Fix reproducibility bug in fft5d

fft5d has been accessing FFTW directly instead of using the
Gromacs FFT interface, and while doing so the estimate flag was
not correctly set for reproducible runs. For now we have just
fixed it, but this FFTW-specific code should be removed from fft5d,
or we will likely see more fft bugs due to duplicated code paths.

Fixes #1690.

Change-Id: Ib03f7af710ed208d2824f105bd15712d32632cfa

diff --git a/src/gromacs/fft/fft5d.cpp b/src/gromacs/fft/fft5d.cpp
index 94fde316da46617bedc65f40f2117a72855e52dd..3b5bbab9e007723a4c07cd29001ac9139f86ddc5 100644 (file)
--- a/src/gromacs/fft/fft5d.cpp
+++ b/src/gromacs/fft/fft5d.cpp
@@ -1,7 +1,7 @@
 /*
  * This file is part of the GROMACS molecular simulation package.
  *
- * Copyright (c) 2009,2010,2012,2013,2014, by the GROMACS development team, led by
+ * Copyright (c) 2009,2010,2012,2013,2014,2015, by the GROMACS development team, led by
  * Mark Abraham, David van der Spoel, Berk Hess, and Erik Lindahl,
  * and including many others, as listed in the AUTHORS file in the
  * top-level source directory and at http://www.gromacs.org.
@@ -453,7 +453,14 @@ fft5d_plan fft5d_plan_3d(int NG, int MG, int KG, MPI_Comm comm[2], int flags, t_
         fprintf(debug, "Running on %d threads\n", nthreads);
     }
 
-#ifdef GMX_FFT_FFTW3                                                            /*if not FFTW - then we don't do a 3d plan but instead use only 1D plans */
+#ifdef GMX_FFT_FFTW3
+    /* Don't add more stuff here! We have already had at least one bug because we are reimplementing
+     * the low-level FFT interface instead of using the Gromacs FFT module. If we need more
+     * generic functionality it is far better to extend the interface so we can use it for
+     * all FFT libraries instead of writing FFTW-specific code here.
+     */
+
+    /*if not FFTW - then we don't do a 3d plan but instead use only 1D plans */
     /* It is possible to use the 3d plan with OMP threads - but in that case it is not allowed to be called from
      * within a parallel region. For now deactivated. If it should be supported it has to made sure that
      * that the execute of the 3d plan is in a master/serial block (since it contains it own parallel region)
@@ -466,10 +473,9 @@ fft5d_plan fft5d_plan_3d(int NG, int MG, int KG, MPI_Comm comm[2], int flags, t_
         int inNG = NG, outMG = MG, outKG = KG;
 
         FFTW_LOCK;
-        if (!(flags&FFT5D_NOMEASURE))
-        {
-            fftwflags |= FFTW_MEASURE;
-        }
+
+        fftwflags |= (flags & FFT5D_NOMEASURE) ? FFTW_ESTIMATE : FFTW_MEASURE;
+
         if (flags&FFT5D_REALCOMPLEX)
         {
             if (!(flags&FFT5D_BACKWARD))        /*input pointer is not complex*/