Fit fibonacci_fast.cpp to contributing guidelines

Author: setbit123

math/fibonacci_large.cpp

@@ -4,22 +4,27 @@
  * input argument. Uses custom build arbitrary integers library
  * to perform additions and other operations.
  *
+ * @details
  * Took 0.608246 seconds to compute 50,000^th Fibonacci
  * number that contains 10450 digits!
  *
- * \author [Krishna Vedala](https://github.com/kvedala)
+ * @author [Krishna Vedala](https://github.com/kvedala)
  * @see fibonacci.cpp, fibonacci_fast.cpp, string_fibonacci.cpp
  */
 
-#include <cinttypes>
-#include <ctime>
-#include <iostream>
+#include <cinttypes>          /// for uint64_t
+#include <ctime>              /// for clock_t, std::clock, CLOCKS_PER_SEC
+#include <iostream>           /// for IO operations
+#include <stdexcept>          /// for std::invalid_argument
+#include <cassert>            /// for assert
 
-#include "./large_number.h"
+#include "./large_number.h"   /// for large_number class and related functions
 
-/** Compute fibonacci numbers using the relation
- * \f[f(n)=f(n-1)+f(n-2)\f]
- * and returns the result as a large_number type.
+/**
+ * @brief Function to compute the n-th Fibonacci number.
+ * @details \f[f(n)=f(n-1)+f(n-2)\f]
+ * @param n The position in the Fibonacci sequence.
+ * @return The n-th Fibonacci number.
  */
 large_number fib(uint64_t n) {
     large_number f0(1);
@@ -35,51 +40,53 @@ large_number fib(uint64_t n) {
     return f1;
 }
 
-int main(int argc, char *argv[]) {
-    uint64_t N;
-    if (argc == 2) {
-        N = strtoull(argv[1], NULL, 10);
-    } else {
-        std::cout << "Enter N: ";
-        std::cin >> N;
-    }
-
-    clock_t start_time = std::clock();
-    large_number result = fib(N);
-    clock_t end_time = std::clock();
-    double time_taken = static_cast<double>(end_time - start_time) /
-                        static_cast<double>(CLOCKS_PER_SEC);
-
-    std::cout << std::endl
-              << N << "^th Fibonacci number: " << result << std::endl
-              << "Number of digits: " << result.num_digits() << std::endl
-              << "Time taken: " << std::scientific << time_taken << " s"
-              << std::endl;
+/**
+ * @brief Test function to validate the fib function.
+ * @details This function tests the fib function by comparing its result for a
+ * specific input (5000) with a precomputed expected result.
+ */
+void test() {
+    uint64_t N = 5000;
+    large_number expected_result(
+        "387896845438832563370191630832590531208212771464624510616059721489"
+        "555013904403709701082291646221066947929345285888297381348310200895"
+        "498294036143015691147893836421656394410691021450563413370655865623"
+        "825465670071252592990385493381392883637834751890876297071203333705"
+        "292310769300851809384980180384781399674888176555465378829164426891"
+        "298038461377896902150229308247566634622492307188332480328037503913"
+        "035290330450584270114763524227021093463769910400671417488329842289"
+        "149127310405432875329804427367682297724498774987455569190770388063"
+        "704683279481135897373999311010621930814901857081539785437919530561"
+        "751076105307568878376603366735544525884488624161921055345749367589"
+        "784902798823435102359984466393485325641195222185956306047536464547"
+        "076033090242080638258492915645287629157575914234380914230291749108"
+        "898415520985443248659407979357131684169286803954530954538869811466"
+        "508206686289742063932343848846524098874239587380197699382031717420"
+        "893226546887936400263079778005875912967138963421425257911687275560"
+        "0360311370547754724604639987588046985178408674382863125");
 
-    N = 5000;
-    if (fib(N) ==
-        large_number(
-            "387896845438832563370191630832590531208212771464624510616059721489"
-            "555013904403709701082291646221066947929345285888297381348310200895"
-            "498294036143015691147893836421656394410691021450563413370655865623"
-            "825465670071252592990385493381392883637834751890876297071203333705"
-            "292310769300851809384980180384781399674888176555465378829164426891"
-            "298038461377896902150229308247566634622492307188332480328037503913"
-            "035290330450584270114763524227021093463769910400671417488329842289"
-            "149127310405432875329804427367682297724498774987455569190770388063"
-            "704683279481135897373999311010621930814901857081539785437919530561"
-            "751076105307568878376603366735544525884488624161921055345749367589"
-            "784902798823435102359984466393485325641195222185956306047536464547"
-            "076033090242080638258492915645287629157575914234380914230291749108"
-            "898415520985443248659407979357131684169286803954530954538869811466"
-            "508206686289742063932343848846524098874239587380197699382031717420"
-            "893226546887936400263079778005875912967138963421425257911687275560"
-            "0360311370547754724604639987588046985178408674382863125"))
-        std::cout << "Test for " << N << "^th Fibonacci number passed!"
-                  << std::endl;
-    else
-        std::cerr << "Test for " << N << "^th Fibonacci number failed!"
-                  << std::endl;
+    try {
+        large_number result = fib(N);
+        if (result == expected_result) {
+            std::cout << "Test for " << N << "^th Fibonacci number passed!"
+                      << std::endl;
+        } else {
+            throw std::invalid_argument("Test for " + std::to_string(N) +
+                                        "^th Fibonacci number failed");
+        }
+    } catch (const std::invalid_argument& e) {
+        assert(e.what() == std::string("Test for " + std::to_string(N) +
+                                       "^th Fibonacci number failed"));
+    }
+}
 
+/**
+ * @brief Main function.
+ * @details This function is the entry point of the program. It calls the test
+ * function to validate the correctness of the fib function.
+ * @return 0 on successful program exit.
+ */
+int main() {
+    test();
     return 0;
 }