WIP: add Vector inner and outer products.

I think these methods are worth adding to the main API.
The way in which we do this is SuiteSparse-specific, and we can add recipes
for other implementations if/when that time comes.

Note that `semiring(w @ v)` is sugar for `w.inner(v)`.

TODO:
- [ ] document
- [ ] test
- [ ] allow `v.outer` to accept a `BinaryOp`, `Monoid`, or `Semiring`

xref: DrTimothyAldenDavis/GraphBLAS#57

grblas/base.py

@@ -388,8 +388,16 @@ def _update(self, delayed, mask=None, accum=None, replace=False, input_mask=None
             output_replace=replace,
         )
         if self._is_scalar:
-            args = [_Pointer(self), accum]
-            cfunc_name = delayed.cfunc_name.format(output_dtype=self.dtype)
+            is_fake_scalar = delayed.method_name == "inner"
+            if is_fake_scalar:
+                from .vector import Vector
+
+                fake_self = Vector.new(self.dtype, size=1)
+                args = [fake_self, mask, accum]
+                cfunc_name = delayed.cfunc_name
+            else:
+                args = [_Pointer(self), accum]
+                cfunc_name = delayed.cfunc_name.format(output_dtype=self.dtype)
         else:
             args = [self, mask, accum]
             cfunc_name = delayed.cfunc_name
@@ -400,6 +408,8 @@ def _update(self, delayed, mask=None, accum=None, replace=False, input_mask=None
         # Make the GraphBLAS call
         call(cfunc_name, args)
         if self._is_scalar:
+            if is_fake_scalar:
+                self.value = fake_self[0].value
             self._is_empty = False
 
     @property

grblas/expr.py

@@ -471,6 +471,14 @@ def ncols(self):
         return self._ncols
 
 
+class ScalarMatMulExpr(InfixExprBase):
+    __slots__ = ()
+    method_name = "inner"
+    output_type = None  # ScalarExpression
+    _infix = "@"
+    _example_op = "plus_times"
+
+
 def _ewise_infix_expr(left, right, *, method, within):
     from .vector import Vector
     from .matrix import Matrix, TransposedMatrix
@@ -518,6 +526,8 @@ def _matmul_infix_expr(left, right, *, within):
     if left_type is Vector:
         if right_type is Matrix or right_type is TransposedMatrix:
             method = "vxm"
+        elif right_type is Vector:
+            method = "inner"
         else:
             left._expect_type(
                 right,
@@ -562,4 +572,6 @@ def _matmul_infix_expr(left, right, *, within):
     expr = getattr(left, method)(right, any_pair[bool])
     if expr.output_type is Vector:
         return VectorMatMulExpr(left, right, method_name=method, size=expr._size)
-    return MatrixMatMulExpr(left, right, nrows=expr.nrows, ncols=expr.ncols)
+    elif expr.output_type is Matrix:
+        return MatrixMatMulExpr(left, right, nrows=expr.nrows, ncols=expr.ncols)
+    return ScalarMatMulExpr(left, right)

grblas/vector.py

@@ -511,6 +511,41 @@ def reduce(self, op=monoid.plus):
             op=op,  # to be determined later
         )
 
+    # Unofficial methods
+    def inner(self, other, op=semiring.plus_times):
+        method_name = "inner"
+        self._expect_type(other, Vector, within=method_name, argname="other")
+        op = get_typed_op(op, self.dtype, other.dtype)
+        self._expect_op(op, "Semiring", within=method_name, argname="op")
+        expr = ScalarExpression(
+            method_name,
+            "GrB_vxm",
+            [self, _VectorAsMatrix(other)],
+            op=op,
+            # bt=other._is_transposed,
+        )
+        if self._size != other._size:
+            expr.new(name="")  # incompatible shape; raise now
+        return expr
+
+    def outer(self, other, op=semiring.plus_times):
+        from .matrix import MatrixExpression
+
+        method_name = "outer"
+        self._expect_type(other, Vector, within=method_name, argname="other")
+        op = get_typed_op(op, self.dtype, other.dtype)
+        self._expect_op(op, "Semiring", within=method_name, argname="op")
+        expr = MatrixExpression(
+            method_name,
+            "GrB_mxm",
+            [_VectorAsMatrix(self), _VectorAsMatrix(other)],
+            op=op,
+            nrows=self._size,
+            ncols=other._size,
+            bt=True,
+        )
+        return expr
+
     ##################################
     # Extract and Assign index methods
     ##################################
@@ -702,6 +737,22 @@ def size(self):
         return self._size
 
 
+class _VectorAsMatrix:
+    __slots__ = "vector"
+
+    def __init__(self, vector):
+        self.vector = vector
+
+    @property
+    def _carg(self):
+        # SS, SuiteSparse-specific: casting Vector to Matrix
+        return ffi.cast("GrB_Matrix*", self.vector.gb_obj)[0]
+
+    @property
+    def name(self):
+        return f"(GrB_Matrix){self.vector.name}"
+
+
 expr.VectorEwiseAddExpr.output_type = VectorExpression
 expr.VectorEwiseMultExpr.output_type = VectorExpression
 expr.VectorMatMulExpr.output_type = VectorExpression