diff --git a/.github/workflows/benchmark.yml b/.github/workflows/benchmark.yml
index 39683de1..319f794c 100644
--- a/.github/workflows/benchmark.yml
+++ b/.github/workflows/benchmark.yml
@@ -44,7 +44,7 @@ jobs:
 
       - name: Build
         working-directory: ${{env.BENCH_ROOT}}/build-bench
-        run: cmake --build . --parallel 1
+        run: cmake --build . --parallel 4
 
       - name: Benchmark
         working-directory: ${{env.BENCH_ROOT}}/build-bench
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index b279802b..353a3954 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -44,7 +44,7 @@ jobs:
 
       - name: Build
         working-directory: ${{env.TEST_ROOT}}/build-test
-        run: cmake --build . --parallel 1
+        run: cmake --build . --parallel 4
 
       - name: Test
         working-directory: ${{env.TEST_ROOT}}/build-test
diff --git a/MobileGL/MG_Impl/GLImpl/Program/GL_Program.cpp b/MobileGL/MG_Impl/GLImpl/Program/GL_Program.cpp
index d65a1db5..aaf53306 100644
--- a/MobileGL/MG_Impl/GLImpl/Program/GL_Program.cpp
+++ b/MobileGL/MG_Impl/GLImpl/Program/GL_Program.cpp
@@ -140,7 +140,23 @@ namespace MobileGL {
         }
 
         void GetAttachedShaders_State(GLuint program, GLsizei maxCount, GLsizei* count, GLuint* shaders) {
-            THROW_UNIMPL_EXCEPTION;
+            if (maxCount < 0) {
+                MG_State::pGLContext->RecordError(
+                        ErrorCode::InvalidValue,
+                        MakeShared<GenericErrorInfo>("MG_Impl/GLImpl", __func__,
+                                                     "`maxCount` is less than 0."));
+                return;
+            }
+            auto programObject = TryToGetProgramObject(program);
+            if (!programObject)
+                return;
+            const auto& s = programObject->GetAttachedShaders();
+            GLsizei c = std::min((GLsizei)s.size(), maxCount);
+            if (count)
+                *count = c;
+            for (GLsizei i = 0; i < c; ++i) {
+                shaders[i] = s[i]->GetId();
+            }
         }
 
         GLint GetAttribLocation_State(GLuint program, const GLchar* name) {
@@ -164,7 +180,23 @@ namespace MobileGL {
         }
 
         void GetShaderSource_State(GLuint shader, GLsizei bufSize, GLsizei* length, GLchar* source) {
-            THROW_UNIMPL_EXCEPTION;
+            if (bufSize < 0) {
+                MG_State::pGLContext->RecordError(
+                        ErrorCode::InvalidValue,
+                        MakeShared<GenericErrorInfo>("MG_Impl/GLImpl", __func__,
+                                                     "`bufSize` is less than 0."));
+            }
+
+            auto shaderObject = TryToGetShaderObject(shader);
+            if (!shaderObject)
+                return;
+
+            auto& src = shaderObject->GetShaderSource();
+            auto sz = std::min(bufSize - 1, (GLsizei)src.length());
+            if (length)
+                *length = sz;
+            memcpy(source, src.c_str(), sz);
+            source[sz] = '\0';
         }
 
         GLint GetUniformLocation_State(GLuint program, const GLchar* name) {
@@ -203,11 +235,36 @@ namespace MobileGL {
         }
 
         void ShaderSource_State(GLuint shader, GLsizei count, const GLchar* const* string, const GLint* length) {
-            THROW_UNIMPL_EXCEPTION;
+            if (count < 0) {
+                MG_State::pGLContext->RecordError(
+                    ErrorCode::InvalidValue,
+                    MakeShared<GenericErrorInfo>("MG_Impl/GLImpl", __func__,
+                                             "`count` is less than 0."));
+            }
+
+            auto shaderObject = TryToGetShaderObject(shader);
+            if (!shaderObject)
+                return;
+
+            std::string src;
+            for (GLsizei i = 0; i < count; i++) {
+                src +=
+                    (length[i] <= 0) ? string[i] : std::string(string[i], length[i]);
+            }
+            shaderObject->SetShaderSource(Move(src));
         }
 
