Arguments to fmpz_CRT and fmpz_CRT_ui #1549
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fagu
commented
Oct 21, 2023
| fmpz_invmod(c, c, m2); | ||
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| if (fmpz_is_zero(c)) | ||
| if (!fmpz_invmod(c, c, m2)) |
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fmpz_invmod(f,g,h) returns 0 if g is not invertible modulo h. It doesn't necessarily set f=0.
fagu
commented
Oct 21, 2023
| @@ -61,12 +61,6 @@ void fmpz_CRT_ui(fmpz_t out, const fmpz_t r1, const fmpz_t m1, | |||
| c = fmpz_fdiv_ui(m1, m2); | |||
| c = n_invmod(c, m2); | |||
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| if (c == 0) | |||
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n_invmod(x,y) throws an exception if x is not invertible modulo y.
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This looks good. |
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The documentation of
fmpz_CRTrequires that the arguments m1 and m2 are greater than 1. If you pass m2=1, it currently prints the confusing messageException (fmpz_CRT). m1 not invertible modulo m2..I propose removing the requirement since it's not really used in the implementation anyways.
I haven't added any serious test with m1=1 or m2=1. (As far as I see, only the case where m2 is prime is currently tested, really...)
Maybe also make the parameters r2 and m2 const?