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Subject [GitHub] [incubator-tvm] sergei-grechanik commented on a change in pull request #5618: [Arith] Inequalities solver
Date Tue, 23 Jun 2020 15:24:38 GMT
```
sergei-grechanik commented on a change in pull request #5618:
URL: https://github.com/apache/incubator-tvm/pull/5618#discussion_r444310282

##########
File path: python/tvm/testing.py
##########
@@ -188,5 +189,96 @@ def assert_prim_expr_equal(lhs, rhs):
raise ValueError("{} and {} are not equal".format(lhs, rhs))

+def check_bool_expr_is_true(bool_expr, vranges, cond=None):
+    """ Check that bool_expr holds given the condition cond
+    for every value of free variables from vranges.
+
+    Parameters
+    ----------
+    bool_expr : tvm.ir.expr.PrimExpr
+        Boolean expression to check
+    vranges: Dict[tvm.tir.expr.Var, tvm.ir.Range]
+        Free variables and their ranges
+    cond: tvm.ir.expr.PrimExpr
+        extra conditions needs to be satisfied.
+    """
+    if cond is not None:
+        bool_expr = tvm.te.any(tvm.tir.Not(cond), bool_expr)
+
+    def _run_expr(expr, vranges):
+        """ Evaluate expr for every value of free variables
+        given by vranges and return the tensor of results.
+        """
+        def _compute_body(*us):
+            vmap = {v: u + r.min for (v, r), u in zip(vranges.items(), us)}
+            return tvm.tir.stmt_functor.substitute(expr, vmap)
+
+        A = tvm.te.compute([r.extent.value for v, r in vranges.items()], _compute_body)
+        args = [tvm.nd.empty(A.shape, A.dtype)]
+        sch = tvm.te.create_schedule(A.op)
+        mod = tvm.build(sch, [A])
+        mod(*args)
+        return args.asnumpy()
+
+    res = _run_expr(bool_expr, vranges)
+    if not np.all(res):
+        indices = list(np.argwhere(res == 0))
+        counterex = [(str(v), i + r.min) for (v, r), i in zip(vranges.items(), indices)]
+        counterex = sorted(counterex, key=lambda x: x)
+        counterex = ", ".join([v + " = " + str(i) for v, i in counterex])
+        ana = tvm.arith.Analyzer()
+        raise AssertionError("Expression {}\nis not true on {}\n"
+                             "Counterexample: {}"
+                             .format(ana.simplify(bool_expr), vranges, counterex))
+
+
+def check_int_constraints_trans_consistency(constraints_trans, vranges=None):
+    """ Check IntConstraintsTransform is a bijective transformation.
+
+    Parameters
+    ----------
+    constraints_trans : arith.IntConstraintsTransform
+        Integer constraints transformation
+    vranges: Dict[tvm.tir.expr.Var, tvm.ir.Range]
+        Free variables and their ranges
+    """
+    if vranges is None:
+        vranges = {}
+
+    def _check_forward(constraints1, constraints2, varmap, backvarmap):
+        ana = tvm.arith.Analyzer()
+        all_vranges = vranges.copy()
+        all_vranges.update({v: r for v, r in constraints1.ranges.items()})
+
+        # Check that the transformation is injective
+        cond_on_vars = tvm.tir.const(1, 'bool')
+        for v in constraints1.variables:
+            # variable mapping is consistent
+            v_back = ana.simplify(tvm.tir.stmt_functor.substitute(varmap[v], backvarmap))
+            cond_on_vars = tvm.te.all(cond_on_vars, v == v_back)
+        # Also we have to check that the new relations are true when old relations are true
+        cond_subst = tvm.tir.stmt_functor.substitute(
+            tvm.te.all(tvm.tir.const(1, 'bool'), *constraints2.relations), backvarmap)
+        # We have to include relations from vranges too
+        for v in constraints2.variables:
+            if v in constraints2.ranges:
+                r = constraints2.ranges[v]
+                range_cond = tvm.te.all(v >= r.min, v < r.min + r.extent)
+                range_cond = tvm.tir.stmt_functor.substitute(range_cond, backvarmap)
+                cond_subst = tvm.te.all(cond_subst, range_cond)
+        cond_subst = ana.simplify(cond_subst)
+        check_bool_expr_is_true(
+            tvm.te.all(cond_subst, cond_on_vars), all_vranges,
+            cond=tvm.te.all(tvm.tir.const(1, 'bool'), *constraints1.relations))
+
+    rels = constraints_trans.dst.relations
+    if len(rels) == 1 and tvm.ir.structural_equal(rels, False):
+        # not solvable, skip

Review comment:
You can check that the original constraints are false for all values of the variables.
I would remove this check completely, I think _check_forward should do what is needed automatically
or with some minor changes.

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