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ext/bcmath: Performance improvement bcsqrt() #18771

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ext/bcmath: Performance improvement bcsqrt() #18771

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57b91d6
local_num is not needed so it has been removed.
SakiTakamachi Jun 5, 2025
0b34dfd
Optimized and changed the initialization process to run a little later.
SakiTakamachi Jun 5, 2025
bb71577
create fast path and move old logic to standard path
SakiTakamachi Jun 7, 2025
975fcc4
Optimized standard path calculation
SakiTakamachi Jun 8, 2025
f6c50d8
Efficiently obtain the initial value for the standard path.
SakiTakamachi Jun 9, 2025
dd64d94
Omit low precision digits in calculations
SakiTakamachi Jun 10, 2025
d7d1d80
Added test cases
SakiTakamachi Jun 11, 2025
aef9c17
removed nearzero.c
SakiTakamachi Jun 11, 2025
7555b2f
Removed `bc_add_ex`, `bc_int2num`, and `bc_raise_bc_exponent` as they…
SakiTakamachi Jun 12, 2025
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13 changes: 6 additions & 7 deletions ext/bcmath/libbcmath/src/sqrt.c
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Original file line number Diff line number Diff line change
Expand Up @@ -38,20 +38,19 @@

bool bc_sqrt(bc_num *num, size_t scale)
{
const bc_num local_num = *num;
/* Initial checks. */
if (bc_is_neg(local_num)) {
if (bc_is_neg(*num)) {
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One thing I wonder is whether this was the right move.
One the one hand, keeping *num in a local variable may save a pointer load, on the other hand it may get spilled in between calls anyway.

/* Cannot take the square root of a negative number */
return false;
}
/* Square root of 0 is 0 */
if (bc_is_zero(local_num)) {
if (bc_is_zero(*num)) {
bc_free_num (num);
*num = bc_copy_num(BCG(_zero_));
return true;
}

bcmath_compare_result num_cmp_one = bc_compare(local_num, BCG(_one_), local_num->n_scale);
bcmath_compare_result num_cmp_one = bc_compare(*num, BCG(_one_), (*num)->n_scale);
/* Square root of 1 is 1 */
if (num_cmp_one == BCMATH_EQUAL) {
bc_free_num (num);
Expand All @@ -62,7 +61,7 @@ bool bc_sqrt(bc_num *num, size_t scale)
/* Initialize the variables. */
size_t cscale;
bc_num guess, guess1, point5, diff;
size_t rscale = MAX(scale, local_num->n_scale);
size_t rscale = MAX(scale, (*num)->n_scale);

bc_init_num(&guess1);
bc_init_num(&diff);
Expand All @@ -74,13 +73,13 @@ bool bc_sqrt(bc_num *num, size_t scale)
if (num_cmp_one == BCMATH_RIGHT_GREATER) {
/* The number is between 0 and 1. Guess should start at 1. */
guess = bc_copy_num(BCG(_one_));
cscale = local_num->n_scale;
cscale = (*num)->n_scale;
} else {
/* The number is greater than 1. Guess should start at 10^(exp/2). */
bc_init_num(&guess);
bc_int2num(&guess, 10);

bc_int2num(&guess1, local_num->n_len);
bc_int2num(&guess1, (*num)->n_len);
bc_multiply_ex(guess1, point5, &guess1, 0);
guess1->n_scale = 0;
bc_raise_bc_exponent(guess, guess1, &guess, 0);
Expand Down