Single-precision in the tangent-linear and adjoint models of incremental 4D-VAr
The use of single-precision arithmetic in ECMWF’s forecasting model gave a 40% reduction in wall-clock time over double-precision, with no decrease in forecast quality. However, using reduced-precision in 4D-Var data assimilation is relatively unexplored and there are potential issues with using sin...
| Hlavní autoři: | , , , |
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| Médium: | Journal article |
| Jazyk: | English |
| Vydáno: |
American Meteorological Society
2020
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| _version_ | 1826299829516500992 |
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| author | Hatfield, S McRae, A Palmer, T Düben, P |
| author_facet | Hatfield, S McRae, A Palmer, T Düben, P |
| author_sort | Hatfield, S |
| collection | OXFORD |
| description | The use of single-precision arithmetic in ECMWF’s forecasting model gave a 40% reduction in wall-clock time over double-precision, with no decrease in forecast quality. However, using reduced-precision in 4D-Var data assimilation is relatively unexplored and there are potential issues with using single-precision in the tangent-linear and adjoint models. Here, we present the results of reducing numerical precision in an incremental 4D-Var data assimilation scheme, with an underlying two-layer quasigeostrophic model. The minimizer used is the conjugate gradient method. We show how reducing precision increases the asymmetry between the tangent-linear and adjoint models. For ill-conditioned problems, this leads to a loss of orthogonality among the residuals of the conjugate gradient algorithm, which slows the convergence of the minimization procedure. However, we also show that a standard technique, reorthogonalization, eliminates these issues and therefore could allow the use of single-precision arithmetic. This work is carried out within ECMWF’s data assimilation framework, the Object Oriented Prediction System. |
| first_indexed | 2024-03-07T05:07:54Z |
| format | Journal article |
| id | oxford-uuid:da8fef1e-4ab8-4cae-8ff3-9a53cbbf862c |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T05:07:54Z |
| publishDate | 2020 |
| publisher | American Meteorological Society |
| record_format | dspace |
| spelling | oxford-uuid:da8fef1e-4ab8-4cae-8ff3-9a53cbbf862c2022-03-27T09:04:07ZSingle-precision in the tangent-linear and adjoint models of incremental 4D-VArJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:da8fef1e-4ab8-4cae-8ff3-9a53cbbf862cEnglishSymplectic ElementsAmerican Meteorological Society2020Hatfield, SMcRae, APalmer, TDüben, PThe use of single-precision arithmetic in ECMWF’s forecasting model gave a 40% reduction in wall-clock time over double-precision, with no decrease in forecast quality. However, using reduced-precision in 4D-Var data assimilation is relatively unexplored and there are potential issues with using single-precision in the tangent-linear and adjoint models. Here, we present the results of reducing numerical precision in an incremental 4D-Var data assimilation scheme, with an underlying two-layer quasigeostrophic model. The minimizer used is the conjugate gradient method. We show how reducing precision increases the asymmetry between the tangent-linear and adjoint models. For ill-conditioned problems, this leads to a loss of orthogonality among the residuals of the conjugate gradient algorithm, which slows the convergence of the minimization procedure. However, we also show that a standard technique, reorthogonalization, eliminates these issues and therefore could allow the use of single-precision arithmetic. This work is carried out within ECMWF’s data assimilation framework, the Object Oriented Prediction System. |
| spellingShingle | Hatfield, S McRae, A Palmer, T Düben, P Single-precision in the tangent-linear and adjoint models of incremental 4D-VAr |
| title | Single-precision in the tangent-linear and adjoint models of incremental 4D-VAr |
| title_full | Single-precision in the tangent-linear and adjoint models of incremental 4D-VAr |
| title_fullStr | Single-precision in the tangent-linear and adjoint models of incremental 4D-VAr |
| title_full_unstemmed | Single-precision in the tangent-linear and adjoint models of incremental 4D-VAr |
| title_short | Single-precision in the tangent-linear and adjoint models of incremental 4D-VAr |
| title_sort | single precision in the tangent linear and adjoint models of incremental 4d var |
| work_keys_str_mv | AT hatfields singleprecisioninthetangentlinearandadjointmodelsofincremental4dvar AT mcraea singleprecisioninthetangentlinearandadjointmodelsofincremental4dvar AT palmert singleprecisioninthetangentlinearandadjointmodelsofincremental4dvar AT dubenp singleprecisioninthetangentlinearandadjointmodelsofincremental4dvar |