diff --git a/keopscore/keopscore/formulas/maths/ClampInt.py b/keopscore/keopscore/formulas/maths/ClampInt.py
index 0e1f9735..1618e434 100644
--- a/keopscore/keopscore/formulas/maths/ClampInt.py
+++ b/keopscore/keopscore/formulas/maths/ClampInt.py
@@ -27,8 +27,9 @@ class Class(ClampInt_Impl):
             """
 
             string_id = "ClampInt"
+            print_fun = lambda x: f"ClampInt({x},{a},{b})"
 
-            ScalarOpFun = keops_clampint
+            ScalarOpFun = lambda x: keops_clampint(x, a, b)
 
             @staticmethod
             def Derivative(x):
diff --git a/keopscore/keopscore/formulas/maths/DiffClampInt.py b/keopscore/keopscore/formulas/maths/DiffClampInt.py
index 07055552..62346c54 100644
--- a/keopscore/keopscore/formulas/maths/DiffClampInt.py
+++ b/keopscore/keopscore/formulas/maths/DiffClampInt.py
@@ -29,8 +29,9 @@ def __init__(self, a, b):
 
         class Class(DiffClampInt_Impl):
             string_id = "DiffClampInt"
+            print_fun = lambda x: f"DiffClampInt({x},{a},{b})"
 
-            ScalarOpFun = keops_diffclampint
+            ScalarOpFun = lambda x: keops_diffclampint(x, a, b)
 
             def DiffT_fun(self, v, gradin):
                 from keopscore.formulas import Zero
diff --git a/keopscore/keopscore/formulas/maths/Divide.py b/keopscore/keopscore/formulas/maths/Divide.py
index 4bc48be5..bf656bc3 100644
--- a/keopscore/keopscore/formulas/maths/Divide.py
+++ b/keopscore/keopscore/formulas/maths/Divide.py
@@ -3,8 +3,8 @@
 from keopscore.formulas.maths.Scalprod import Scalprod
 from keopscore.formulas.maths.Sum import Sum
 from keopscore.formulas.maths.Square import Square
-from keopscore.formulas.variables.Zero import Zero
-from keopscore.formulas.variables.IntCst import IntCst, IntCst_Impl
+from keopscore.formulas.variables.Zero import Zero_Impl
+from keopscore.formulas.variables.IntCst import IntCst_Impl
 from keopscore.formulas.variables.RatCst import RatCst, RatCst_Impl
 from keopscore.utils.misc_utils import KeOps_Error
 from keopscore.utils.math_functions import keops_div
@@ -43,9 +43,9 @@ def DiffT_fun(self, v, gradin):
 # N.B. The following separate function should theoretically be implemented
 # as a __new__ method of the previous class, but this can generate infinite recursion problems
 def Divide(arg0, arg1):
-    if isinstance(arg0, Zero):
+    if isinstance(arg0, Zero_Impl):
         return Broadcast(arg0, arg1.dim)
-    elif isinstance(arg1, Zero):
+    elif isinstance(arg1, Zero_Impl):
         KeOps_Error("division by zero")
     elif isinstance(arg1, IntCst_Impl):
         return RatCst(1, arg1.val) * arg0
diff --git a/keopscore/keopscore/mapreduce/cpu/CpuReduc.py b/keopscore/keopscore/mapreduce/cpu/CpuReduc.py
index 19d39677..8b09815a 100644
--- a/keopscore/keopscore/mapreduce/cpu/CpuReduc.py
+++ b/keopscore/keopscore/mapreduce/cpu/CpuReduc.py
@@ -1,8 +1,14 @@
 import keopscore
 from keopscore.binders.cpp.Cpu_link_compile import Cpu_link_compile
+from keopscore.utils.meta_toolbox.c_function import c_templated_function
 from keopscore.mapreduce.cpu.CpuAssignZero import CpuAssignZero
 from keopscore.mapreduce.MapReduce import MapReduce
-from keopscore.utils.meta_toolbox import c_include
+from keopscore.utils.meta_toolbox import (
+    c_include,
+    c_variable,
+    c_for,
+    c_return,
+)
 import keopscore
 
