add Int8Float class

6 files changed, 119 insertions, 0 deletions

diff --git a/eval/CMakeLists.txt b/eval/CMakeLists.txt
index 05ac4cb78ab..7d3d94d7ed6 100644
--- a/eval/CMakeLists.txt
+++ b/eval/CMakeLists.txt
@@ -21,6 +21,7 @@ vespa_define_module(
     src/tests/eval/gbdt
     src/tests/eval/gen_spec
     src/tests/eval/inline_operation
+    src/tests/eval/int8float
     src/tests/eval/interpreted_function
     src/tests/eval/multiply_add
     src/tests/eval/nested_loop
diff --git a/eval/src/tests/eval/int8float/CMakeLists.txt b/eval/src/tests/eval/int8float/CMakeLists.txt
new file mode 100644
index 00000000000..fb258f46fc2
--- /dev/null
+++ b/eval/src/tests/eval/int8float/CMakeLists.txt
@@ -0,0 +1,9 @@
+# Copyright Verizon Media. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+vespa_add_executable(eval_int8float_test_app TEST
+    SOURCES
+    int8float_test.cpp
+    DEPENDS
+    vespaeval
+    GTest::GTest
+)
+vespa_add_test(NAME eval_int8float_test_app COMMAND eval_int8float_test_app)
diff --git a/eval/src/tests/eval/int8float/int8float_test.cpp b/eval/src/tests/eval/int8float/int8float_test.cpp
new file mode 100644
index 00000000000..9debf712150
--- /dev/null
+++ b/eval/src/tests/eval/int8float/int8float_test.cpp
@@ -0,0 +1,59 @@
+// Copyright Verizon Media. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#include <vespa/eval/eval/int8float.h>
+#include <vespa/vespalib/objects/nbostream.h>
+#include <vespa/vespalib/gtest/gtest.h>
+#include <cmath>
+
+using namespace vespalib;
+using namespace vespalib::eval;
+
+static std::vector<float> simple_values = {
+    0.0, 1.0, -1.0, -17.0, 42.0, 127.0, -128.0
+};
+
+TEST(Int8FloatTest, normal_usage) {
+    EXPECT_EQ(sizeof(float), 4);
+    EXPECT_EQ(sizeof(Int8Float), 1);
+    Int8Float answer = 42;
+    double fortytwo = answer;
+    EXPECT_EQ(fortytwo, 42);
+    for (float value : simple_values) {
+        Int8Float b = value;
+        float recover = b;
+        EXPECT_EQ(value, recover);
+    }
+    // undefined behavior here:
+    Int8Float b1 = 128.0;
+    EXPECT_NE(float(b1), 128.0);
+    Int8Float b2 = -129.0;
+    EXPECT_NE(float(b2), -129.0);
+}
+
+TEST(Int8FloatTest, with_nbostream) {
+    nbostream buf;
+    for (Int8Float value : simple_values) {
+        buf << value;
+    }
+    for (float value : simple_values) {
+        Int8Float stored;
+        buf >> stored;
+        EXPECT_EQ(float(stored), value);
+    }
+}
+
+TEST(Int8FloatTest, traits_check) {
+        EXPECT_TRUE(std::is_trivially_constructible<Int8Float>::value);
+        EXPECT_TRUE(std::is_trivially_move_constructible<Int8Float>::value);
+        EXPECT_TRUE(std::is_trivially_default_constructible<Int8Float>::value);
+        EXPECT_TRUE((std::is_trivially_assignable<Int8Float,Int8Float>::value));
+        EXPECT_TRUE(std::is_trivially_move_assignable<Int8Float>::value);
+        EXPECT_TRUE(std::is_trivially_copy_assignable<Int8Float>::value);
+        EXPECT_TRUE(std::is_trivially_copyable<Int8Float>::value);
+        EXPECT_TRUE(std::is_trivially_destructible<Int8Float>::value);
+        EXPECT_TRUE(std::is_trivial<Int8Float>::value);
+        EXPECT_TRUE(std::is_swappable<Int8Float>::value);
+        EXPECT_TRUE(std::has_unique_object_representations<Int8Float>::value);
+}
+
+GTEST_MAIN_RUN_ALL_TESTS()
diff --git a/eval/src/vespa/eval/eval/CMakeLists.txt b/eval/src/vespa/eval/eval/CMakeLists.txt
index 2c0922e617c..639ac3b5864 100644
--- a/eval/src/vespa/eval/eval/CMakeLists.txt
+++ b/eval/src/vespa/eval/eval/CMakeLists.txt
@@ -15,6 +15,7 @@ vespa_add_library(eval_eval OBJECT
     fast_value.cpp
     function.cpp
     gbdt.cpp
+    int8float.cpp
     interpreted_function.cpp
     key_gen.cpp
     lazy_params.cpp
diff --git a/eval/src/vespa/eval/eval/int8float.cpp b/eval/src/vespa/eval/eval/int8float.cpp
new file mode 100644
index 00000000000..38af441fd08
--- /dev/null
+++ b/eval/src/vespa/eval/eval/int8float.cpp
@@ -0,0 +1,3 @@
+// Copyright Verizon Media. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#include "int8float.h"
diff --git a/eval/src/vespa/eval/eval/int8float.h b/eval/src/vespa/eval/eval/int8float.h
new file mode 100644
index 00000000000..7279d519bed
--- /dev/null
+++ b/eval/src/vespa/eval/eval/int8float.h
@@ -0,0 +1,46 @@
+// Copyright Verizon Media. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#pragma once
+
+#include <cstdint>
+#include <vespa/vespalib/objects/nbostream.h>
+
+namespace vespalib::eval {
+
+/**
+ * Class holding an 8-bit integer which decays into float.
+ **/
+class Int8Float {
+private:
+    int8_t _bits;
+public:
+    constexpr Int8Float(float value) noexcept : _bits(value) {}
+    Int8Float() noexcept = default;
+    ~Int8Float() noexcept = default;
+    constexpr Int8Float(const Int8Float &other) noexcept = default;
+    constexpr Int8Float(Int8Float &&other) noexcept = default;
+    constexpr Int8Float& operator=(const Int8Float &other) noexcept = default;
+    constexpr Int8Float& operator=(Int8Float &&other) noexcept = default;
+    constexpr Int8Float& operator=(float value) noexcept {
+        _bits = value;
+        return *this;
+    }
+
+    constexpr operator float () const noexcept { return _bits; }
+
+    constexpr float to_float() const noexcept { return _bits; }
+    constexpr void assign(float value) noexcept { _bits = value; }
+
+    constexpr int8_t get_bits() const { return _bits; }
+    constexpr void assign_bits(int8_t value) noexcept { _bits = value; }
+};
+
+inline nbostream & operator << (nbostream &stream, Int8Float v)   { return stream << v.get_bits(); }
+inline nbostream & operator >> (nbostream &stream, Int8Float & v) {
+    int8_t byte;
+    stream >> byte;
+    v.assign_bits(byte);
+    return stream;
+}
+
+}