Return information

When SCS terminates it will return an ScsInfo struct containing the following fields.

Name	Type	Description
iter	scs_int	Number of iterations taken
status	char *	Status string (e.g., ‘solved’)
lin_sys_solver	char *	Linear system solver used
status_val	scs_int	Status integer exit flag
scale_updates	scs_int	Number of updates to the scale parameter (see Dynamic scale updating)
pobj	scs_float	Primal objective
dobj	scs_float	Dual objective
res_pri	scs_float	Primal residual (see termination conditions)
res_dual	scs_float	Dual residual (see termination conditions)
gap	scs_float	Absolute duality gap (see termination conditions)
res_infeas	scs_float	Primal infeasibility residual (see termination conditions)
res_unbdd_a	scs_float	Dual infeasibility residual involving \(A\) (see termination conditions)
res_unbdd_p	scs_float	Dual infeasibility residual involving \(P\) (see termination conditions)
comp_slack	scs_float	Complementary slackness (\(s^\top y\)), should be very close to zero
setup_time	scs_float	Time taken for setup (milliseconds)
solve_time	scs_float	Time taken for solve (milliseconds)
scale	scs_float	Final scale parameter, useful for initializing next solve (see Dynamic scale updating)
rejected_accel_steps	scs_int	Number of times an AA update was rejected by the safeguarding check (see Acceleration)
accepted_accel_steps	scs_int	Number of times an AA update was accepted by the safeguarding check (see Acceleration)
aa_stats	AaStats	Detailed AA solve diagnostics, including rejection causes, last rank, last weight norm, and last regularization
lin_sys_time	scs_float	Total time (milliseconds) spent in the linear system solver
cone_time	scs_float	Total time (milliseconds) spent in the cone projection
accel_time	scs_float	Total time (milliseconds) spent in the acceleration routine

Anderson acceleration statistics

The aa_stats field contains detailed diagnostics from the Anderson acceleration linear solves. These counters are useful for diagnosing whether AA is active and, when AA updates are rejected, why they were rejected.

Name	Type	Description
iter	scs_int	Internal AA iteration counter
n_accept	scs_int	Number of AA updates accepted by aa_apply before safeguarding
n_reject_lapack	scs_int	Number of AA updates rejected because the LAPACK solve failed
n_reject_rank0	scs_int	Number of AA updates rejected because rank truncation produced rank zero
n_reject_nonfinite	scs_int	Number of AA updates rejected because the AA weight norm was non-finite
n_reject_weight_cap	scs_int	Number of AA updates rejected because the AA weight norm exceeded the configured cap
n_safeguard_reject	scs_int	Number of AA updates rejected by the safeguarding check
last_rank	scs_int	Rank used in the most recent AA solve
last_aa_norm	scs_float	AA weight norm from the most recent AA solve, or NaN if no AA solve was attempted
last_regularization	scs_float	Regularization value used in the most recent AA solve