✨ CFE Clocking Scheme (#44)

* ✨ Added the CFE clocking scheme proposed in 'CFE: a convenient, flexible, and efficient clocking scheme for quantum-dot cellular automata' * 🎨 Re-formatted clocking scheme array representation code * 📝 Added CFE clocking to the documentation * ✏️ Fixed typo and CFE source paper [skip ci]
cda-tum · Aug 5, 2022 · 94d3eeb · 94d3eeb
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diff --git a/README.md b/README.md
@@ -124,9 +124,9 @@ Built-in schemes are
 |:--------------------------------------------------------:|:------------------------------------------------------------------------:|:-------------------------------------------------------------------------:|
 | <img src="docs/_static/use.png" alt="USE" height="200"/> |         <img src="docs/_static/res.png" alt="RES" height="200"/>         |       <img src="docs/_static/esp.png" alt="2DDWave" height="200"/>        |
 
-|    [BANCS](https://ieeexplore.ieee.org/document/8533251)     |
-|:------------------------------------------------------------:|
-| <img src="docs/_static/bancs.png" alt="BANCS" height="300"/> |
+|   [CFE](https://ietresearch.onlinelibrary.wiley.com/doi/10.1049/iet-cds.2019.0096)   |    [BANCS](https://ieeexplore.ieee.org/document/8533251)     |
+|:------------------------------------------------------------------------------------:|:------------------------------------------------------------:|
+|               <img src="docs/_static/cfe.png" alt="CFE" height="200"/>               | <img src="docs/_static/bancs.png" alt="BANCS" height="300"/> |
 
 plus the mentioned irregular open clocking that works via a clock map instead of a regular extrapolated cutout.
 

diff --git a/cli/cmd/physical_design/exact.hpp b/cli/cmd/physical_design/exact.hpp
@@ -38,7 +38,7 @@ class exact_command : public command
     {
         add_option("--clk_scheme,-s", clocking,
                    "Clocking scheme to use {OPEN[3|4], COLUMNAR[3|4], ROW[3|4] 2DDWAVE[3|4], 2DDWAVEHEX[3|4], USE, "
-                   "RES, ESP, BANCS}",
+                   "RES, ESP, CFE, BANCS}",
                    true);
         add_option("--upper_bound,-u", ps.upper_bound, "Number of FCN gate tiles to use at maximum");
         add_option("--fixed_size,-f", ps.fixed_size, "Execute only one iteration with the given number of tiles");

diff --git a/cli/cmd/physical_design/onepass.hpp b/cli/cmd/physical_design/onepass.hpp
@@ -48,7 +48,8 @@ class onepass_command : public command
                        "resulting from this approach might be desynchronized. I/Os are always located at the "
                        "layout's borders.")
     {
-        add_option("--clk_scheme,-s", clocking, "Clocking scheme to use {2DDWAVE[3|4], USE, RES, ESP, BANCS}", true);
+        add_option("--clk_scheme,-s", clocking, "Clocking scheme to use {2DDWAVE[3|4], USE, RES, ESP, CFE, BANCS}",
+                   true);
         add_option("--upper_bound,-u", ps.upper_bound, "Number of FCN gate tiles to use at maximum");
         add_option("--fixed_size,-f", ps.fixed_size, "Execute only one iteration with the given number of tiles");
         add_option("--timeout,-t", ps.timeout, "Timeout in seconds");

diff --git a/docs/_static/cfe.png b/docs/_static/cfe.png
diff --git a/docs/layouts/clocking_scheme.rst b/docs/layouts/clocking_scheme.rst
@@ -72,6 +72,14 @@ ESP
 
 .. doxygenfunction:: fiction::esp_clocking
 
+CFE
+###
+
+.. figure:: /_static/cfe.png
+   :width: 200
+
+.. doxygenfunction:: fiction::cfe_clocking
+
 BANCS
 #####
 

diff --git a/include/fiction/layouts/clocking_scheme.hpp b/include/fiction/layouts/clocking_scheme.hpp
@@ -158,6 +158,7 @@ static constexpr const char* twoddwave_hex = "2DDWAVEHEX";
 static constexpr const char* use           = "USE";
 static constexpr const char* res           = "RES";
 static constexpr const char* esp           = "ESP";
+static constexpr const char* cfe           = "CFE";
 static constexpr const char* bancs         = "BANCS";
 }  // namespace clock_name
 
