| Commit message (Collapse) | Author | Age | Files | Lines | |
|---|---|---|---|---|---|
| * | 3413 | Kartik K. Agaram | 2016-09-24 | 1 | -2/+5 |
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| * | 3288 - cleaner heuristic for cleaving | Kartik K. Agaram | 2016-08-31 | 1 | -10/+6 |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | For the last couple of days I've been implicitly thinking in terms of how many compilation units I want to generate. Might as well make that explicit and drop the hacky ideas for approximating it. I tried more timing experiments like the ones in commit 3281. Conclusion: I can't have the best of both worlds: 1. Full compilation doesn't take too much longer than with a single compilation unit. 2. Incremental compilation is fast enough that there's negligible benefit from dropping optimization. We're still taking on a 10s hit in full build time. I care more about not degrading the full compilation too much, since that gets magnified so much on the Couch's puny server. So we'll just have to continue using CXXFLAGS=-g when we care to save a few seconds in incremental compilation time. A final mystery: the build time increases by 10s with the new heuristic even though the number of calls to the compiler (and therefore the fixed cost) is the same. Seems like separating certain functions into different units is causing the compiler issues. Dropping from 4 to 3 compilation units eliminated the issue. --- Appendix: Measurements before: full build 4 + test: 42s incremental compilation with -O3: varied from 30s for mu_0.cc to 5s for mu_3.cc longer times benefitted from dropping -O3 after: full build 1 + test: 39s full build 2 + test: 41s full build 3 + test: 43s full build 4 + test: 52s full build 5 + test: 53s full build 6 + test: 51s full build 10 (9) + test: 54s full build 20 (16) + test: 58s | ||||
| * | 3284 | Kartik K. Agaram | 2016-08-30 | 1 | -6/+6 |
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| * | 3281 - faster incremental builds for layers | Kartik K. Agaram | 2016-08-29 | 1 | -0/+244 |
| Before: layers -> tangle -> g++ All changes to (C++) layers triggered recompilation of everything, taking 35s on my laptop, and over 4 minutes on a puny server with just 512MB of RAM. After: layers -> tangle -> cleave -> g++ Now a tiny edit takes just 5s to recompile on my laptop. My initial approach was to turn each function into a separate compilation unit under the .build/ directory. That blew up the time for a full/initial compilation to almost 6 minutes on my laptop. Trial and error showed 4 compilation units to be close to the sweet spot. Full compilation is still slightly slower (43s) but not by much. I could speed things up further by building multiple of the compilation units in parallel (the recursive invocation in 'makefile'). But that would put more pressure on a puny server, so I'm going to avoid getting too aggressive. --- Other considerations I spent some time manually testing the dependency structure to the makefile, making sure that files aren't unnecessarily written to disk, modifying their timestamp and triggering dependent work; that changes to layers don't unnecessarily modify the common headers or list of globals; that changes to the cleave/ tool itself rebuild the entire project; that the old auto-generated '_list' files plug in at the right stage in the pipeline; that changes to common headers trigger recompilation of everything; etc. Too bad it's not easy to write some tests for all this. I spent some time trying to make sure the makefile was not too opaque to a newcomer. The targets mostly flow from top to bottom. There's a little diagram at the top that is hopefully illuminating. When I had 700 compilation units for 700 functions I stopped printing each one of those compilation commands, but when I backed off to just 4 compilation units I decided to err on the side of making the build steps easy to see. | |||||