[Piglit] [PATCH 1/5] cl: Fix ulp tolerance comparison

[Jan Vesely]

This fails sin/cos/tan tests almost everywhere.

Signed-off-by: Jan Vesely <jano.ves...@gmail.com>
---
 tests/util/piglit-util-cl.c | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/tests/util/piglit-util-cl.c b/tests/util/piglit-util-cl.c
index 0211c1ff6..0cbc450ad 100644
--- a/tests/util/piglit-util-cl.c
+++ b/tests/util/piglit-util-cl.c
@@ -89,21 +89,27 @@ piglit_cl_probe_floating(float value, float expect,  
uint32_t ulp)
        union {
                float f;
                uint32_t u;
-       } v, e, t;
+       } v, e;
 
        v.f = value;
        e.f = expect;
-       t.u = ulp;
-       /* Treat infinity and nan seperately */
+
+       /* Treat infinity and nan separately */
        if (probe_float_check_nan_inf(value, expect)) {
                return true;
        }
 
+       /* expect is correctly rounded, 1 ULP is the distance to next
+        * representable value */
+       float direction = signbit(expect) ?  -INFINITY : INFINITY;
+       float one_ulp = nextafterf(expect, direction) - expect;
+       float tolerance = fabsf(ulp * one_ulp);
+
        diff = fabsf(value - expect);
 
-       if(diff > ulp || isnan(value)) {
+       if (diff > tolerance || isnan(value)) {
                printf("Expecting %f (0x%x) with tolerance %f (%u ulps), but 
got %f (0x%x)\n",
-                      e.f, e.u, t.f, t.u, v.f, v.u);
+                      e.f, e.u, tolerance, ulp, v.f, v.u);
                return false;
        }
 
@@ -117,21 +123,25 @@ piglit_cl_probe_double(double value, double expect, 
uint64_t ulp)
        union {
                double f;
                uint64_t u;
-       } v, e, t;
+       } v, e;
 
        v.f = value;
        e.f = expect;
-       t.u = ulp;
-       /* Treat infinity and nan seperately */
+
+       /* Treat infinity and nan separately */
        if (probe_float_check_nan_inf(value, expect)) {
                return true;
        }
 
-       diff = fabsl(value - expect);
+       double direction = signbit(expect) ?  -INFINITY : INFINITY;
+       double one_ulp = nextafter(expect, direction) - expect;
+       double tolerance = fabs(ulp * one_ulp);
+
+       diff = fabs(value - expect);
 
-       if(diff > ulp || isnan(value)) {
+       if(diff > tolerance || isnan(value)) {
                printf("Expecting %f (0x%" PRIx64") with tolerance %f (%lu 
ulps), but got %f (0x%" PRIx64")\n",
-                      e.f, e.u, t.f, t.u, v.f, v.u);
+                      e.f, e.u, tolerance, ulp, v.f, v.u);
                return false;
        }
 
-- 
2.13.6

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