00 -2.673108e+00| 0:0:01| spchol 1 1
30|0.784|0.643|9.1e-11|4.0e-09|2.3e-06|-2.673120e+00 -2.673116e+00| 0:0:01| spchol 1 1
31|0.853|0.652|2.1e-09|1.4e-09|7.5e-07|-2.673120e+00 -2.673119e+00| 0:0:01| spchol 1 1
32|0.980|0.484|6.9e-09|7.2e-10|3.6e-07|-2.673120e+00 -2.673119e+00| 0:0:01| spchol 1 1
33|1.000|0.483|3.2e-09|3.8e-10|2.0e-07|-2.673120e+00 -2.673120e+00| 0:0:01| spchol 1 1
34|1.000|0.484|7.4e-10|2.0e-10|1.1e-07|-2.673120e+00 -2.673120e+00| 0:0:01| spchol 1 1
35|1.000|0.485|9.5e-10|1.1e-10|6.4e-08|-2.673120e+00 -2.673120e+00| 0:0:01|
stop: max(relative gap, infeasibilities) < 1.49e-08
number of iterations = 35
primal objective value = -2.67312018e+00
dual objective value = -2.67312007e+00
gap := trace(XZ) = 6.42e-08
relative gap = 1.01e-08
actual relative gap = -1.70e-08
rel. primal infeas (scaled problem) = 9.51e-10
rel. dual " " " = 1.09e-10
rel. primal infeas (unscaled problem) = 0.00e+00
rel. dual " " " = 0.00e+00
norm(X), norm(y), norm(Z) = 3.4e+03, 4.0e-01, 5.9e-01
norm(A), norm(b), norm© = 1.1e+04, 1.1e+01, 1.5e+00
Total CPU time (secs) = 1.09
CPU time per iteration = 0.03
termination code = 0
DIMACS: 3.3e-09 0.0e+00 1.5e-10 0.0e+00 -1.7e-08 1.0e-08
Status: Solved
Optimal value (cvx_optval): -1.88714