@@ -349,11 +350,23 @@ static auto twoddwave_clocking(const num_clks& n = num_clks::FOUR) noexcept
 template <typename Lyt>
 static auto twoddwave_hex_clocking(const num_clks& n = num_clks::FOUR) noexcept
 {
+    // clang-format off
+
     static constexpr std::array<std::array<typename clocking_scheme<clock_zone<Lyt>>::clock_number, 3u>, 6u>
-        odd_3_cutout{{{{0, 1, 2}}, {{1, 2, 0}}, {{1, 2, 0}}, {{2, 0, 1}}, {{2, 0, 1}}, {{0, 1, 2}}}};
+        odd_3_cutout{{{{0, 1, 2}},
+                      {{1, 2, 0}},
+                      {{1, 2, 0}},
+                      {{2, 0, 1}},
+                      {{2, 0, 1}},
+                      {{0, 1, 2}}}};
 
     static constexpr std::array<std::array<typename clocking_scheme<clock_zone<Lyt>>::clock_number, 3u>, 6u>
-        even_3_cutout{{{{0, 1, 2}}, {{0, 1, 2}}, {{1, 2, 0}}, {{1, 2, 0}}, {{2, 0, 1}}, {{2, 0, 1}}}};
+        even_3_cutout{{{{0, 1, 2}},
+                       {{0, 1, 2}},
+                       {{1, 2, 0}},
+                       {{1, 2, 0}},
+                       {{2, 0, 1}},
+                       {{2, 0, 1}}}};
 
     static constexpr std::array<std::array<typename clocking_scheme<clock_zone<Lyt>>::clock_number, 4u>, 8u>
         odd_4_cutout{{{{0, 1, 2, 3}},
@@ -375,6 +388,8 @@ static auto twoddwave_hex_clocking(const num_clks& n = num_clks::FOUR) noexcept
                        {{3, 0, 1, 2}},
                        {{3, 0, 1, 2}}}};
 
+    // clang-format on
+
     static const typename clocking_scheme<clock_zone<Lyt>>::clock_function odd_row_twoddwave_hex_3_clock_function =
         [](const clock_zone<Lyt>& cz) noexcept { return odd_3_cutout[cz.y % 6ul][cz.x % 3ul]; };
 
@@ -516,16 +531,23 @@ static auto twoddwave_hex_clocking(const num_clks& n = num_clks::FOUR) noexcept
 template <typename Lyt>
 static auto use_clocking() noexcept
 {
+    // clang-format off
+
     static const typename clocking_scheme<clock_zone<Lyt>>::clock_function use_clock_function =
         [](const clock_zone<Lyt>& cz) noexcept
     {
         constexpr std::array<std::array<typename clocking_scheme<clock_zone<Lyt>>::clock_number, 4u>, 4u> cutout{
-            {{{0, 1, 2, 3}}, {{3, 2, 1, 0}}, {{2, 3, 0, 1}}, {{1, 0, 3, 2}}}};
+            {{{0, 1, 2, 3}},
+             {{3, 2, 1, 0}},
+             {{2, 3, 0, 1}},
+             {{1, 0, 3, 2}}}};
 
         return cutout[cz.y % 4ul][cz.x % 4ul];
     };
 
     return clocking_scheme{clock_name::use, use_clock_function, std::min(Lyt::max_fanin_size, 2u), 2u, 4u, true};
+
+    // clang-format on
 }
 /**
  * Returns the RES clocking as defined in "An efficient clocking scheme for quantum-dot cellular automata" by
@@ -538,16 +560,23 @@ static auto use_clocking() noexcept
 template <typename Lyt>
 static auto res_clocking() noexcept
 {
+    // clang-format off
+
     static const typename clocking_scheme<clock_zone<Lyt>>::clock_function res_clock_function =
         [](const clock_zone<Lyt>& cz) noexcept
     {
         constexpr std::array<std::array<typename clocking_scheme<clock_zone<Lyt>>::clock_number, 4u>, 4u> cutout{
-            {{{3, 0, 1, 2}}, {{0, 1, 0, 3}}, {{1, 2, 3, 0}}, {{0, 3, 2, 1}}}};
+            {{{3, 0, 1, 2}},
+             {{0, 1, 0, 3}},
+             {{1, 2, 3, 0}},
+             {{0, 3, 2, 1}}}};
 
         return cutout[cz.y % 4ul][cz.x % 4ul];
     };
 
