Allocate minimum necessary digits for quotient and remainder#326
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Allocate minimum necessary digits for quotient and remainder#326tompng wants to merge 2 commits into
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tompng
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May 24, 2025
| word_r = r->MaxPrec; | ||
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| if (word_a >= word_r) goto space_error; | ||
| if (word_a >= word_r || word_b + word_c - 2 >= word_r) goto space_error; |
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There are two more goto space_error in this function.
One is on L6218
ind_r = ind_c + ind_b;
if (ind_r >= word_r) goto space_error;And another in L6253
ind_r = b->Prec + ind_c - 1; // L6242
ind_r = b->Prec + ind_c; // L6250 (ind_c + 1 < word_c is ensured in L6247)
if (ind_r >= word_r) goto space_error;Both has the same requirement: (word_b-1) + (word_c-1) < word_r
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| mx = ((a_prec > b_prec) ? a_prec : b_prec) + BIGDECIMAL_DOUBLE_FIGURES; | ||
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| if (2*BIGDECIMAL_DOUBLE_FIGURES > mx) | ||
| mx = 2*BIGDECIMAL_DOUBLE_FIGURES; |
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Precision was max(a_prec*2, b_prec*2, 32).
I think we normally need max(a_prec, b_prec) + extra precision, and the extra part was ≧16 before.
Fixes wrong calculation of quotient and remainder precision in `a / b` division. Precision of quotient is sufficient enough with `[a_prec,b_prec].max+extra`. Required remainder allocation size can be calculated from requirements of VpDivd. VpDivd requires `r_maxprec > a_prec` and `r_maxprec > b_prec+c_maxprec-2`.
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Fixes #220 and #222
Fixes wrong calculation of quotient and remainder precision in
a / bdivision.Precision of quotient is sufficient enough with
[a_prec,b_prec].max+extra.Required remainder allocation size can be calculated from requirements of VpDivd.
VpDivd requires
r_maxprec > a_precandr_maxprec > b_prec+c_maxprec-2.