MAINT: Improve float16 and float32 printing

f2013519 · f2013519 · commit 5f0f716daeed · 2025-04-14T20:46:19.000+05:30
diff --git a/numpy/_core/arrayprint.py b/numpy/_core/arrayprint.py
@@ -990,11 +990,19 @@ def fillFormat(self, data):
 
         # choose exponential mode based on the non-zero finite values:
         abs_non_zero = absolute(finite_vals[finite_vals != 0])
+
+        # consider data type while deciding the max cutoff for exp format
+        exp_cutoff_max = 1.e8
+        if data.dtype == "float16":
+            exp_cutoff_max = 1.e3
+        elif data.dtype == "float32":
+            exp_cutoff_max = 1.e7
+
         if len(abs_non_zero) != 0:
             max_val = np.max(abs_non_zero)
             min_val = np.min(abs_non_zero)
             with errstate(over='ignore'):  # division can overflow
-                if max_val >= 1.e8 or (not self.suppress_small and
+                if max_val >= exp_cutoff_max or (not self.suppress_small and
                         (min_val < 0.0001 or max_val / min_val > 1000.)):
                     self.exp_format = True
 
diff --git a/numpy/_core/src/multiarray/scalartypes.c.src b/numpy/_core/src/multiarray/scalartypes.c.src
@@ -1304,8 +1304,12 @@ legacy_@name@_format@kind@(npy_@name@ val){
 
 #define IS_@kind@
 
+#define SINGLE_TYPE 0
+#define DOUBLE_TYPE 1
+#define LONG_TYPE 2
 /**begin repeat1
  * #name = float, double, longdouble#
+ * #dtype = 0, 1, 2#
  * #Name = Float, Double, LongDouble#
  * #NAME = FLOAT, DOUBLE, LONGDOUBLE#
  * #n = f, , l#
@@ -1336,7 +1340,11 @@ static PyObject *
     }
     else {
         npy_@name@ absval = val < 0 ? -val : val;
-        use_positional = absval < 1.e16L && absval >= 1.e-4L;
+        #if @dtype@ == SINGLE_TYPE
+            use_positional = absval < 1.e7L && absval >= 1.e-4L;
+        #else
+            use_positional = absval < 1.e16L && absval >= 1.e-4L;
+        #endif
     }
 
     if (use_positional) {
@@ -1485,7 +1493,7 @@ halftype_@kind@(PyObject *self)
     absval = floatval < 0 ? -floatval : floatval;
 
     PyObject *string;
-    if (absval == 0 || (absval < 1.e16 && absval >= 1.e-4) ) {
+    if (absval == 0 || (absval < 1.e3 && absval >= 1.e-4) ) {
         string = format_half(val, 0, -1, 0, TrimMode_LeaveOneZero, -1, -1, -1);
     }
     else {
diff --git a/numpy/_core/tests/test_arrayprint.py b/numpy/_core/tests/test_arrayprint.py
@@ -919,6 +919,21 @@ def test_floatmode(self):
         a = np.float64.fromhex('-1p-97')
         assert_equal(np.float64(np.array2string(a, floatmode='unique')), a)
 
+    def test_gh_28679(self):
+        # test cutoff to exponent notation for half, single, and complex64
+        a = np.half([999, 999])
+        b = np.half([999, 1000])
+        c = np.single([9999999, 9999999])
+        d = np.single([9999999, -10000000])
+        e = np.complex64([9999999 + 9999999j, 9999999 + 9999999j])
+        f = np.complex64([9999999 + 9999999j, 9999999 + -10000000j])
+        assert_equal(str(a), "[999. 999.]")
+        assert_equal(str(b), "[9.99e+02 1.00e+03]")
+        assert_equal(str(c), "[9999999. 9999999.]")
+        assert_equal(str(d), "[ 9.999999e+06 -1.000000e+07]")
+        assert_equal(str(e), "[9999999.+9999999.j 9999999.+9999999.j]")
+        assert_equal(str(f), "[9999999.+9.999999e+06j 9999999.-1.000000e+07j]")
+
     def test_legacy_mode_scalars(self):
         # in legacy mode, str of floats get truncated, and complex scalars
         # use * for non-finite imaginary part
diff --git a/numpy/_core/tests/test_scalarprint.py b/numpy/_core/tests/test_scalarprint.py
@@ -48,6 +48,17 @@ def check(v):
         check(1e15)
         check(1e16)
 
+    def test_gh_28679(self):
+        # test cutoff to exponent notation for half and single
+        assert_equal(str(np.half(-0.000099)), "-9.9e-05")
+        assert_equal(str(np.half(0.0001)), "0.0001")
+        assert_equal(str(np.half(999)), "999.0")
+        assert_equal(str(np.half(-1000)), "-1e+03")
+        assert_equal(str(np.single(0.000099)), "9.9e-05")
+        assert_equal(str(np.single(-0.000100001)), "-0.000100001")
+        assert_equal(str(np.single(9999999)), "9999999.0")
+        assert_equal(str(np.single(-10000000)), "-1e+07")
+
     def test_dragon4(self):
         # these tests are adapted from Ryan Juckett's dragon4 implementation,
         # see dragon4.c for details.