     return clocking_scheme{clock_name::res, res_clock_function, std::min(Lyt::max_fanin_size, 3u), 3u, 4u, true};
+
+    // clang-format on
 }
 /**
  * Returns the ESP (Zig-Zag) clocking as defined in "Regular Clocking based Emerging Technique in QCA Targeting Low
@@ -560,16 +589,52 @@ static auto res_clocking() noexcept
 template <typename Lyt>
 static auto esp_clocking() noexcept
 {
+    // clang-format off
+
     static const typename clocking_scheme<clock_zone<Lyt>>::clock_function esp_clock_function =
         [](const clock_zone<Lyt>& cz) noexcept
     {
         constexpr std::array<std::array<typename clocking_scheme<clock_zone<Lyt>>::clock_number, 4u>, 4u> cutout{
-            {{{3, 0, 1, 2}}, {{0, 1, 2, 3}}, {{1, 2, 3, 0}}, {{0, 3, 2, 1}}}};
+            {{{3, 0, 1, 2}},
+             {{0, 1, 2, 3}},
+             {{1, 2, 3, 0}},
+             {{0, 3, 2, 1}}}};
 
         return cutout[cz.y % 4ul][cz.x % 4ul];
     };
 
     return clocking_scheme{clock_name::esp, esp_clock_function, std::min(Lyt::max_fanin_size, 3u), 3u, 4u, true};
+
+    // clang-format on
+}
+/**
+ * Returns the CFE clocking as defined in "CFE: a convenient, flexible, and efficient clocking scheme for quantum-dot
+ * cellular automata" by Feifei Deng, Guang-Jun Xie, Xin Cheng, Zhang Zhang, and Yongqiang Zhang in IET Circuits,
+ * Devices & Systems 2020.
+ *
+ * @tparam Lyt Clocked layout type.
+ * @return CFE clocking scheme.
+ */
+template <typename Lyt>
+static auto cfe_clocking() noexcept
+{
+    // clang-format off
+
+    static const typename clocking_scheme<clock_zone<Lyt>>::clock_function cfe_clock_function =
+        [](const clock_zone<Lyt>& cz) noexcept
+    {
+        constexpr std::array<std::array<typename clocking_scheme<clock_zone<Lyt>>::clock_number, 4u>, 4u> cutout{
+            {{{0, 1, 0, 1}},
+             {{3, 2, 3, 2}},
+             {{0, 1, 0, 1}},
+             {{3, 2, 3, 2}}}};
+
+        return cutout[cz.y % 4ul][cz.x % 4ul];
+    };
+
+    return clocking_scheme{clock_name::cfe, cfe_clock_function, std::min(Lyt::max_fanin_size, 3u), 3u, 4u, true};
+
+    // clang-format on
 }
 /**
  * Returns the BANCS clocking as defined in "BANCS: Bidirectional Alternating Nanomagnetic Clocking Scheme" by
@@ -581,16 +646,25 @@ static auto esp_clocking() noexcept
 template <typename Lyt>
 static auto bancs_clocking() noexcept
 {
+    // clang-format off
+
     static const typename clocking_scheme<clock_zone<Lyt>>::clock_function bancs_clock_function =
         [](const clock_zone<Lyt>& cz) noexcept
     {
         constexpr std::array<std::array<typename clocking_scheme<clock_zone<Lyt>>::clock_number, 3u>, 6u> cutout{
-            {{{0, 1, 2}}, {{2, 1, 0}}, {{2, 0, 1}}, {{1, 0, 2}}, {{1, 2, 0}}, {{0, 2, 1}}}};
+            {{{0, 1, 2}},
+             {{2, 1, 0}},
+             {{2, 0, 1}},
+             {{1, 0, 2}},
+             {{1, 2, 0}},
+             {{0, 2, 1}}}};
 
         return cutout[cz.y % 6ul][cz.x % 3ul];
     };
 
     return clocking_scheme{clock_name::bancs, bancs_clock_function, std::min(Lyt::max_fanin_size, 2u), 2u, 3u, true};
+
+    // clang-format on
 }
 /**
  * Returns a smart pointer to the given scheme.
@@ -655,6 +729,7 @@ std::optional<clocking_scheme<clock_zone<Lyt>>> get_clocking_scheme(const std::s
         {clock_name::use, use_clocking<Lyt>()},
         {clock_name::res, res_clocking<Lyt>()},
         {clock_name::esp, esp_clocking<Lyt>()},
+        {clock_name::cfe, cfe_clocking<Lyt>()},
         {clock_name::bancs, bancs_clocking<Lyt>()}};
 
     auto upper_name = name;

diff --git a/test/algorithms/physical_design/exact.cpp b/test/algorithms/physical_design/exact.cpp
@@ -84,6 +84,22 @@ exact_physical_design_params<Lyt>&& res(exact_physical_design_params<Lyt>&& ps)
     return std::move(ps);
 }
 
