[gnumeric] sstest: fix some tests; widen acceptance range for bin tests

[Morten Welinder <mortenw src gnome org>]

commit c7ccb916d69110acd57bb9629f3381b2749a90b1
Author: Morten Welinder <terra gnome org>
Date:   Tue Mar 21 20:52:26 2017 -0400

    sstest: fix some tests; widen acceptance range for bin tests
    
    Avoid invalid parameters for df.
    Widen acceptance for bin tests to 4*sqrt(expected)
    
    This lowers the number of failures to something acceptable.

 ChangeLog    |    9 +++++++++
 NEWS         |    3 +++
 src/sstest.c |   13 +++++++------
 3 files changed, 19 insertions(+), 6 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index 90ff0c2..26a6160 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2017-03-21  Morten Welinder  <terra gnome org>
+
+       * src/sstest.c (rand_fractile_test): Allow 4*sqrt(expected)
+       deviation for each bin.
+       (test_random_randchisq, test_random_randtdist)
+       (test_random_randfdist): Don't allow df=0.
+       (test_random_randbeta): Don't floor the parameters thus avoiding
+       zero.
+
 2017-03-20  Morten Welinder <terra gnome org>
 
        * configure.ac: Post-release bump.
diff --git a/NEWS b/NEWS
index 6c393e9..e9ef541 100644
--- a/NEWS
+++ b/NEWS
@@ -1,5 +1,8 @@
 Gnumeric 1.12.35
 
+Morten:
+       * Test suite improvements.
+
 --------------------------------------------------------------------------
 Gnumeric 1.12.34
 
diff --git a/src/sstest.c b/src/sstest.c
index 38f9162..2abb64d 100644
--- a/src/sstest.c
+++ b/src/sstest.c
@@ -633,7 +633,7 @@ rand_fractile_test (gnm_float const *vals, int N, int nf,
 
        for (i = 1; i <= nf; i++) {
                gnm_float T = expected[i];
-               if (!(gnm_abs (fractilecount[i] - T) <= 3 * gnm_sqrt (T))) {
+               if (!(gnm_abs (fractilecount[i] - T) <= 4 * gnm_sqrt (T))) {
                        g_printerr ("Fractile test failure for bin %d.\n", i);
                        ok = FALSE;
                }
@@ -1343,7 +1343,8 @@ test_random_randbeta (int N)
        gnm_float mean, var, skew, kurt;
        gnm_float *vals;
        gboolean ok;
-       gnm_float param_a = gnm_floor (1 / (0.0001 + gnm_pow (random_01 (), 6)));       gnm_float param_b = 
gnm_floor (1 / (0.0001 + gnm_pow (random_01 (), 6)));
+       gnm_float param_a = 1 / (0.0001 + gnm_pow (random_01 (), 6));
+       gnm_float param_b = 1 / (0.0001 + gnm_pow (random_01 (), 6));
        gnm_float s = param_a + param_b;
        gnm_float mean_target = param_a / s;
        gnm_float var_target = mean_target * param_b / (s * (s + 1));
@@ -1423,7 +1424,7 @@ test_random_randtdist (int N)
        gnm_float mean, var, skew, kurt;
        gnm_float *vals;
        gboolean ok;
-       gnm_float param_df = gnm_floor (1 / (0.01 + gnm_pow (random_01 (), 6)));
+       gnm_float param_df = 1 + gnm_floor (1 / (0.01 + gnm_pow (random_01 (), 6)));
        gnm_float mean_target = 0;
        gnm_float var_target = param_df > 2 ? param_df / (param_df - 2) : gnm_nan;
        gnm_float skew_target = param_df > 3 ? 0 : gnm_nan;
@@ -1500,8 +1501,8 @@ test_random_randfdist (int N)
        gnm_float mean, var, skew, kurt;
        gnm_float *vals;
        gboolean ok;
-       gnm_float param_df1 = gnm_floor (1 / (0.01 + gnm_pow (random_01 (), 6)));
-       gnm_float param_df2 = gnm_floor (1 / (0.01 + gnm_pow (random_01 (), 6)));
+       gnm_float param_df1 = 1 + gnm_floor (1 / (0.01 + gnm_pow (random_01 (), 6)));
+       gnm_float param_df2 = 1 + gnm_floor (1 / (0.01 + gnm_pow (random_01 (), 6)));
        gnm_float mean_target = param_df2 > 2 ? param_df2 / (param_df2 - 2) : gnm_nan;
        gnm_float var_target = param_df2 > 4
                ? (2 * param_df2 * param_df2 * (param_df1 + param_df2 - 2) /
@@ -1581,7 +1582,7 @@ test_random_randchisq (int N)
        gnm_float mean, var, skew, kurt;
        gnm_float *vals;
        gboolean ok;
-       gnm_float param_df = gnm_floor (1 / (0.01 + gnm_pow (random_01 (), 6)));
+       gnm_float param_df = 1 + gnm_floor (1 / (0.01 + gnm_pow (random_01 (), 6)));
        gnm_float mean_target = param_df;
        gnm_float var_target = param_df * 2;
        gnm_float skew_target = gnm_sqrt (8 / param_df);