✨ Added DIMACS reader to KCNF class.

lib/kcnf.cpp

@@ -115,8 +115,8 @@ KCNF KCNF::generate_random(long n, long c, long k) {
     long long estimated_bytes =
     c * (sizeof(Clause) + k * sizeof(int));
 
-    if (estimated_bytes > 500 * 1024 * 1024) { // 500MB
-        throw std::runtime_error("Estimated memory too large");
+    if (estimated_bytes > 500 * 1024 * 1024) { // 500MB, you may change this line for yourself if you are happy using more memory.
+        throw std::runtime_error("Estimated memory too large.");
     }
 
     auto indices = sample_indices(total, c);
@@ -148,3 +148,65 @@ bool KCNF::write_dimacs(const std::string& filename) const {
 
     return true;
 }
+
+KCNF KCNF::read_dimacs(const std::string& filename) {
+    KCNF f;
+
+    std::ifstream in(filename);
+    if (!in) {
+        throw std::runtime_error("Could not open DIMACS file.");
+    }
+
+    std::string line;
+    long expected_clauses = 0;
+
+    while (std::getline(in, line)) {
+        if (line.empty()) continue;
+
+        if (line[0] == 'c') continue;
+
+        if (line[0] == 'p') {
+            std::istringstream iss(line);
+            std::string tmp, format;
+            iss >> tmp >> format >> f.n >> expected_clauses;
+
+            if (format != "cnf") {
+                throw std::runtime_error("Unsupported DIMACS format.");
+            }
+            continue;
+        }
+
+        std::istringstream iss(line);
+        Clause cl;
+        int lit;
+
+        while (iss >> lit) {
+            if (lit == 0) break;
+            cl.push_back(lit);
+        }
+
+        if (!cl.empty()) {
+            f.clauses.push_back(cl);
+        }
+    }
+
+    if (expected_clauses != 0 && 
+        f.clauses.size() != (size_t)expected_clauses) {
+        std::cerr << "Warning: Clause count mismatch.\n";
+    }
+
+    if (!f.clauses.empty()) {
+        f.k = f.clauses[0].size();
+        
+        // check whether actually k-cnf
+        for (const auto& cl : f.clauses) {
+            if ((long)cl.size() != f.k) {
+                throw std::runtime_error("Input is not a k-CNF formula.");
+            }
+        }
+    } else {
+        f.k = 0;
+    }
+
+    return f;
+}

lib/kcnf.hpp

@@ -14,4 +14,5 @@ public:
     static KCNF generate_random(long n, long c, long k);
 
     bool write_dimacs(const std::string& filename) const;
+    static KCNF read_dimacs(const std::string& filename);
 };