+template <typename Lyt>
+exact_physical_design_params<Lyt>&& esp(exact_physical_design_params<Lyt>&& ps) noexcept
+{
+    ps.scheme = std::make_shared<clocking_scheme<coordinate<Lyt>>>(esp_clocking<Lyt>());
+
+    return std::move(ps);
+}
+
+template <typename Lyt>
+exact_physical_design_params<Lyt>&& cfe(exact_physical_design_params<Lyt>&& ps) noexcept
+{
+    ps.scheme = std::make_shared<clocking_scheme<coordinate<Lyt>>>(cfe_clocking<Lyt>());
+
+    return std::move(ps);
+}
+
 template <typename Lyt>
 exact_physical_design_params<Lyt>&& crossings(exact_physical_design_params<Lyt>&& ps) noexcept
 {
@@ -279,6 +295,16 @@ TEST_CASE("Exact Cartesian physical design", "[exact]")
         check_with_gate_library<qca_cell_clk_lyt, qca_one_library>(
             blueprints::and_or_network<mockturtle::mig_network>(), res(crossings(configuration<cart_gate_clk_lyt>())));
     }
+    SECTION("ESP clocking")
+    {
+        check_with_gate_library<qca_cell_clk_lyt, qca_one_library>(
+            blueprints::and_or_network<mockturtle::mig_network>(), esp(crossings(configuration<cart_gate_clk_lyt>())));
+    }
+    SECTION("CFE clocking")
+    {
+        check_with_gate_library<qca_cell_clk_lyt, qca_one_library>(
+            blueprints::and_or_network<mockturtle::mig_network>(), cfe(crossings(configuration<cart_gate_clk_lyt>())));
+    }
     SECTION("Border I/O")
     {
         check_with_gate_library<qca_cell_clk_lyt, qca_one_library>(

diff --git a/test/layouts/clocking_scheme.cpp b/test/layouts/clocking_scheme.cpp
@@ -1617,6 +1617,86 @@ TEST_CASE("4-phase RES", "[clocking-scheme]")
     CHECK(res4({3 + 4, 3 + 4}) == 1);
 }
 
