4 files changed, 92 insertions, 17 deletions
diff --git a/gr-fft/include/gnuradio/fft/fft_vcc.h b/gr-fft/include/gnuradio/fft/fft_vcc.h
index 1e09521b4f..28f6d1d0d4 100644
--- a/gr-fft/include/gnuradio/fft/fft_vcc.h
+++ b/gr-fft/include/gnuradio/fft/fft_vcc.h
@@ -1,6 +1,6 @@
 /* -*- c++ -*- */
 /*
- * Copyright 2004,2007,2008,2012 Free Software Foundation, Inc.
+ * Copyright 2004,2007,2008,2012,2018 Free Software Foundation, Inc.
  *
  * This file is part of GNU Radio
  *
@@ -32,6 +32,29 @@ namespace gr {
     /*!
      * \brief Compute forward or reverse FFT. complex vector in / complex vector out.
      * \ingroup fourier_analysis_blk
+     *
+     * The FFT operation is defined for a vector \f$x\f$ with \f$N\f$ uniformly
+     * sampled points by
+     *
+     * \f[ X(a) = \sum_{k=0}^{N-1} x(a) \cdot e^{-j 2\pi k a / N} \f]
+     *
+     * \f$ X = FFT\{x\} \f$ is the the FFT transform of \f$x(a)\f$, \f$j\f$ is
+     * the imaginary unit, \f$k\f$ and \f$a\f$ range from \f$0\f$ to \f$N-1\f$.
+     *
+     * The IFFT operation is defined for a vector \f$y\f$ with \f$N\f$
+     * uniformly sampled points by
+     *
+     * \f[ Y(b) = \sum_{k=0}^{N-1} y(b) \cdot e^{j 2\pi k b / N} \f]
+     *
+     * \f$Y = IFFT\{y\}\f$ is the the inverse FFT transform of \f$y(b)\f$,
+     * \f$j\f$ is the imaginary unit, \f$k\f$ and \f$b\f$ range from \f$0\f$ to
+     * \f$N-1\f$.
+     *
+     * \b Note, that due to the underlying FFTW library, the output of a FFT
+     * followed by an IFFT (or the other way arround) will be scaled i.e.
+     * \f$FFT\{ \, IFFT\{x\} \,\} =  N \cdot x \neq x\f$.
+     *
+     * \see http://www.fftw.org/faq/section3.html#whyscaled
      */
     class FFT_API fft_vcc : virtual public sync_block
     {
@@ -39,7 +62,13 @@ namespace gr {
 
       // gr::fft::fft_vcc::sptr
       typedef boost::shared_ptr<fft_vcc> sptr;
-
+      /*! \brief
+       * \param[in] fft_size N.
+       * \param[in] forward True performs FFT, False performs IFFT.
+       * \param[in] window Window function to be used.
+       * \param[in] shifted True moves DC carrier to the middle.
+       * \param[in] nthreads Number of underlying threads.
+       */
       static sptr make(int fft_size, bool forward,
                        const std::vector<float> &window,
                        bool shift=false, int nthreads=1);
diff --git a/gr-fft/include/gnuradio/fft/fft_vfc.h b/gr-fft/include/gnuradio/fft/fft_vfc.h
index 91ed81fb17..5639465ab5 100644
--- a/gr-fft/include/gnuradio/fft/fft_vfc.h
+++ b/gr-fft/include/gnuradio/fft/fft_vfc.h
@@ -1,6 +1,6 @@
 /* -*- c++ -*- */
 /*
- * Copyright 2004,2010,2012 Free Software Foundation, Inc.
+ * Copyright 2004,2010,2012,2018 Free Software Foundation, Inc.
  *
  * This file is part of GNU Radio
  *
@@ -30,16 +30,46 @@ namespace gr {
   namespace fft {
 
     /*!
-     * \brief Compute forward or reverse FFT. float vector in / complex vector out.
+     * \brief Compute forward or reverse FFT. complex vector in / complex vector out.
      * \ingroup fourier_analysis_blk
+     *
+     * The FFT operation is defined for a vector \f$x\f$ with \f$N\f$ uniformly
+     * sampled points by
+     *
+     * \f[ X(a) = \sum_{k=0}^{N-1} x(a) \cdot e^{-j 2\pi k a / N} \f]
+     *
+     * \f$ X = FFT\{x\} \f$ is the the FFT transform of \f$x(a)\f$, \f$j\f$ is
+     * the imaginary unit, \f$k\f$ and \f$a\f$ range from \f$0\f$ to \f$N-1\f$.
+     *
+     * The IFFT operation is defined for a vector \f$y\f$ with \f$N\f$
+     * uniformly sampled points by
+     *
+     * \f[ Y(b) = \sum_{k=0}^{N-1} y(b) \cdot e^{j 2\pi k b / N} \f]
+     *
+     * \f$Y = IFFT\{y\}\f$ is the the inverse FFT transform of \f$y(b)\f$,
+     * \f$j\f$ is the imaginary unit, \f$k\f$ and \f$b\f$ range from \f$0\f$ to
+     * \f$N-1\f$.
+     *
+     * \b Note, that due to the underlying FFTW library, the output of a FFT
+     * followed by an IFFT (or the other way arround) will be scaled i.e.
+     * \f$FFT\{ \, IFFT\{x\} \,\} =  N \cdot x \neq x\f$.
+     *
+     * \see http://www.fftw.org/faq/section3.html#whyscaled
      */
-    class FFT_API fft_vfc : virtual public sync_block
+   class FFT_API fft_vfc : virtual public sync_block
     {
     public:
 
