Update docstring, notebook and add test for symbolic costs

qualtran/bloqs/gf_arithmetic/gf2_inverse.ipynb

@@ -65,7 +65,8 @@
     "\n",
     "#### Registers\n",
     " - `x`: Input THRU register of size $m$ that stores elements from $GF(2^m)$.\n",
-    " - `result`: Output RIGHT register of size $m$ that stores $x^{-1}$ from $GF(2^m)$.\n"
+    " - `result`: Output RIGHT register of size $m$ that stores $x^{-1}$ from $GF(2^m)$.\n",
+    " - `junk`: Output RIGHT register of size $m$ and shape ($m - 2$) that stores results from intermediate multiplications.\n"
    ]
   },
   {
@@ -137,8 +138,8 @@
    "outputs": [],
    "source": [
     "from qualtran.drawing import show_bloqs\n",
-    "show_bloqs([gf16_inverse, gf2_inverse_symbolic],\n",
-    "           ['`gf16_inverse`', '`gf2_inverse_symbolic`'])"
+    "show_bloqs([gf16_inverse],\n",
+    "           ['`gf16_inverse`'])"
    ]
   },
   {

qualtran/bloqs/gf_arithmetic/gf2_inverse.py

@@ -34,7 +34,7 @@
 
 if TYPE_CHECKING:
     from qualtran import BloqBuilder, Soquet
-    from qualtran.resource_counting import BloqCountDictT, BloqCountT, SympySymbolAllocator
+    from qualtran.resource_counting import BloqCountDictT, BloqCountT, CostKey, SympySymbolAllocator
     from qualtran.simulation.classical_sim import ClassicalValT
 
 
@@ -71,6 +71,8 @@ class GF2Inverse(Bloq):
     Registers:
         x: Input THRU register of size $m$ that stores elements from $GF(2^m)$.
         result: Output RIGHT register of size $m$ that stores $x^{-1}$ from $GF(2^m)$.
+        junk: Output RIGHT register of size $m$ and shape ($m - 2$) that stores
+            results from intermediate multiplications.
     """
 
     bitsize: SymbolicInt
@@ -94,6 +96,14 @@ def signature(self) -> 'Signature':
     def qgf(self) -> QGF:
         return QGF(characteristic=2, degree=self.bitsize)
 
+    def my_static_costs(self, cost_key: 'CostKey'):
+        from qualtran.resource_counting import QubitCount
+
+        if isinstance(cost_key, QubitCount):
+            return self.signature.n_qubits()
+
+        return NotImplemented
+
     def build_composite_bloq(self, bb: 'BloqBuilder', *, x: 'Soquet') -> Dict[str, 'Soquet']:
         if is_symbolic(self.bitsize):
             raise DecomposeTypeError(f"Cannot decompose symbolic {self}")
@@ -149,9 +159,9 @@ def _gf16_inverse() -> GF2Inverse:
 def _gf2_inverse_symbolic() -> GF2Inverse:
     import sympy
 
-    m = sympy.Symbol('m')
+    m = sympy.Symbol('m', positive=True, integer=True)
     gf2_inverse_symbolic = GF2Inverse(m)
     return gf2_inverse_symbolic
 
 
-_GF2_INVERSE_DOC = BloqDocSpec(bloq_cls=GF2Inverse, examples=(_gf16_inverse, _gf2_inverse_symbolic))
+_GF2_INVERSE_DOC = BloqDocSpec(bloq_cls=GF2Inverse, examples=(_gf16_inverse,))

qualtran/bloqs/gf_arithmetic/gf2_inverse_test.py

@@ -13,13 +13,15 @@
 #  limitations under the License.
 
 import pytest
+import sympy
 from galois import GF
 
 from qualtran.bloqs.gf_arithmetic.gf2_inverse import (
     _gf2_inverse_symbolic,
     _gf16_inverse,
     GF2Inverse,
 )
+from qualtran.resource_counting import get_cost_value, QECGatesCost, QubitCount
 from qualtran.testing import assert_consistent_classical_action
 
 
@@ -31,6 +33,13 @@ def test_gf2_multiplication_symbolic(bloq_autotester):
     bloq_autotester(_gf2_inverse_symbolic)
 
 
+def test_gf2_multiplication_symbolic_toffoli_complexity():
+    bloq = _gf2_inverse_symbolic.make()
+    m = bloq.bitsize
+    assert get_cost_value(bloq, QECGatesCost()).toffoli - m**2 * (m - 2) == 0
+    assert sympy.simplify(get_cost_value(bloq, QubitCount()) - m**2) == 0
+
+
 def test_gf2_multiplication_classical_sim_quick():
     m = 1
     bloq = GF2Inverse(m)