+TEST_CASE("4-phase CFE", "[clocking-scheme]")
+{
+    using clk_lyt = clocked_layout<cartesian_layout<offset::ucoord_t>>;
+
+    const auto cfe4 = cfe_clocking<clk_lyt>();
+
+    CHECK(cfe4.num_clocks == 4u);
+    CHECK(cfe4.max_in_degree == 3u);
+    CHECK(cfe4.max_out_degree == 3u);
+    CHECK(cfe4.is_regular());
+
+    CHECK(cfe4({0, 0}) == 0);
+    CHECK(cfe4({0, 1}) == 3);
+    CHECK(cfe4({0, 2}) == 0);
+    CHECK(cfe4({0, 3}) == 3);
+    CHECK(cfe4({1, 0}) == 1);
+    CHECK(cfe4({1, 1}) == 2);
+    CHECK(cfe4({1, 2}) == 1);
+    CHECK(cfe4({1, 3}) == 2);
+    CHECK(cfe4({2, 0}) == 0);
+    CHECK(cfe4({2, 1}) == 3);
+    CHECK(cfe4({2, 2}) == 0);
+    CHECK(cfe4({2, 3}) == 3);
+    CHECK(cfe4({3, 0}) == 1);
+    CHECK(cfe4({3, 1}) == 2);
+    CHECK(cfe4({3, 2}) == 1);
+    CHECK(cfe4({3, 3}) == 2);
+
+    CHECK(cfe4({0 + 4, 0}) == 0);
+    CHECK(cfe4({0 + 4, 1}) == 3);
+    CHECK(cfe4({0 + 4, 2}) == 0);
+    CHECK(cfe4({0 + 4, 3}) == 3);
+    CHECK(cfe4({1 + 4, 0}) == 1);
+    CHECK(cfe4({1 + 4, 1}) == 2);
+    CHECK(cfe4({1 + 4, 2}) == 1);
+    CHECK(cfe4({1 + 4, 3}) == 2);
+    CHECK(cfe4({2 + 4, 0}) == 0);
+    CHECK(cfe4({2 + 4, 1}) == 3);
+    CHECK(cfe4({2 + 4, 2}) == 0);
+    CHECK(cfe4({2 + 4, 3}) == 3);
+    CHECK(cfe4({3 + 4, 0}) == 1);
+    CHECK(cfe4({3 + 4, 1}) == 2);
+    CHECK(cfe4({3 + 4, 2}) == 1);
+    CHECK(cfe4({3 + 4, 3}) == 2);
+
+    CHECK(cfe4({0, 0 + 4}) == 0);
+    CHECK(cfe4({0, 1 + 4}) == 3);
+    CHECK(cfe4({0, 2 + 4}) == 0);
+    CHECK(cfe4({0, 3 + 4}) == 3);
+    CHECK(cfe4({1, 0 + 4}) == 1);
+    CHECK(cfe4({1, 1 + 4}) == 2);
+    CHECK(cfe4({1, 2 + 4}) == 1);
+    CHECK(cfe4({1, 3 + 4}) == 2);
+    CHECK(cfe4({2, 0 + 4}) == 0);
+    CHECK(cfe4({2, 1 + 4}) == 3);
+    CHECK(cfe4({2, 2 + 4}) == 0);
+    CHECK(cfe4({2, 3 + 4}) == 3);
+    CHECK(cfe4({3, 0 + 4}) == 1);
+    CHECK(cfe4({3, 1 + 4}) == 2);
+    CHECK(cfe4({3, 2 + 4}) == 1);
+    CHECK(cfe4({3, 3 + 4}) == 2);
+
+    CHECK(cfe4({0 + 4, 0 + 4}) == 0);
+    CHECK(cfe4({0 + 4, 1 + 4}) == 3);
+    CHECK(cfe4({0 + 4, 2 + 4}) == 0);
+    CHECK(cfe4({0 + 4, 3 + 4}) == 3);
+    CHECK(cfe4({1 + 4, 0 + 4}) == 1);
+    CHECK(cfe4({1 + 4, 1 + 4}) == 2);
+    CHECK(cfe4({1 + 4, 2 + 4}) == 1);
+    CHECK(cfe4({1 + 4, 3 + 4}) == 2);
+    CHECK(cfe4({2 + 4, 0 + 4}) == 0);
+    CHECK(cfe4({2 + 4, 1 + 4}) == 3);
+    CHECK(cfe4({2 + 4, 2 + 4}) == 0);
+    CHECK(cfe4({2 + 4, 3 + 4}) == 3);
+    CHECK(cfe4({3 + 4, 0 + 4}) == 1);
+    CHECK(cfe4({3 + 4, 1 + 4}) == 2);
+    CHECK(cfe4({3 + 4, 2 + 4}) == 1);
+    CHECK(cfe4({3 + 4, 3 + 4}) == 2);
+}
+
 TEST_CASE("3-phase BANCS", "[clocking-scheme]")
 {
     using clk_lyt = clocked_layout<cartesian_layout<offset::ucoord_t>>;
@@ -1847,6 +1927,7 @@ TEST_CASE("Clocking lookup", "[clocking-scheme]")
     check({"use", "USE", "uSe", "UsE"}, clock_name::use);
     check({"res", "RES", "rEs", "ReS"}, clock_name::res);
     check({"esp", "ESP", "eSp", "EsP"}, clock_name::esp);
+    check({"cfe", "CFE", "cFe", "CfE"}, clock_name::cfe);
     check({"bancs", "BANCS", "BaNCs", "banCS"}, clock_name::bancs);
 
     CHECK(!get_clocking_scheme<clk_lyt>("").has_value());
@@ -1857,6 +1938,7 @@ TEST_CASE("Clocking lookup", "[clocking-scheme]")
     CHECK(!get_clocking_scheme<clk_lyt>("SUE").has_value());
     CHECK(!get_clocking_scheme<clk_lyt>("ERS").has_value());
     CHECK(!get_clocking_scheme<clk_lyt>("EPS").has_value());
+    CHECK(!get_clocking_scheme<clk_lyt>("CEF").has_value());
     CHECK(!get_clocking_scheme<clk_lyt>("BNCS").has_value());
 }
 
@@ -1872,6 +1954,7 @@ TEST_CASE("Linear schemes", "[clocking-scheme]")
     CHECK(!is_linear_scheme<clk_lyt>(*get_clocking_scheme<clk_lyt>(clock_name::open)));
     CHECK(!is_linear_scheme<clk_lyt>(*get_clocking_scheme<clk_lyt>(clock_name::use)));
     CHECK(!is_linear_scheme<clk_lyt>(*get_clocking_scheme<clk_lyt>(clock_name::res)));
-    CHECK(!is_linear_scheme<clk_lyt>(*get_clocking_scheme<clk_lyt>(clock_name::bancs)));
     CHECK(!is_linear_scheme<clk_lyt>(*get_clocking_scheme<clk_lyt>(clock_name::esp)));
+    CHECK(!is_linear_scheme<clk_lyt>(*get_clocking_scheme<clk_lyt>(clock_name::cfe)));
+    CHECK(!is_linear_scheme<clk_lyt>(*get_clocking_scheme<clk_lyt>(clock_name::bancs)));
 }