Message117675
| Author |
Kiriakos.Vlahos |
| Recipients |
Kiriakos.Vlahos, brian.curtin, eric.smith, loewis, mark.dickinson, sjmachin, skrah |
| Date |
2010年09月29日.23:26:39 |
| SpamBayes Score |
3.6134374e-05 |
| Marked as misclassified |
No |
| Message-id |
<1285802801.3.0.974327957001.issue9980@psf.upfronthosting.co.za> |
| In-reply-to |
| Content |
I found out that $x2xx (test both 12ドルxx and 02ドルxx) gives identical results to python. Here is what it means.
The PC field (bits 9 and 8) or Precision Control determines to what precision the FPU rounds results after each arithmetic instruction in one of three ways:
00 = 24 bits (REAL4)
01 = Not used
10 = 53 bits (REAL8) <- This is required by _Py_dg_dtoa
11 = 64 bits (REAL10) (this is the initialized state)
So contrary to my expectation it is not the rounding control bits but the Precision control bits that matter. |
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