         void UseProgram_State(GLuint program) {
-            THROW_UNIMPL_EXCEPTION;
+            if (program == 0) {
+                MG_State::pGLContext->UseProgram(0);
+                return;
+            }
+
+            auto programObject = TryToGetProgramObject(program);
+            if (!programObject)
+                return;
+            MG_State::pGLContext->UseProgram(program);
+
         }
 
         void Uniform1f_State(GLint location, GLfloat v0) {
diff --git a/MobileGL/MG_State/GLState/Core.cpp b/MobileGL/MG_State/GLState/Core.cpp
index 92c190ea..3f28f6f4 100644
--- a/MobileGL/MG_State/GLState/Core.cpp
+++ b/MobileGL/MG_State/GLState/Core.cpp
@@ -187,6 +187,10 @@ namespace MobileGL {
             SharedPtr<ShaderObject> GLContext::GetShaderObject(const Uint index) {
                 return m_programState.GetShaderObject(index);
             }
+
+            void GLContext::UseProgram(Uint program) {
+                return m_programState.UseProgram(program);
+            }
         } // namespace GLState
 
         GLState::GLContext* pGLContext;
diff --git a/MobileGL/MG_State/GLState/Core.h b/MobileGL/MG_State/GLState/Core.h
index b3bb10c6..e57d0785 100644
--- a/MobileGL/MG_State/GLState/Core.h
+++ b/MobileGL/MG_State/GLState/Core.h
@@ -63,6 +63,7 @@ namespace MobileGL {
                 Bool ValidateShaderName(Uint index) const;
                 SharedPtr<ProgramObject> GetProgramObject(Uint index);
                 SharedPtr<ShaderObject> GetShaderObject(Uint index);
+                void UseProgram(Uint program);
             private:
                 // Error
                 ErrorState m_errorState;
diff --git a/MobileGL/MG_State/GLState/ProgramState/ProgramObject.cpp b/MobileGL/MG_State/GLState/ProgramState/ProgramObject.cpp
index a82c57a9..db9bc49a 100644
--- a/MobileGL/MG_State/GLState/ProgramState/ProgramObject.cpp
+++ b/MobileGL/MG_State/GLState/ProgramState/ProgramObject.cpp
@@ -59,6 +59,10 @@ namespace MobileGL {
             void ProgramObject::MarkAsDeleted() {
                 m_deleteStatus = true;
             }
+
+            Vector<SharedPtr<ShaderObject>>& ProgramObject::GetAttachedShaders() {
+                return m_shaders;
+            }
         } // namespace GLState
     } // namespace MG_State
 } // namespace MobileGL
\ No newline at end of file
diff --git a/MobileGL/MG_State/GLState/ProgramState/ProgramObject.h b/MobileGL/MG_State/GLState/ProgramState/ProgramObject.h
index 1946707d..a4e5b1b5 100644
--- a/MobileGL/MG_State/GLState/ProgramState/ProgramObject.h
+++ b/MobileGL/MG_State/GLState/ProgramState/ProgramObject.h
@@ -7,12 +7,15 @@ namespace MobileGL {
         namespace GLState {
             class ProgramObject {
             public:
+                ProgramObject(const Uint id): m_id(id) {}
                 bool ShaderIsAttached(SharedPtr<ShaderObject> shader);
                 bool AttachShader(SharedPtr<ShaderObject> shader);
                 SizeT DetachShader(SharedPtr<ShaderObject> shader);
                 void Link();
                 void MarkAsDeleted();
+                Vector<SharedPtr<ShaderObject>>& GetAttachedShaders();
             private:
+                const Uint m_id = 0;
                 Vector<SharedPtr<ShaderObject>> m_shaders;
                 // basically this contains SPIR-V in binary format
                 Vector<Vector<Uint>> m_programBinary;
diff --git a/MobileGL/MG_State/GLState/ProgramState/ProgramState.cpp b/MobileGL/MG_State/GLState/ProgramState/ProgramState.cpp
index b90c276d..fb7f22eb 100644
--- a/MobileGL/MG_State/GLState/ProgramState/ProgramState.cpp
+++ b/MobileGL/MG_State/GLState/ProgramState/ProgramState.cpp
@@ -33,11 +33,19 @@ namespace MobileGL {
                 return CheckIndexAvail(program, m_programObjects) && m_programObjects[program] != nullptr;
             }
 