 
@@ -34,6 +40,11 @@ def get_code(self):
         table = self.varloader.direct_table(args, i, j)
         sum_scheme = self.sum_scheme
 
+        nx = c_variable("signed long int", "nx")
+        ny = c_variable("signed long int", "ny")
+
+        out = self.out
+
         headers = ["cmath", "stdlib.h"]
         if keopscore.config.config.use_OpenMP:
             headers.append("omp.h")
@@ -41,28 +52,41 @@ def get_code(self):
             headers.append("iostream")
         self.headers += c_include(*headers)
 
-        self.code = f"""
-{self.headers}
-template < typename TYPE > 
-int CpuConv_{self.gencode_filename}(signed long int nx, signed long int ny, TYPE* out, TYPE **{arg.id}) {{
-    #pragma omp parallel for
-    for (signed long int i = 0; i < nx; i++) {{
-        {fout.declare()}
-        {acc.declare()}
-        {sum_scheme.declare_temporary_accumulator()}
-        {red_formula.InitializeReduction(acc)}
-        {sum_scheme.initialize_temporary_accumulator()}
-        for (signed long int j = 0; j < ny; j++) {{
-            {red_formula.formula(fout,table,i,j,tagI)}
-            {sum_scheme.accumulate_result(acc, fout, j)}
-            {sum_scheme.periodic_accumulate_temporary(acc, j)}
-        }}
-        {sum_scheme.final_operation(acc)}
-        {red_formula.FinalizeOutput(acc, outi, i)}
-    }}
-    return 0;
-}}
-                    """
+        code = self.headers + c_templated_function(
+            dtype_out="int",
+            name="CpuConv_" + self.gencode_filename,
+            input_vars=(nx, ny, out, arg),
+            body=(
+                c_for(
+                    decorator="#pragma omp parallel for",
+                    init=i.declare_assign(0),
+                    end=i < nx,
+                    loop=i.plus_plus,
+                    body=(
+                        fout.declare(),
+                        acc.declare(),
+                        sum_scheme.declare_temporary_accumulator(),
+                        red_formula.InitializeReduction(acc),
+                        sum_scheme.initialize_temporary_accumulator(),
+                        c_for(
+                            init=j.declare_assign(0),
+                            end=j < ny,
+                            loop=j.plus_plus,
+                            body=(
+                                red_formula.formula(fout, table, i, j, tagI),
+                                sum_scheme.accumulate_result(acc, fout, j),
+                                sum_scheme.periodic_accumulate_temporary(acc, j),
+                            ),
+                        ),
+                        sum_scheme.final_operation(acc),
+                        red_formula.FinalizeOutput(acc, outi, i),
+                    ),
+                ),
+                c_return(0),
+            ),
+        )
+
+        self.code = str(code)
 
         self.code += f"""
 #include "stdarg.h"
diff --git a/keopscore/keopscore/utils/Tree.py b/keopscore/keopscore/utils/Tree.py
index 5cdce146..8a774d63 100644
--- a/keopscore/keopscore/utils/Tree.py
+++ b/keopscore/keopscore/utils/Tree.py
@@ -46,7 +46,7 @@ def nice_print(self):
             formula_string = formula_string.replace(var_string, v.label)
             if v.ind >= 0:
                 varstrings.append(f"{v.label}={var_string}")
-        string = formula_string + " with " + ", ".join(varstrings)
+        string = formula_string + " with " + "; ".join(varstrings)
         return string
 
     def make_dot(self, filename=None):
diff --git a/keopscore/keopscore/utils/meta_toolbox/c_code.py b/keopscore/keopscore/utils/meta_toolbox/c_code.py
index 654b494f..11fe2d7d 100644
--- a/keopscore/keopscore/utils/meta_toolbox/c_code.py
+++ b/keopscore/keopscore/utils/meta_toolbox/c_code.py
@@ -31,3 +31,6 @@ def c_include(*headers, **kwargs):
 
