Written: 2021-07-09 19:23 +0000
Project scaffolding and compiler design
This post is part of a series based around my weekly GSoC21 project check-ins.
GSoC21 W5: LFortran Design Details and
minidftatom<– You are here!
- Met with Ondrej on Tuesday, Wednesday and Thursday
- Discussed the AST, ASR and backends in more detail
- Zeroed in on several alternate designs implementations of intrinsic functions
- We have prototype calls for the two kinds of compile evaluation
sinimplementation (pre-GSoC21) is pretty unwieldy and a cleaner method which we elected to pursue is the
- Discussed concrete methods of working
- Talked about the runtime library
- This is a late stage issue, after the ASR generation
This week focused around a subset of
dftatom which Ondrej prepared. In fact the main highlight was working through possible code design directions and iterating on these with Ondrej (and Gagandeep asynchrously) to come up with the intrinsic function design methods and the compile time evaluation of expressions plan issue (discussed below in issue 420).
New Merge Requests
- Restructuring of the ASR (1024)
- A code cleanup task, to reduce code smell from
usingstatements and to refactor into more logical file structures
- Grammar modifications (1037)
- Name changes to keep a consistent clear implementation structure
Freshly Assigned Issues
- minidftatom Roadmap (401)
- A clone of the
- size() not handled correctly for arrays (416)
- This is an ASR bug, with a fix which should not be too difficult to track down
- Compile time evaluation of expressions (420)
- This is an internal implementation design specification document, which essentially introduces a
valueoption for the ASR
Continue down the road for
401 and also consider perhaps, more runtime library logic.
Since running on a new project is roughly similar, I will only briefly go over the steps.
1git clone email@example.com:lfortran/examples/minidftatom.git 2cd minidftatom 3FC=gfortran cmake . 4make -j$(nproc) 5./F_atom_U
1 Z= 92 N= 5500 2E_tot= -25658.417889 3 state E occupancy 41s -3689.355140 2.000 52s -639.778728 2.000 62p -619.108550 6.000 73s -161.118073 2.000 83p -150.978980 6.000 93d -131.977358 10.000 104s -40.528084 2.000 114p -35.853321 6.000 124d -27.123212 10.000 134f -15.027460 14.000 145s -8.824089 2.000 155p -7.018092 6.000 165d -3.866175 10.000 175f -0.366543 3.000 186s -1.325976 2.000 196p -0.822538 6.000 206d -0.143190 1.000 217s -0.130948 2.000 22 Print the first 10 values of the 1st and 2nd orbitals: 23 1753.2892641883584 1753.2812175211841 1753.2731512531607 1753.2650645481160 1753.2569495840532 1753.2488203554758 1753.2406710770906 1753.2325014795395 1753.2243110250588 1753.2160993495806 24 587.50702296395195 587.50432661503442 587.50162369317059 587.49891391928361 587.49619467268258 587.49347064291044 587.49073989144335 587.48800232804547 587.48525777252200 587.48250610287175
Parsing and AST Generation
The test for the parser is essentially to check if the output before and after formatting with
lfortran still compiles to the same result.
Note that because of the nature of this, we need to ensure
-ffree-line-length-none is passed when working with the
1cd minidftatom 2# -i --> Inplace modification 3for file in *.f90; do lfortran fmt -i $file; done 4make clean 5FC=gfortran cmake . 6make -j$(nproc) 7./F_atom_U
Before going on to the ASR, a dependency tree is required. As before, it is reproduced in excruciating detail in the issue, and represented by a pretty picture shown in Fig. mdftatomgit for this post.
1pip install fortdepend 2cd minidftatom/src 3fortdepend -g -c
I found a new favorite command, which I should have remembered while it was being implemented (by Thirumalai Shaktivel in 765); namely the
--indent option which makes for a much more readable ASR output. Apart from that
git diff --color-words works well enough as well.
The main work plan outcomes for the week were the new design specifications for the compile time evaluation of expressions. It is always an enriching experience to work with Ondrej directly (even over the ether) and this week felt more productive than most. I hope to keep the same momentum going. This will allow faster progress on the main issue of getting ASR generated for