[gnumeric] Solver: line search fix if we start from 0.

[Morten Welinder <mortenw src gnome org>]

commit ee9550b07fea46ab629cceb120f93b3c805bb277
Author: Morten Welinder <terra gnome org>
Date:   Tue May 5 21:45:56 2015 -0400

    Solver: line search fix if we start from 0.

 src/tools/gnm-solver.c |   19 ++++++++++++-------
 1 files changed, 12 insertions(+), 7 deletions(-)
---
diff --git a/src/tools/gnm-solver.c b/src/tools/gnm-solver.c
index e6c0f25..846aa00 100644
--- a/src/tools/gnm-solver.c
+++ b/src/tools/gnm-solver.c
@@ -2656,17 +2656,22 @@ cb_polish_iter (GnmSolverIterator *iter, GnmIterSolver *isol)
 
        dir = g_new0 (gnm_float, n);
        for (c = 0; c < n; c++) {
-               gnm_float s, y, s0, xc = isol->xk[c];
-               int e;
+               gnm_float s, y, s0, sm, xc = isol->xk[c];
 
-               (void)gnm_frexp (xc, &e);
-               s0 = gnm_ldexp (1, e - 10);
-               if (s0 == 0) s0 = GNM_MIN;
+               if (xc == 0) {
+                       s0 = 0.5;
+                       sm = 1;
+               } else {
+                       int e;
+                       (void)gnm_frexp (xc, &e);
+                       s0 = gnm_ldexp (1, e - 10);
+                       if (s0 == 0) s0 = GNM_MIN;
+                       sm = gnm_abs (xc);
+               }
 
                dir[c] = 1;
                s = gnm_solver_line_search (sol, isol->xk, dir, TRUE,
-                                           s0, gnm_abs (xc), 0.0,
-                                           &y);
+                                           s0, sm, 0.0, &y);
                dir[c] = 0;
 
                if (gnm_finite (s)) {