 def c_define(name, value, **kwargs):
     return c_code(f"#define {name} {value}\n", **kwargs)
+
+
+c_line_break = c_code("\n")
diff --git a/keopscore/keopscore/utils/meta_toolbox/c_expression.py b/keopscore/keopscore/utils/meta_toolbox/c_expression.py
index ed123c43..fa833da4 100644
--- a/keopscore/keopscore/utils/meta_toolbox/c_expression.py
+++ b/keopscore/keopscore/utils/meta_toolbox/c_expression.py
@@ -74,6 +74,10 @@ def __truediv__(self, other):
         python_op = lambda x, y: x / y
         return self.binary_op(other, python_op, "/", "division")
 
+    def equals(self, other):
+        python_op = lambda x, y: x == y
+        return self.binary_op(other, python_op, "==", "comparison", dtype="bool")
+
     def __lt__(self, other):
         python_op = lambda x, y: x < y
         return self.binary_op(other, python_op, "<", "comparison", dtype="bool")
diff --git a/keopscore/keopscore/utils/meta_toolbox/c_function.py b/keopscore/keopscore/utils/meta_toolbox/c_function.py
index ce7cc7de..07050b48 100644
--- a/keopscore/keopscore/utils/meta_toolbox/c_function.py
+++ b/keopscore/keopscore/utils/meta_toolbox/c_function.py
@@ -48,3 +48,20 @@ class cuda_global_kernel(c_function):
 
     def __init__(self, name, input_vars=(), body=c_empty_instruction, **kwargs):
         super().__init__('extern "C" __global__ void', name, input_vars, body, **kwargs)
+
+
+class c_templated_function(c_function):
+
+    def __init__(
+        self,
+        dtype_out,
+        name,
+        input_vars=(),
+        body=c_empty_instruction,
+        typename="TYPE",
+        **kwargs,
+    ):
+        decorator = f"template < typename {typename} >"
+        super().__init__(
+            dtype_out, name, input_vars, body, decorator=decorator, **kwargs
+        )
diff --git a/keopscore/keopscore/utils/meta_toolbox/c_instruction.py b/keopscore/keopscore/utils/meta_toolbox/c_instruction.py
index b69c3636..83638662 100644
--- a/keopscore/keopscore/utils/meta_toolbox/c_instruction.py
+++ b/keopscore/keopscore/utils/meta_toolbox/c_instruction.py
@@ -1,4 +1,5 @@
 from .c_code import c_code
+from .c_expression import py2c
 from .misc import Meta_Toolbox_Error
 
 
@@ -56,5 +57,10 @@ def c_instruction_from_string(string):
         return c_instruction(string, set(), set())
 
 
+def c_return(c_expr):
+    c_expr = py2c(c_expr)
+    return c_instruction_from_string(f"return {c_expr}")
+
+
 def c_comment(string):
     return c_instruction("// " + string, set(), set())
diff --git a/pykeops/pykeops/sandbox/test_lazytensor_clamp.py b/pykeops/pykeops/sandbox/test_lazytensor_clamp.py
index 2d021f3a..2e937b52 100644
--- a/pykeops/pykeops/sandbox/test_lazytensor_clamp.py
+++ b/pykeops/pykeops/sandbox/test_lazytensor_clamp.py
@@ -8,11 +8,11 @@
 
 M, N, D = 1000, 1000, 3
 
-test_grad = True
+test_grad = False
 
 device_id = "cuda:0" if torch.cuda.is_available() else "cpu"
 
-do_warmup = True
+do_warmup = False
 
 x = torch.randn(M, 1, D, requires_grad=test_grad, device=device_id)
 y = torch.randn(1, N, D, device=device_id)