Taichi

Highlights:
- **Command line interface**
- Add 'ti repl' command for Taichi REPL shell (1765) (by **彭于斌**)
- **GUI**
- Support gui.arrow_field() and gui.point_field() for small resolution vector / scalar field visualization (1763) (by **彭于斌**)
- **Intermediate representation**
- Support SAR operator: x >> y (1772) (by **Hanke Liu**)
- Support SHL operator: x << y (1762) (by **Xuanda Yang**)
- **Refactor**
- ti.classfunc and ti.classkernel are obsolete. Directly use ti.func and ti.kernel instead (1770) (by **彭于斌**)
- 'ti.var' is deprecated, use 'ti.field' instead (1767) (by **彭于斌**)

Full changelog:
- [CLI] [doc] Add 'ti repl' command for Taichi REPL shell (1765) (by **彭于斌**)
- [IR] [lang] Support SAR operator: x >> y (1772) (by **Hanke Liu**)
- [async] [benchmark] Enable optimization for global variables after fusion (1776) (by **xumingkuan**)
- [benchmark] [async] Improve AsyncEngine benchmarks (1774) (by **Yuanming Hu**)
- [GUI] Support gui.arrow_field() and gui.point_field() for small resolution vector / scalar field visualization (1763) (by **彭于斌**)
- [Refactor] ti.classfunc and ti.classkernel are obsolete. Directly use ti.func and ti.kernel instead (1770) (by **彭于斌**)
- [IR] [lang] Support SHL operator: x << y (1762) (by **Xuanda Yang**)
- [Refactor] 'ti.var' is deprecated, use 'ti.field' instead (1767) (by **彭于斌**)
- [benchmark] [async] Improve AsyncEngine benchmarks (1758) (by **Yuanming Hu**)
- [misc] Fix a typo in README.md (1760) (by **fq**)
- [benchmark] [async] Add ti.benchmark_plot and add fuse_dense.py to benchmarks (1754) (by **xumingkuan**)

Highlights:
- **Error messages**
- Attach a traceback to ti.field when 'Some variable(s) are not placed' (1734) (by **彭于斌**)
- **Examples**
- Upgrade mass_spring_3d.py to Taichi THREE v0.0.3 API (1732) (by **彭于斌**)
- **GUI**
- Add handy ti.imscale(img, w, h) for scaling image (1735) (by **彭于斌**)
- **IR optimization passes**
- Identical store/load elimination by control-flow graph (1741) (by **xumingkuan**)

Full changelog:
- [GUI] Add handy ti.imscale(img, w, h) for scaling image (1735) (by **彭于斌**)
- [benchmark] [async] Add more statistics for async benchmark (1747) (by **xumingkuan**)
- [misc] Fix OffloadedStmt cloning (1745) (by **Yuanming Hu**)
- [refactor] Use condition variable instead of sleep in ParallelExecutor (1743) (by **Ye Kuang**)
- [cc] [refactor] C backend use result_buffer for return value too (1736) (by **彭于斌**)
- [Error] Attach a traceback to ti.field when 'Some variable(s) are not placed' (1734) (by **彭于斌**)
- [benchmark] Dump the benchmark data into one yaml file (1744) (by **xumingkuan**)
- [benchmark] Upgrade "benchmarks" to new syntax (1729) (by **Xudong Feng**)
- [misc] Upgrade "misc" to the new syntax (1730) (by **Xudong Feng**)
- [misc] Create misc/examples.md for more examples (1726) (by **Yuanming Hu**)
- [opt] Add irpass::analysis::same_value (1742) (by **xumingkuan**)
- [Opt] Identical store/load elimination by control-flow graph (1741) (by **xumingkuan**)
- [example] Upgrade pbf2d.py to new syntax (1710) (by **彭于斌**)
- [Example] Upgrade mass_spring_3d.py to Taichi THREE v0.0.3 API (1732) (by **彭于斌**)

Highlights:
- **Documentation**
- Add API reference for external array interactions (1677) (by **彭于斌**)
- **Language and syntax**
- Support printing scalar fields in Python-scope (1701) (by **彭于斌**)

