JIT compile option for binary minimization (ml-explore#1091)

* try cpp 20 for compile

* unary, binary, ternary in jit

* nits

* fix gather/scatter

* fix rebase

* reorg compile

* add ternary to compile

* jit copy

* jit compile flag

* fix build

* use linked function for ternary

* some nits

* docs + circle min size build

* docs + circle min size build

* fix extension

* fix no cpu build

* improve includes

.circleci/config.yml

@@ -114,7 +114,13 @@ jobs:
           name: Run CPP tests
           command: |
             DEVICE=gpu METAL_DEVICE_WRAPPER_TYPE=1 METAL_DEBUG_ERROR_MODE=0 ./build/tests/tests
-            DEVICE=cpu ./build/tests/tests
+      - run:
+          name: Build small binary
+          command: |
+            source env/bin/activate
+            cd build/
+            cmake .. -DCMAKE_BUILD_TYPE=MinSizeRel -DBUILD_SHARED_LIBS=ON -DMLX_BUILD_CPU=OFF -DMLX_BUILD_SAFETENSORS=OFF -DMLX_BUILD_GGUF=OFF -DMLX_METAL_JIT=ON
+            make -j
 
   build_release:
     parameters:

CMakeLists.txt

@@ -20,6 +20,7 @@ option(MLX_METAL_DEBUG "Enhance metal debug workflow" OFF)
 option(MLX_ENABLE_X64_MAC "Enable building for x64 macOS" OFF)
 option(MLX_BUILD_GGUF "Include support for GGUF format" ON)
 option(MLX_BUILD_SAFETENSORS "Include support for safetensors format" ON)
+option(MLX_METAL_JIT "Use JIT compilation for Metal kernels" OFF)
 option(BUILD_SHARED_LIBS "Build mlx as a shared library" OFF)
 
 if(NOT MLX_VERSION)
@@ -109,7 +110,7 @@ elseif (MLX_BUILD_METAL)
     $<INSTALL_INTERFACE:include/metal_cpp>
   )
   target_link_libraries(
-    mlx
+    mlx PUBLIC
     ${METAL_LIB}
     ${FOUNDATION_LIB}
     ${QUARTZ_LIB})
@@ -122,7 +123,7 @@ if (MLX_BUILD_CPU)
   if (MLX_BUILD_ARM AND ACCELERATE_LIBRARY)
     message(STATUS "Accelerate found ${ACCELERATE_LIBRARY}")
     set(MLX_BUILD_ACCELERATE ON)
-    target_link_libraries(mlx ${ACCELERATE_LIBRARY})
+    target_link_libraries(mlx PUBLIC ${ACCELERATE_LIBRARY})
     add_compile_definitions(ACCELERATE_NEW_LAPACK)
   else()
     message(STATUS "Accelerate or arm neon not found, using default backend.")
@@ -145,7 +146,7 @@ if (MLX_BUILD_CPU)
     message(STATUS "Lapack lib " ${LAPACK_LIBRARIES})
     message(STATUS "Lapack include " ${LAPACK_INCLUDE_DIRS})
     target_include_directories(mlx PRIVATE ${LAPACK_INCLUDE_DIRS})
-    target_link_libraries(mlx ${LAPACK_LIBRARIES})
+    target_link_libraries(mlx PUBLIC ${LAPACK_LIBRARIES})
     # List blas after lapack otherwise we may accidentally incldue an old version
     # of lapack.h from the include dirs of blas.
     find_package(BLAS REQUIRED)
@@ -160,7 +161,7 @@ if (MLX_BUILD_CPU)
     message(STATUS "Blas lib " ${BLAS_LIBRARIES})
     message(STATUS "Blas include " ${BLAS_INCLUDE_DIRS})
     target_include_directories(mlx PRIVATE ${BLAS_INCLUDE_DIRS})
-    target_link_libraries(mlx ${BLAS_LIBRARIES})
+    target_link_libraries(mlx PUBLIC ${BLAS_LIBRARIES})
   endif()
 else()
   set(MLX_BUILD_ACCELERATE OFF)
@@ -175,6 +176,14 @@ target_include_directories(
   $<INSTALL_INTERFACE:include>
 )
 
+FetchContent_Declare(fmt
+  GIT_REPOSITORY https://github.com/fmtlib/fmt.git
+  GIT_TAG 10.2.1 
+  EXCLUDE_FROM_ALL
+)
+FetchContent_MakeAvailable(fmt)
+target_link_libraries(mlx PRIVATE fmt::fmt-header-only)
+
 if (MLX_BUILD_PYTHON_BINDINGS)
   message(STATUS "Building Python bindings.")
   find_package(Python 3.8 COMPONENTS Interpreter Development.Module REQUIRED)

docs/src/install.rst

@@ -163,6 +163,8 @@ should point to the path to the built metal library.
      - ON
    * - MLX_BUILD_GGUF
      - ON
+   * - MLX_METAL_JIT
+     - OFF
 
 .. note::
 
@@ -196,9 +198,18 @@ GGUF, you can do:
   cmake ..
     -DCMAKE_BUILD_TYPE=MinSizeRel \
     -DBUILD_SHARED_LIBS=ON \
-    -DMLX_BUILD_CPU=ON \
+    -DMLX_BUILD_CPU=OFF \
     -DMLX_BUILD_SAFETENSORS=OFF \
     -DMLX_BUILD_GGUF=OFF
+    -DMLX_METAL_JIT=ON
+
+THE `MLX_METAL_JIT` flag minimizes the size of the MLX Metal library which
+contains pre-built GPU kernels. This substantially reduces the size of the
+Metal library by run-time compiling kernels the first time they are used in MLX
+on a given machine. Note run-time compilation incurs a cold-start cost which can
+be anwywhere from a few hundred millisecond to a few seconds depending on the
+application. Once a kernel is compiled, it will be cached by the system. The
+Metal kernel cache persists accross reboots.
 
