diff options
| -rw-r--r-- | ChangeLog | 7 | ||||
| -rw-r--r-- | ext/bigdecimal/bigdecimal.c | 17 |
2 files changed, 13 insertions, 11 deletions
@@ -1,3 +1,10 @@ +Sat Nov 23 19:46:00 2013 Kenta Murata <mrkn@mrkn.jp> + + * ext/bigdecimal/bigdecimal.c (BigMath_s_exp): Optimize the + calculation algorithm to reduce the number of divisions. + This optimization was proposed by Rafał Michalski. + [Feature #6857] [ruby-core:47130] + Sat Nov 23 19:20:00 2013 Kenta Murata <mrkn@mrkn.jp> * ext/bigdecimal/bigdecimal.c (BigDecimal_div2): The signature was diff --git a/ext/bigdecimal/bigdecimal.c b/ext/bigdecimal/bigdecimal.c index ab0fafb9b4..b4656ea0c3 100644 --- a/ext/bigdecimal/bigdecimal.c +++ b/ext/bigdecimal/bigdecimal.c @@ -2675,7 +2675,7 @@ BigMath_s_exp(VALUE klass, VALUE x, VALUE vprec) { ssize_t prec, n, i; Real* vx = NULL; - VALUE one, d, x1, y, z; + VALUE one, d, y; int negative = 0; int infinite = 0; int nan = 0; @@ -2751,11 +2751,9 @@ BigMath_s_exp(VALUE klass, VALUE x, VALUE vprec) } one = ToValue(VpCreateRbObject(1, "1")); - x1 = one; y = one; d = y; - z = one; - i = 0; + i = 1; while (!VpIsZero((Real*)DATA_PTR(d))) { SIGNED_VALUE const ey = VpExponent10(DATA_PTR(y)); @@ -2771,11 +2769,10 @@ BigMath_s_exp(VALUE klass, VALUE x, VALUE vprec) m = rmpd_double_figures(); } - x1 = BigDecimal_mult2(x1, x, SSIZET2NUM(n)); - ++i; - z = BigDecimal_mult(z, SSIZET2NUM(i)); - d = BigDecimal_div2(x1, z, SSIZET2NUM(m)); - y = BigDecimal_add(y, d); + d = BigDecimal_mult(d, x); /* d <- d * x */ + d = BigDecimal_div2(d, SSIZET2NUM(i), SSIZET2NUM(m)); /* d <- d / i */ + y = BigDecimal_add(y, d); /* y <- y + d */ + ++i; /* i <- i + 1 */ } if (negative) { @@ -2788,10 +2785,8 @@ BigMath_s_exp(VALUE klass, VALUE x, VALUE vprec) RB_GC_GUARD(one); RB_GC_GUARD(x); - RB_GC_GUARD(x1); RB_GC_GUARD(y); RB_GC_GUARD(d); - RB_GC_GUARD(z); } /* call-seq: |