rediscovered Diophantine equation problem in float conversion to bina…

…ry rational
stillwater-sc · Nov 14, 2024 · 9f96c99 · 9f96c99
1 parent da74726
commit 9f96c99
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Showing 2 changed files with 23 additions and 9 deletions.
diff --git a/include/universal/number/rational/rational_impl.hpp b/include/universal/number/rational/rational_impl.hpp
@@ -337,16 +337,27 @@ class rational {
 		uint64_t e{ 0 }, f{ 0 };
 		bool s{ false };
 		extractFields(rhs, s, e, f, bits);
-
+		int exponent = static_cast<int>(e - ieee754_parameter<Real>::bias);
 		if (e == 0) { // subnormal
 		}
 		else { // normal
 			uint64_t a = f | ieee754_parameter<Real>::hmask;
 			uint64_t b = ieee754_parameter<Real>::hmask;
-			int exponent = static_cast<int>(e - ieee754_parameter<Real>::bias);
-//			std::cout << "exponent = " << exponent << '\n';
-//			std::cout << "a        = " << to_binary(a) << '\n';
-//			std::cout << "b        = " << to_binary(b) << '\n';
+
+			//std::cout << "exponent = " << exponent << '\n';
+			//std::cout << "a        = " << to_binary(a) << '\n';
+			//std::cout << "b        = " << to_binary(b) << '\n';
+
+			// remove any redundancy in the representation
+			uint64_t rr{ 0 }, aa{ a }, bb{ b };
+			while (aa % bb > 0ull) {
+				rr = aa % bb;
+				aa = bb;
+				bb = rr;
+			}
+			a /= bb;
+			b /= bb;
+
 			if (exponent == 0 && a == b) {
 				n = 1;
 				d = 1;

diff --git a/static/rational/conversion/assignment.cpp b/static/rational/conversion/assignment.cpp
@@ -105,27 +105,30 @@ try {
 
 	std::string test_suite  = "rational float assignment validation";
 	std::string test_tag    = "assignment";
-	bool reportTestCases    = true;
+	bool reportTestCases    = false;
 	int nrOfFailedTestCases = 0;
 
 	ReportTestSuiteHeader(test_suite, reportTestCases);
 
 #if MANUAL_TESTING
 
-	rb64 a,b;
+	rb16 a,b;
 	a.set(0x02, 0x0A);
 	std::cout << to_binary(a) << '\n';
 	double da = double(a);
 	b = da;
 	std::cout << to_binary(da) << " : " << da << '\n';
-	std::cout << a << '\n';
-	std::cout << b << '\n';
+	std::cout << to_binary(a) << " : " << a << '\n';
+	std::cout << to_binary(b) << " : " << b << '\n';
 
 	Ranges(1.0f);
 
 	// manual exhaustive test
 	//
 	nrOfFailedTestCases += ReportTestResult(ValidateAssignment<rb8>(reportTestCases), type_tag(rb8()), test_tag);
+	nrOfFailedTestCases += ReportTestResult(ValidateAssignment<rb16>(reportTestCases), type_tag(rb16()), test_tag);
+//	nrOfFailedTestCases += ReportTestResult(ValidateAssignment<rb32>(reportTestCases), type_tag(rb32()), test_tag);
+	nrOfFailedTestCases += ReportTestResult(ValidateAssignment<rb64>(reportTestCases), type_tag(rb64()), test_tag);
 
 	ReportTestSuiteResults(test_suite, nrOfFailedTestCases);
 	return EXIT_SUCCESS;