Full changelog:
- [cuda] Refactor CUDA kernel launching (1738) (by **Yuanming Hu**)
- [blender] [example] Fix examples/waterwave.py memory leakage in Blender (1733) (by **彭于斌**)
- [refactor] Add Kernel::LaunchContextBuilder skeleton code (1723) (by **Ye Kuang**)
- [opengl] [refactor] Use result_buffer for return value since k-ye insist to (1724) (by **彭于斌**)
- [Lang] Support printing scalar fields in Python-scope (1701) (by **彭于斌**)
- [misc] Reformat all the files and rename "type_check" & "lower_ast" (1728) (by **Taichi Gardener**)
- [misc] Rename "fully_deprecated" to "obsolete" (1725) (by **Yuanming Hu**)
- [misc] [refactor] Replace the word tensor by field in comments and error messages (1721) (by **彭于斌**)
- [opengl] Cache GL_MAX_COMPUTE_WORK_GROUP_INVOCATIONS value to prevent glGetInteger per-launch (1718) (by **彭于斌**)
- [example] [refactor] Replace global field ti.Vector -> ti.Vector.field in examples (1716) (by **Xudong Feng**)
- [pypi] Upgrade sourceinspect to 0.0.3 for hot fixes (1717) (by **彭于斌**)
- [example] Make jacobi iteration 2x faster in stable_fluid.py (1713) (by **彭于斌**)
- [example] [refactor] Replace all ti.var->ti.field in our examples (1712) (by **Xudong Feng**)
- [metal] Pass back return values via result_buffer (1709) (by **Ye Kuang**)
- [refactor] Fix missed ti.var -> ti.field refactors in codebase (1705) (by **彭于斌**)
- [Doc] Add API reference for external array interactions (1677) (by **彭于斌**)
- [cli] [workflow] Support "\r\n" -> "\n" convert in "ti format" command (1706) (by **彭于斌**)

Highlights:
- **C source backend**
- Release the C backend (1707) (by **彭于斌**)
- **Documentation**
- Typo and grammatical fixes in vector documentation (1695) (by **Aryan Soman**)
- **Sparse computation**
- Support memory profiling for LLVM backends (1655) (by **Yuanming Hu**)

Full changelog:
- [mac] Add NSAutoreleasePool to manage obj-c objects' lifetime (1704) (by **Ye Kuang**)
- [CC] Release the C backend (1707) (by **彭于斌**)
- [test] [refactor] Replace ti.Vector or ti.Vector.var -> ti.Vector.field (1698) (by **Xudong Feng**)
- [example] [misc] Add 'ti.taichi_logo' function & misc typo fix (1640) (by **彭于斌**)
- [metal] Log errors if the compute kernel compilation failed (1697) (by **Ye Kuang**)
- [test] Fix Torch IO test (1700) (by **Yuanming Hu**)
- [misc] Update README.md gallery for the newly added examples during GAMES 201 (1652) (by **彭于斌**)
- [test] [refactor] Replace global field ti.Matrix or ti.Matrix.var -> ti.Matrix.field in python tests (1694) (by **Xudong Feng**)
- [Doc] Typo and grammatical fixes in vector documentation (1695) (by **Aryan Soman**)
- [example] [refactor] Upgrade to ti.field syntax for many examples (1669) (by **彭于斌**)
- [test] Replace ti.var by ti.field in tests starting with r-z (1684) (by **Xudong Feng**)
- [async] [cuda] AsyncEngine now supports CUDA (1687) (by **Yuanming Hu**)
- [Sparse] [llvm] Support memory profiling for LLVM backends (1655) (by **Yuanming Hu**)

Highlights:
- **Documentation**
- Improve Taichi kernels and functions definition (1576) (by **彭于斌**)
- **Examples**
- Add mpm3d.py for dimension-independent MPM method (1639) (by **彭于斌**)
- **IPython and other shells**
- Use 'sourceinspect' to support Blender scripting module and IDLE shell (1664) (by **彭于斌**)

Full changelog:
- [Example] Add mpm3d.py for dimension-independent MPM method (1639) (by **彭于斌**)
- [misc] Prevent 'supported_archs()' invocation in 'adaptive_arch_select()' for better compatibility (1666) (by **彭于斌**)
- [test] Replace ti.var by ti.field in tests starting with h-q (1683) (by **Xudong Feng**)
- [test] Replace ti.var by ti.field in tests starting with a-g (1681) (by **Xudong Feng**)
- Turn on the CC backend in the Dockerfile (1680) (by **samuela**)
- [llvm] Obsolete LLVM 8 support (1685) (by **Yuanming Hu**)
- [Doc] [refactor] Improve Taichi kernels and functions definition (1576) (by **彭于斌**)
- [cli] Add 'ti diagnose' command for providing system informations (1671) (by **彭于斌**)
- [cc] Add ti.cfg.cc_compile_cmd and ti.cfg.cc_link_cmd (1645) (by **彭于斌**)
- [IPython] Use 'sourceinspect' to support Blender scripting module and IDLE shell (1664) (by **彭于斌**)
- [misc] Add links to the mirror repo in Gitee (1665) (by **彭于斌**)
- [misc] Update doc version (1672) (by **Yuanming Hu**)
- [misc] [refactor] Add fully_deprecated mark for future use (1656) (by **彭于斌**)
- [doc] Fix uncovered while deprecated term 'tensor' occurance (1653) (by **彭于斌**)

