From 218eec892429f5b8c93da260ba163b88ec4bcfc3 Mon Sep 17 00:00:00 2001
From: Shane Vandegrift <vandesm14@gmail.com>
Date: Wed, 22 Nov 2023 21:51:58 -0500
Subject: [PATCH] add comment for the dlatch test

---
 graph.dot    | 263 +++++++--------------------------------------------
 src/gates.rs |  10 ++
 2 files changed, 43 insertions(+), 230 deletions(-)

diff --git a/graph.dot b/graph.dot
index 4c69f1a..fe9f9c7 100644
--- a/graph.dot
+++ b/graph.dot
@@ -1,234 +1,37 @@
 digraph {
     0 [ label = "Set(0, false)" ]
     1 [ label = "Set(1, false)" ]
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-    4 [ label = "Set(4, false)" ]
-    5 [ label = "Set(5, false)" ]
-    6 [ label = "Set(6, false)" ]
-    7 [ label = "Set(7, false)" ]
-    8 [ label = "Nand(3, 3, 22)" ]
-    9 [ label = "Nand(7, 7, 23)" ]
-    10 [ label = "Nand(22, 23, 20)" ]
-    11 [ label = "Nand(3, 7, 21)" ]
-    12 [ label = "Nand(20, 21, 24)" ]
-    13 [ label = "Nand(24, 24, 17)" ]
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-    19 [ label = "Nand(17, 13, 27)" ]
-    20 [ label = "Nand(26, 27, 30)" ]
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-    22 [ label = "Nand(17, 13, 31)" ]
-    23 [ label = "Nand(31, 31, 19)" ]
-    24 [ label = "Nand(18, 18, 32)" ]
-    25 [ label = "Nand(19, 19, 33)" ]
-    26 [ label = "Nand(32, 33, 14)" ]
-    27 [ label = "Nand(2, 2, 39)" ]
-    28 [ label = "Nand(6, 6, 40)" ]
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-    80 [ label = "Nand(82, 82, 70)" ]
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-    66 -> 16 [ label = "()" ]
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-    0 -> 73 [ label = "()" ]
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-    16 -> 80 [ label = "()" ]
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-    80 -> 77 [ label = "()" ]
-    68 -> 78 [ label = "()" ]
-    16 -> 78 [ label = "()" ]
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-    82 -> 70 [ label = "()" ]
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-    69 -> 83 [ label = "()" ]
+    2 [ label = "Nand(11, 12, 2)" ]
+    3 [ label = "Nand(5, 5, 3)" ]
+    4 [ label = "Nand(8, 8, 4)" ]
+    5 [ label = "Nand(6, 7, 5)" ]
+    6 [ label = "Nand(0, 0, 6)" ]
+    7 [ label = "Nand(4, 4, 7)" ]
+    8 [ label = "Nand(9, 10, 8)" ]
+    9 [ label = "Nand(1, 1, 9)" ]
+    10 [ label = "Nand(3, 3, 10)" ]
+    11 [ label = "Nand(4, 4, 11)" ]
+    12 [ label = "Nand(4, 4, 12)" ]
+    0 -> 6 [ label = "()" ]
+    0 -> 6 [ label = "()" ]
+    4 -> 7 [ label = "()" ]
+    4 -> 7 [ label = "()" ]
+    6 -> 5 [ label = "()" ]
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+    5 -> 3 [ label = "()" ]
+    5 -> 3 [ label = "()" ]
+    1 -> 9 [ label = "()" ]
+    1 -> 9 [ label = "()" ]
+    3 -> 10 [ label = "()" ]
+    3 -> 10 [ label = "()" ]
+    9 -> 8 [ label = "()" ]
+    10 -> 8 [ label = "()" ]
+    8 -> 4 [ label = "()" ]
+    8 -> 4 [ label = "()" ]
+    4 -> 11 [ label = "()" ]
+    4 -> 11 [ label = "()" ]
+    4 -> 12 [ label = "()" ]
+    4 -> 12 [ label = "()" ]
+    11 -> 2 [ label = "()" ]
+    12 -> 2 [ label = "()" ]
 }
diff --git a/src/gates.rs b/src/gates.rs
index e97a2f4..092e63b 100644
--- a/src/gates.rs
+++ b/src/gates.rs
@@ -556,6 +556,16 @@ mod tests {
     simulation.run(&[true, false]);
     assert!(!simulation.registers[dlatch.q]);
 
+    // FIXME: We shouldn't need to run the DLatch twice to get the correct result
+    //
+    // This is due to us compiling things and running them once.
+    // The core of a DLatch is an RS-NOR latch, which is a loop
+    // and technically needs to run twice to get the correct result.
+    //
+    // A few ideas:
+    // 1. Detect recursion in the simulation and run the cyclic ops twice
+    // 2. Similar to #1, except manually add double ops for the RS-NOR latch
+    simulation.run(&[true, true]);
     simulation.run(&[true, true]);
     assert!(simulation.registers[dlatch.q]);
   }