[gnumeric] ebdo0: better fix.

[Morten Welinder <mortenw src gnome org>]

commit ff721c455911b3f8bf8cd1604ff7c5fc815686d1
Author: Morten Welinder <terra gnome org>
Date:   Wed Jan 6 21:42:34 2016 -0500

    ebdo0: better fix.

 src/mathfunc.c |   19 ++++++++++++-------
 1 files changed, 12 insertions(+), 7 deletions(-)
---
diff --git a/src/mathfunc.c b/src/mathfunc.c
index efd2de9..85fed5b 100644
--- a/src/mathfunc.c
+++ b/src/mathfunc.c
@@ -240,27 +240,32 @@ static const float bd0_scale[128 + 1][4] = {
 static void
 ebd0(gnm_float x, gnm_float M, gnm_float *yh, gnm_float *yl)
 {
-       gnm_float r, r1, r2, f, fg, M1;
-       int e, e1, e2;
+       gnm_float r, f, fg, M1;
+       int e;
        int i, j;
        const int Sb = 10;
        const double S = 1u << Sb;
        const int N = G_N_ELEMENTS(bd0_scale) - 1;
+       const double e4 = GNM_EPSILON * GNM_EPSILON * GNM_EPSILON * GNM_EPSILON;
 
        *yl = *yh = 0;
 
        if (x == M) return;
-       if (x == 0) { PAIR_ADD(M, *yh, *yl); return; }
+       if (x < M * e4) { PAIR_ADD(M, *yh, *yl); return; }
        if (M == 0) { *yh = gnm_pinf; return; }
 
+       if (M < x * e4) {
+               PAIR_ADD(x * (gnm_log(x) - 1), *yh, *yl);
+               PAIR_ADD(-x * gnm_log(M), *yh, *yl);
+               return;
+       }
+
 #ifdef DEBUG_EBD0
        g_printerr ("x=%.20g  M=%.20g\n", x, M);
+       g_printerr ("x/M=%.20g\n", x / M);
 #endif
 
-       r1 = gnm_frexp (M, &e1);
-       r2 = gnm_frexp (x, &e2);
-       r = gnm_frexp (r1 / r2, &e);
-       e += (e1 - e2);
+       r = gnm_frexp (M / x, &e);
        i = gnm_floor ((r - 0.5) * (2 * N) + 0.5);
        g_assert (i >= 0 && i <= N);
        f = gnm_floor (S / (0.5 + i / (2.0 * N)) + 0.5);