Merge pull request #534 from skirpichev/fix-mpz-__float__-533

Fix mpz/mpq.__float__, add tests
aleaxit · Dec 10, 2024 · 94f455c · 94f455c
2 parents 3609fb4 + f44c19b
commit 94f455c
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Showing 5 changed files with 115 additions and 30 deletions.
diff --git a/src/gmpy2_convert_gmp.c b/src/gmpy2_convert_gmp.c
@@ -164,23 +164,69 @@ GMPy_MPZ_Int_Slot(MPZ_Object *self)
     return GMPy_PyLong_From_MPZ(self, NULL);
 }
 
+static CTXT_Object *
+_get_ieee_context(long bitwidth)
+{
+    assert(bitwidth != 16 || bitwidth%32 == 0);
+
+    CTXT_Object *result = (CTXT_Object*)GMPy_CTXT_New();
+
+    if (!result) {
+        return NULL;
+    }
+    if (bitwidth == 16) {
+        result->ctx.mpfr_prec = 11;
+        result->ctx.emax = 16;
+    }
+    else if (bitwidth == 32) {
+        result->ctx.mpfr_prec = 24;
+        result->ctx.emax = 128;
+    }
+    else if (bitwidth == 64) {
+        result->ctx.mpfr_prec = 53;
+        result->ctx.emax = 1024;
+    }
+    else if (bitwidth == 128) {
+        result->ctx.mpfr_prec = 113;
+        result->ctx.emax = 16384;
+    }
+    else {
+        double bitlog2 = floor((4 * log(bitwidth) / log(2.0)) + 0.5);
+        result->ctx.mpfr_prec = bitwidth - (long)(bitlog2) + 13;
+        result->ctx.emax = 1 << (bitwidth - result->ctx.mpfr_prec - 1);
+    }
+    result->ctx.subnormalize = 1;
+    result->ctx.emin = 4 - result->ctx.emax - result->ctx.mpfr_prec;
+    return (PyObject*)result;
+}
+
 static PyObject *
-GMPy_PyFloat_From_MPZ(MPZ_Object *obj, CTXT_Object *context)
+GMPy_PyFloat_From_MPZ(MPZ_Object *obj, CTXT_Object *unused)
 {
-    double res;
-    mpfr_t temp;
-
-    mpfr_init2(temp, 53);
-    mpfr_set_z(temp, obj->z, MPFR_RNDN);
-    res = mpfr_get_d(temp, MPFR_RNDN);
-    mpfr_clear(temp);
-
-    if (isinf(res)) {
-        OVERFLOW_ERROR("'mpz' too large to convert to float");
+    MPFR_Object *tmp;
+    CTXT_Object *context = _get_ieee_context(64);
+
+    CHECK_CONTEXT(context);
+
+    if (!(tmp = GMPy_MPFR_New(53, context))) {
+        /* LCOV_EXCL_START */
         return NULL;
+        /* LCOV_EXCL_STOP */
     }
 
-    return PyFloat_FromDouble(res);
+    mpfr_clear_flags();
+    tmp->rc = mpfr_set_z(tmp->f, obj->z, MPFR_RNDN);
+    GMPY_MPFR_CHECK_RANGE(tmp, context);
+    GMPY_MPFR_SUBNORMALIZE(tmp, context);
+    GMPY_MPFR_EXCEPTIONS(tmp, context);
+
+    PyObject *res = GMPy_PyFloat_From_MPFR(tmp, context);
+    Py_DECREF(tmp);
+    Py_DECREF(context);
+    if (!res) {
+        OVERFLOW_ERROR("'mpz' too large to convert to float");
+    }
+    return res;
 }
 
 static PyObject *
@@ -799,22 +845,32 @@ GMPy_PyStr_From_MPQ(MPQ_Object *obj, int base, int option, CTXT_Object *context)
 }
 
 static PyObject *
-GMPy_PyFloat_From_MPQ(MPQ_Object *obj, CTXT_Object *context)
+GMPy_PyFloat_From_MPQ(MPQ_Object *obj, CTXT_Object *unused)
 {
-    double res;
-    mpfr_t temp;
-
-    mpfr_init2(temp, 53);
-    mpfr_set_q(temp, obj->q, MPFR_RNDN);
-    res = mpfr_get_d(temp, MPFR_RNDN);
-    mpfr_clear(temp);
-
-    if (isinf(res)) {
-        OVERFLOW_ERROR("'mpq' too large to convert to float");
+    MPFR_Object *tmp;
+    CTXT_Object *context = _get_ieee_context(64);
+
+    CHECK_CONTEXT(context);
+
+    if (!(tmp = GMPy_MPFR_New(53, context))) {
+        /* LCOV_EXCL_START */
         return NULL;
+        /* LCOV_EXCL_STOP */
     }
 
