Dear R-devel Team, I'm developing a neuroscience signal pipeline package in R (https://github.com/dipterix/ravetools) and I noticed a weird issue that failed my unit test.
Basically I was trying to use `fftw3` library to implement fast multivariate fft function in C++. When I tried to compare my results with stats::fft, the test result showed the first element of **expected** (which was produced by stats::fft) was zero, which, I am pretty sure, is wrong, and I can confirm that my function produces correct results. However, somehow I couldn’t reproduce this issue on my personal computer (osx, M1, R4.1.1), the error simply went away. The catch is my function produced consistent and correct results but stats::fft was not. This does not mean `stats::fft` has bugs. Instead, I suspect there could be some weird interactions between my code and stats::fft at C/C++ level, but I couldn’t figure it out why. +++ Details: Here’s the code I used for the test: https://github.com/dipterix/ravetools/blob/4dc35d64763304aff869d92dddad38a7f2b30637/tests/testthat/test-fftw.R#L33-L41 ————————Test code———————— set.seed(1) x <- rnorm(1000) dim(x) <- c(100,10) a <- ravetools:::mvfftw_r2c(x, 0) c <- apply(x, 2, stats::fft)[1:51,] expect_equal(a, c) ———————————————————————— Here are the tests that gave me the errors: The test logs on win-builder https://win-builder.r-project.org/07586ios8AbL/00check.log Test logs on GitHub https://github.com/dipterix/ravetools/runs/3944874310?check_suite_focus=true —————————————— Failed tests —————————————— -- Failure (test-fftw.R:41:3): mvfftw_r2c -------------------------------------- `a` (`actual`) not equal to `c` (`expected`). actual vs expected [,1] [,2] [,3] [,4] ... - actual[1, ] 10.8887367+ 0.0000000i -3.7808077+ 0.0000000i 2.967354+ 0.000000i 5.160186+ 0.000000i ... + expected[1, ] 0.0000000+ 0.0000000i -3.7808077+ 0.0000000i 2.967354+ 0.000000i 5.160186+ 0.000000i... ———————————————————————— The first columns are different, `actual` is the results I produced via `ravetools:::mvfftw_r2c`, and `expected` was produced by `stats::fft` Any help or attention is very much appreciated. Thanks, - Zhengjia ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
