Increase float16 randomized test coverage

Raise sample sizes for float16 arithmetic, conversion, unary, and pow tests.

eval.py

@@ -2616,8 +2616,8 @@ def test_float16_arithmetic(ctx: EvalContext) -> List[TestResult]:
     results = []
 
     rng = random.Random(0xF00D)
-    light_pairs = build_float16_pairs(rng, 256)
-    heavy_pairs = build_float16_pairs(rng, 128)
+    light_pairs = build_float16_pairs(rng, 2048)
+    heavy_pairs = build_float16_pairs(rng, 1024)
 
     # Addition - randomized evaluation
     if f"float16.add.exp_a_all_ones.weight" in ctx.tensors:
@@ -2756,7 +2756,7 @@ def test_float16_conversion(ctx: EvalContext) -> List[TestResult]:
             0x0400, 0x0001, 0x03FF, 0x3555, 0x3E00,
         ]
         test_bits = list(edge_vals)
-        while len(test_bits) < 256:
+        while len(test_bits) < 1024:
             v = rng.getrandbits(16)
             if float16_is_nan_bits(v):
                 continue
@@ -2796,7 +2796,7 @@ def test_float16_conversion(ctx: EvalContext) -> List[TestResult]:
 
         edge_ints = [0, 1, -1, 2, -2, 100, -100, 32767, -32768]
         test_vals = list(edge_ints)
-        while len(test_vals) < 256:
+        while len(test_vals) < 1024:
             test_vals.append(rng.randint(-32768, 32767))
 
         for val in test_vals:
@@ -2825,7 +2825,7 @@ def test_float16_unary(ctx: EvalContext) -> List[TestResult]:
     results: List[TestResult] = []
 
     rng = random.Random(1337)
-    values = build_float16_values(rng, 256)
+    values = build_float16_values(rng, 1024)
 
     ops = [
         ("float16.sqrt", "sqrt"),
@@ -2990,7 +2990,7 @@ def test_float16_pow(ctx: EvalContext) -> List[TestResult]:
         return results
 
     rng = random.Random(1337)
-    pairs = build_float16_pairs(rng, 128)
+    pairs = build_float16_pairs(rng, 512)
     mul_prefix = "float16.pow.mul"
     mul_gates = sorted([g for g in ctx.gates if g.startswith(mul_prefix + ".")])