       // gr::fft::fft_vfc::sptr
       typedef boost::shared_ptr<fft_vfc> sptr;
 
+      /*! \brief
+       * \param[in] fft_size N.
+       * \param[in] forward True performs FFT, False performs IFFT.
+       * \param[in] window Window function to be used.
+       * \param[in] shifted True moves DC carrier to the middle.
+       * \param[in] nthreads Number of underlying threads.
+       */
       static sptr make(int fft_size, bool forward,
 			       const std::vector<float> &window,
 			       int nthreads=1);
diff --git a/gr-fft/lib/fft.cc b/gr-fft/lib/fft.cc
index 871ad9bcaa..718cd0990f 100644
--- a/gr-fft/lib/fft.cc
+++ b/gr-fft/lib/fft.cc
@@ -56,7 +56,8 @@ namespace fs = boost::filesystem;
 namespace gr {
   namespace fft {
     static boost::mutex wisdom_thread_mutex;
-	boost::interprocess::file_lock wisdom_lock;
+    boost::interprocess::file_lock wisdom_lock;
+    static bool wisdom_lock_init_done = false; // Modify while holding 'wisdom_thread_mutex'
 
     gr_complex *
     malloc_complex(int size)
@@ -99,15 +100,36 @@ namespace gr {
     }
 
     static void
+    wisdom_lock_init()
+    {
+      if (wisdom_lock_init_done)
+        return;
+
+      const std::string wisdom_lock_file = wisdom_filename() + ".lock";
+      // std::cerr << "Creating FFTW wisdom lockfile: " << wisdom_lock_file << std::endl;
+      int fd = open(wisdom_lock_file.c_str(),
+        O_WRONLY | O_CREAT | O_NOCTTY | O_NONBLOCK,
+        0666);
+      if (fd < 0) {
+        throw std::runtime_error("Failed to create FFTW wisdom lockfile: " + wisdom_lock_file);
+      }
+      close(fd);
+      wisdom_lock = boost::interprocess::file_lock(wisdom_lock_file.c_str());
+      wisdom_lock_init_done = true;
+    }
+
+    static void
     lock_wisdom()
     {
-	  wisdom_thread_mutex.lock(); 
-	  wisdom_lock.lock();
+      wisdom_thread_mutex.lock();
+      wisdom_lock_init();
+      wisdom_lock.lock();
     }
 
     static void
     unlock_wisdom()
     {
+      // Assumes 'lock_wisdom' has already been called (i.e. this file_lock is valid)
       wisdom_lock.unlock();
       wisdom_thread_mutex.unlock();
     }
@@ -163,15 +185,6 @@ namespace gr {
     {
       // Hold global mutex during plan construction and destruction.
       planner::scoped_lock lock(planner::mutex());
-	  const std::string wisdom_lock_file = wisdom_filename() + ".lock";
-	  int fd = open(wisdom_lock_file.c_str(),
-		  O_WRONLY | O_CREAT | O_NOCTTY | O_NONBLOCK,
-		  0666);
-	  if (fd < 0) {
-		  throw std::exception();
-	  }
-	  close(fd);
-	  wisdom_lock = boost::interprocess::file_lock(wisdom_lock_file.c_str());
 
       assert (sizeof (fftwf_complex) == sizeof (gr_complex));
 
diff --git a/gr-fft/python/fft/CMakeLists.txt b/gr-fft/python/fft/CMakeLists.txt
index f08aebc11d..acf81ca050 100644
--- a/gr-fft/python/fft/CMakeLists.txt
+++ b/gr-fft/python/fft/CMakeLists.txt
@@ -35,6 +35,9 @@ if(ENABLE_TESTING)
   set(GR_TEST_LIBRARY_DIRS "")
   set(GR_TEST_PYTHON_DIRS
     ${CMAKE_BINARY_DIR}/gnuradio-runtime/python
+    ${CMAKE_BINARY_DIR}/gnuradio-runtime/swig	
+    ${CMAKE_BINARY_DIR}/gr-blocks/swig		
+    ${CMAKE_BINARY_DIR}/gr-fft/swig		
     )
   include(GrTest)
   file(GLOB py_qa_test_files "qa_*.py")