Highlights:
- **Bug fixes**
- Fix random side-effect causing SSA violation in ti.Vector (1631) (by **彭于斌**)
- **Documentation**
- Replace fields of xxx by xxx field (1599) (by **Xudong Feng**)
- Replace "tensor" by "field" in documentation (1633) (by **Xudong Feng**)
- Improve type.rst readability (1618) (by **彭于斌**)
- **Examples**
- Add cg_possion.py, a Poisson solver based on conjugate gradients (1595) (by **彭于斌**)
- Enhance stable_fluid.py with BFECC, RK2, RK3 and Taichi's new syntax (1617) (by **彭于斌**)
- **GUI**
- Support gui.fps_limit and reduce idle power consumption (1611) (by **彭于斌**)
- Support images with 2 channels (RG) in GUI.set_image (1624) (by **彭于斌**)
- Support gui.arrow() and gui.arrows() (1625) (by **彭于斌**)
- **Language and syntax**
- Support float and int as aliases for default-precision data types (1585) (by **彭于斌**)
- **Miscellaneous**
- Catch RuntimeError when detecting backends for better compatibility (1647) (by **彭于斌**)
- **IR optimization passes**
- Improve aliasing analysis for SNodes with trailing bits (1657) (by **xumingkuan**)
- Improve the binary ops simplify pass (1646) (by **xumingkuan**)
- **Refactor**
- "x.snode()" is deprecated, use "x.snode" instead (1654) (by **彭于斌**)

Full changelog:
- [bug] [sparse] Fix struct-fors on pointer SNodes (1662) (by **Yuanming Hu**)
- [misc] [linux] Further improve misc/linker.map to prevent Blender segementation fault (1661) (by **彭于斌**)
- [doc] Re-update documentation on autodiff (1623) (by **彭于斌**)
- [Opt] Improve aliasing analysis for SNodes with trailing bits (1657) (by **xumingkuan**)
- `bgcolor` -> `background_color` in GUI docs (1660) (by **samuela**)
- [Misc] [bug] Catch RuntimeError when detecting backends for better compatibility (1647) (by **彭于斌**)
- [workflow] Add Mac OS X to Github CI (1649) (by **彭于斌**)
- [Example] Add cg_possion.py, a Poisson solver based on conjugate gradients (1595) (by **彭于斌**)
- [Refactor] "x.snode()" is deprecated, use "x.snode" instead (1654) (by **彭于斌**)
- [GUI] Support gui.fps_limit and reduce idle power consumption (1611) (by **彭于斌**)
- [GUI] Support images with 2 channels (RG) in GUI.set_image (1624) (by **彭于斌**)
- [Opt] Improve the binary ops simplify pass (1646) (by **xumingkuan**)
- [benchmark] Fix test_test.py benchmark including '<lambda>' in filename (1650) (by **彭于斌**)
- [cc] [workflow] Add C backend to Github CI (1643) (by **彭于斌**)
- [Doc] Replace fields of xxx by xxx field (1599) (by **Xudong Feng**)
- [cc] Compose ActionRecorder outputs into a single C file for Emscripten (1629) (by **彭于斌**)
- [error] Better error messages when using wrong type annotations (1612) (by **彭于斌**)
- [doc] Update instructions for using Stop Motion OBJ with PLY sequences (1638) (by **Justin**)
- [Doc] Replace "tensor" by "field" in documentation (1633) (by **Xudong Feng**)
- [doc] Fix typo in faq.rst (1636) (by **Danni**)
- Fix hyperlink in faq.rst (1637) (by **Danni**)
- [Example] Enhance stable_fluid.py with BFECC, RK2, RK3 and Taichi's new syntax (1617) (by **彭于斌**)
- [GUI] Support gui.arrow() and gui.arrows() (1625) (by **彭于斌**)
- [Lang] Support float and int as aliases for default-precision data types (1585) (by **彭于斌**)
- [Bug] Fix random side-effect causing SSA violation in ti.Vector (1631) (by **彭于斌**)
- [infra] Support GCC as compiler for Taichi developers (experimental) (1598) (by **彭于斌**)
- [Doc] Improve type.rst readability (1618) (by **彭于斌**)
- [gui] [bug] Fix hex_to_rgb (1630) (by **Yuanming Hu**)
- [async] Clone offloaded tasks lazily by maintaining a cached template task (1619) (by **Ye Kuang**)