 Troubleshooting
 ^^^^^^^^^^^^^^^

mlx/backend/common/binary.h

@@ -1,6 +1,8 @@
 // Copyright © 2023 Apple Inc.
 
 #pragma once
+#include <cassert>
+
 #include "mlx/allocator.h"
 #include "mlx/array.h"
 #include "mlx/backend/common/utils.h"

mlx/backend/common/cholesky.cpp

@@ -98,12 +98,4 @@ void Cholesky::eval(const std::vector<array>& inputs, array& output) {
   cholesky_impl(inputs[0], output, upper_);
 }
 
-std::pair<std::vector<array>, std::vector<int>> Cholesky::vmap(
-    const std::vector<array>& inputs,
-    const std::vector<int>& axes) {
-  auto ax = axes[0] >= 0 ? 0 : -1;
-  auto a = axes[0] > 0 ? moveaxis(inputs[0], axes[0], 0, stream()) : inputs[0];
-  return {{linalg::cholesky(a, upper_, stream())}, {ax}};
-}
-
 } // namespace mlx::core

mlx/backend/metal/CMakeLists.txt

@@ -1,33 +1,80 @@
-add_custom_command(
-    OUTPUT  compiled_preamble.cpp
+function(make_jit_source SRC_NAME)
+  # This function takes a metal header file,
+  # runs the C preprocessesor on it, and makes
+  # the processed contents available as a string in a C++ function
+  # mlx::core::metal::${SRC_NAME}()
+  #
+  # To use the function, declare it in jit/includes.h and
+  # include jit/includes.h.
+  #
+  # Additional arguments to this function are treated as dependencies
+  # in the Cmake build system.
+  add_custom_command(
+    OUTPUT  jit/${SRC_NAME}.cpp
     COMMAND /bin/bash
               ${CMAKE_CURRENT_SOURCE_DIR}/make_compiled_preamble.sh
-              ${CMAKE_CURRENT_BINARY_DIR}/compiled_preamble.cpp
+              ${CMAKE_CURRENT_BINARY_DIR}/jit
               ${CMAKE_C_COMPILER}
               ${PROJECT_SOURCE_DIR}
+              ${SRC_NAME}
               "-D${MLX_METAL_VERSION}"
     DEPENDS make_compiled_preamble.sh
-            kernels/compiled_preamble.h
-            kernels/unary.h
-            kernels/binary.h
-            kernels/bf16.h
-            kernels/erf.h
-            kernels/expm1f.h
-            kernels/utils.h
-            kernels/bf16_math.h
-)
+            kernels/${SRC_NAME}.h
+            ${ARGN}
+  )
+  add_custom_target(${SRC_NAME} DEPENDS jit/${SRC_NAME}.cpp)
+  add_dependencies(mlx ${SRC_NAME})
+  target_sources(
+    mlx
+    PRIVATE
+    ${CMAKE_CURRENT_BINARY_DIR}/jit/${SRC_NAME}.cpp
+  )
+endfunction(make_jit_source)
 
-add_custom_target(
-  compiled_preamble
-  DEPENDS compiled_preamble.cpp
+make_jit_source(
+  utils
+  kernels/bf16.h
+  kernels/complex.h
+)
+make_jit_source(
+  unary_ops
+  kernels/erf.h
+  kernels/expm1f.h
 )
+make_jit_source(binary_ops)
+make_jit_source(ternary_ops)
+make_jit_source(
+  reduction
+  kernels/atomic.h
+  kernels/reduction/ops.h
+)
+make_jit_source(scatter)
+make_jit_source(gather)
 
-add_dependencies(mlx compiled_preamble)
+if (MLX_METAL_JIT) 
+  target_sources(
+    mlx
+    PRIVATE
+    ${CMAKE_CURRENT_SOURCE_DIR}/jit_kernels.cpp
+  )
+  make_jit_source(copy)
+  make_jit_source(unary)
+  make_jit_source(binary)
+  make_jit_source(binary_two)
+  make_jit_source(ternary)
+else()
+  target_sources(
+    mlx
+    PRIVATE
+    ${CMAKE_CURRENT_SOURCE_DIR}/nojit_kernels.cpp
+  )
+endif()
 
 target_sources(
   mlx
   PRIVATE
   ${CMAKE_CURRENT_SOURCE_DIR}/allocator.cpp
+  ${CMAKE_CURRENT_SOURCE_DIR}/binary.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/compiled.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/conv.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/copy.cpp
@@ -46,7 +93,8 @@ target_sources(
   ${CMAKE_CURRENT_SOURCE_DIR}/softmax.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/sort.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/reduce.cpp
-  ${CMAKE_CURRENT_BINARY_DIR}/compiled_preamble.cpp
+  ${CMAKE_CURRENT_SOURCE_DIR}/ternary.cpp
+  ${CMAKE_CURRENT_SOURCE_DIR}/unary.cpp
 )
 
 if (NOT MLX_METAL_PATH)