Optimization defeated by merging module into main
I have a library, TheModule, and an application that uses TheModule, called Main. When TheModule lives in TheModule.hs and Main lives in Main.hs, optimization works as expected. When I copy all of TheModule's definitions and all of Main's definitions into Both.hs, much less optimization occurs, as can be seen from -ddump-simpl, as well as the drastic difference in running times.
The program performs a lot of small matrix-vector multiplications. The single command line argument tells how many to do.
time ./Main 1000000
20.0 :. (59.0 :. (100.0 :. (137.0 :. ())))
real 0m0.389s
user 0m0.152s
sys 0m0.232s
time ./Both 100000
20.0 :. (59.0 :. (100.0 :. (137.0 :. ())))
real 0m3.462s
user 0m3.368s
sys 0m0.068sSo that makes Both about 100 times slower. Compiled with -O2 and -fexcess-precision
Trac metadata
| Trac field | Value |
|---|---|
| Version | 6.8.3 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | |
| Operating system | |
| Architecture |