+            void ProgramState::UseProgram(Uint program) {
+                if (program == 0)
+                    m_currentProgram.reset();
+
+                if (!CheckIndexAvail(program, m_programObjects)) return;
+                m_currentProgram = m_programObjects[program];
+            }
+
             Uint ProgramState::CreateShader(ShaderStage stage) {
                 Uint shaderId = 0;
                 m_shaderIndexGenerator.Generate(1, &shaderId);
                 EnsureIndexAvail(shaderId, m_shaderObjects);
-                auto shaderObject = MakeShared<ShaderObject>(stage);
+                auto shaderObject = MakeShared<ShaderObject>(stage, shaderId);
                 if (shaderObject == nullptr)
                     return 0;
                 m_shaderObjects[shaderId] = shaderObject;
diff --git a/MobileGL/MG_State/GLState/ProgramState/ProgramState.h b/MobileGL/MG_State/GLState/ProgramState/ProgramState.h
index 85a653a0..ff981cb1 100644
--- a/MobileGL/MG_State/GLState/ProgramState/ProgramState.h
+++ b/MobileGL/MG_State/GLState/ProgramState/ProgramState.h
@@ -15,6 +15,8 @@ namespace MobileGL {
                 void MarkProgramObjectForDeletion(Uint program);
                 Bool ValidateProgramObject(Uint program) const;
 
+                void UseProgram(Uint program);
+
                 Uint CreateShader(ShaderStage stage);
                 SharedPtr<ShaderObject> GetShaderObject(Uint shader);
                 void MarkShaderObjectForDeletion(Uint shader);
@@ -38,6 +40,8 @@ namespace MobileGL {
 
                 IndexGenerator<Uint> m_shaderIndexGenerator;
                 Vector<SharedPtr<ShaderObject>> m_shaderObjects;
+
+                SharedPtr<ProgramObject> m_currentProgram;
             };
         } // namespace GLState
     } // namespace MG_State
diff --git a/MobileGL/MG_State/GLState/ProgramState/ShaderObject.cpp b/MobileGL/MG_State/GLState/ProgramState/ShaderObject.cpp
index fbbd93de..3345f025 100644
--- a/MobileGL/MG_State/GLState/ProgramState/ShaderObject.cpp
+++ b/MobileGL/MG_State/GLState/ProgramState/ShaderObject.cpp
@@ -8,6 +8,10 @@ namespace MobileGL {
                 m_source = source;
             }
 
+            void ShaderObject::SetShaderSource(std::string &&source) {
+                m_source = Move(source);
+            }
+
             void ShaderObject::Compile() {
                 using namespace MG_Util::ShaderTranspiler;
                 ShaderAttrib attrib{
diff --git a/MobileGL/MG_State/GLState/ProgramState/ShaderObject.h b/MobileGL/MG_State/GLState/ProgramState/ShaderObject.h
index c743a629..271c7939 100644
--- a/MobileGL/MG_State/GLState/ProgramState/ShaderObject.h
+++ b/MobileGL/MG_State/GLState/ProgramState/ShaderObject.h
@@ -56,15 +56,18 @@ namespace MobileGL {
 
             class ShaderObject {
             public:
-                ShaderObject(const ShaderStage stage) : m_stage(stage) {}
+                ShaderObject(const ShaderStage stage, const Uint id) : m_stage(stage), m_id(id) {}
                 void SetShaderSource(const std::string& source);
+                void SetShaderSource(std::string&& source);
                 void Compile();
                 void MarkAsDeleted();
 
+                Uint GetId() const { return m_id; }
                 ShaderStage GetShaderStage() const { return m_stage; }
                 const std::string& GetShaderSource() const { return m_source; }
                 SharedPtr<glslang::TShader> GetCompiledShader() const { return m_shader; }
             private:
+                const Uint m_id = 0;
                 const ShaderStage m_stage;
                 std::string m_source;
                 SharedPtr<glslang::TShader> m_shader;