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Table 7 Numbers of GCR iterations to convergence on ill-posed problems

From: Newton–Raphson preconditioner for Krylov type solvers on GPU devices

  DIAG SSOR BFGS–DIAG BFGS–SSOR
m = 3 m = 5 m = 7 m = 10 m = 3 m = 5 m = 7 m = 10
\(40 \times 40 \times 125\) 3930 341 878 900 964 891 165 210 248 267
\(20 \times 20 \times 500\) NA 1817 7709 4994 7690 NA 1188 1187 926 1256
\(10 \times 10 \times 2000\) NA 25,209 NA NA NA NA 8736 9954 7088 NA
  1. In the table, NA denotes the preconditioned GCR doesn’t converge within 300,000 iterations, and m denotes the number of previous iterations to be taken into consideration