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ex-2/fancier: optimise out an operation

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This commit is contained in:
Michele Guerini Rocco 2020-05-24 23:11:29 +02:00
parent f73c9b14b3
commit 845548fa93
1 changed files with 4 additions and 7 deletions
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11
ex-2/fancier.c
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@ -340,20 +340,17 @@ void mpq_log_ui(mpq_t rop, size_t x, size_t digits) {
mpq_div(low, term, temp);
mpq_add(low, sum, low);
/* Average the two bounds */
/* Average the two bounds
* Note: we don't divive the sum by 2 because we
* actually need 2 Σ_{k=0} y^(2k+1)/(2k+1).
*/
mpq_add(sum, low, upp);
mpz_div_ui(mpq_numref(sum), mpq_numref(sum), 2);
mpq_canonicalize(sum);
size_t d = digits > 50 ? 50 : digits;
mpq_fprintf(stderr, d+2, "[mpq_log_ui] upper bound: %q...\n", upp);
mpq_fprintf(stderr, d+2, "[mpq_log_ui] lower bound: %q...\n", low);
mpq_fprintf(stderr, d, "[mpq_log_ui] series: %q...\n", sum);
// multiply by 2
mpz_mul_ui(mpq_numref(sum), mpq_numref(sum), 2);
mpq_canonicalize(sum);
// calculate log(2)*(m-1)
mpq_t log2; mpq_init(log2);
mpq_log2(log2, digits);