-    return PyFloat_FromDouble(res);
+    mpfr_clear_flags();
+    tmp->rc = mpfr_set_q(tmp->f, obj->q, MPFR_RNDN);
+    GMPY_MPFR_CHECK_RANGE(tmp, context);
+    GMPY_MPFR_SUBNORMALIZE(tmp, context);
+    GMPY_MPFR_EXCEPTIONS(tmp, context);
+
+    PyObject *res = GMPy_PyFloat_From_MPFR(tmp, context);
+    Py_DECREF(tmp);
+    Py_DECREF(context);
+    if (!res) {
+        OVERFLOW_ERROR("'mpq' too large to convert to float");
+    }
+    return res;
 }
 
 static PyObject *

diff --git a/src/gmpy2_convert_mpfr.c b/src/gmpy2_convert_mpfr.c
@@ -769,15 +769,14 @@ GMPy_MPFR_Int_Slot(MPFR_Object *self) {
 static PyObject *
 GMPy_PyFloat_From_MPFR(MPFR_Object *self, CTXT_Object *context)
 {
-    double res;
-    
-    res = mpfr_get_d(self->f, MPFR_RNDN);
+    CHECK_CONTEXT(context);
+
+    double res = mpfr_get_d(self->f, GET_MPFR_ROUND(context));
 
     if (isinf(res)) {
         OVERFLOW_ERROR("'mpfr' too large to convert to float");
         return NULL;
     }
-
     return PyFloat_FromDouble(res);
 }
 

diff --git a/test/test_mpfr.py b/test/test_mpfr.py
@@ -108,9 +108,7 @@ def test_mpfr_conversion():
     assert xmpz(mpfr(5.51)) == xmpz(6)
 
     pytest.raises(OverflowError, lambda: mpq(mpfr('inf')))
-
     pytest.raises(OverflowError, lambda: float(mpfr('inf')))
-
     pytest.raises(OverflowError, lambda: float(mpfr('1e+400')))
 
     assert mpq(mpfr(4.5)) == mpq(9,2)

diff --git a/test/test_mpq.py b/test/test_mpq.py
@@ -1,6 +1,7 @@
 import math
 import numbers
 import pickle
+import platform
 import sys
 from decimal import Decimal
 from fractions import Fraction
@@ -42,6 +43,22 @@ def test_mpq_float():
     assert float(mpq(9, 5)) == 1.8
 
 
+@pytest.mark.skipif(platform.machine() != "x86_64",
+                    reason="XXX: fails in i686 manylinux images")
+@settings(max_examples=10000)
+@given(fractions())
+@example(Fraction(12143, 31517))
+def test_mpq_float_bulk(x):
+    q = mpq(x)
+    try:
+        fx = float(x)
+    except OverflowError:
+        with pytest.raises(OverflowError):
+            float(q)
+    else:
+        assert fx == float(q)
+
+
 def test_mpq_from_Decimal():
     assert mpq(Decimal("5e-3")) == mpq(5, 1000)
     assert mpq(Decimal(1)) == mpq(1)  # issue 327

diff --git a/test/test_mpz.py b/test/test_mpz.py
@@ -506,6 +506,21 @@ def test_mpz_round():
     raises(TypeError, lambda: round(mpz(123456),'a',4))
 
 
+@settings(max_examples=10000)
+@given(integers())
+@example(38732858750156021)
+@example(225188150488381457)
+def test_mpz_float_bulk(n):
+    m = mpz(n)
+    try:
+        fn = float(n)
+    except OverflowError:
+        with raises(OverflowError):
+            float(m)
+    else:
+        assert fn == float(m)
+
+
 def test_mpz_bool():
     assert bool(mpz(100))
     assert not bool(mpz(0))