Merge pull request #28 from dmpelt/projector3d-python

Add projector3d and CUDA projectors to Python (to match new Matlab code)

11 files changed, 391 insertions, 64 deletions

diff --git a/python/astra/ASTRAProjector.py b/python/astra/ASTRAProjector.py
index 96acb10..f282618 100644
--- a/python/astra/ASTRAProjector.py
+++ b/python/astra/ASTRAProjector.py
@@ -70,11 +70,9 @@ class ASTRAProjector2D(object):
     :type vol_geom: :class:`dict`
     :param proj_type: Projector type, such as ``'line'``, ``'linear'``, ...
     :type proj_type: :class:`string`
-    :param useCUDA: If ``True``, use CUDA for calculations, when possible.
-    :type useCUDA: :class:`bool`
     """
 
-    def __init__(self, proj_geom, vol_geom, proj_type, useCUDA=False):
+    def __init__(self, proj_geom, vol_geom, proj_type):
         self.vol_geom = vol_geom
         self.recSize = vol_geom['GridColCount']
         self.angles = proj_geom['ProjectionAngles']
@@ -84,7 +82,6 @@ class ASTRAProjector2D(object):
         self.nProj = self.angles.shape[0]
         self.proj_geom = proj_geom
         self.proj_id = ac.create_projector(proj_type, proj_geom, vol_geom)
-        self.useCUDA = useCUDA
         self.T = ASTRAProjector2DTranspose(self)
 
     def backProject(self, data):
@@ -96,7 +93,7 @@ class ASTRAProjector2D(object):
 
         """
         vol_id, vol = ac.create_backprojection(
-            data, self.proj_id, useCUDA=self.useCUDA, returnData=True)
+            data, self.proj_id, returnData=True)
         data2d.delete(vol_id)
         return vol
 
@@ -108,7 +105,7 @@ class ASTRAProjector2D(object):
         :returns: :class:`numpy.ndarray` -- The forward projection.
 
         """
-        sin_id, sino = ac.create_sino(data, self.proj_id, useCUDA=self.useCUDA, returnData=True)
+        sin_id, sino = ac.create_sino(data, self.proj_id, returnData=True)
         data2d.delete(sin_id)
         return sino
 
diff --git a/python/astra/PyIncludes.pxd b/python/astra/PyIncludes.pxd
index 434546a..7df02c5 100644
--- a/python/astra/PyIncludes.pxd
+++ b/python/astra/PyIncludes.pxd
@@ -27,6 +27,8 @@ from libcpp cimport bool
 from libcpp.string cimport string
 from .PyXMLDocument cimport XMLNode
 
+include "config.pxi"
+
 cdef extern from "astra/Globals.h" namespace "astra":
 	ctypedef float float32
 	ctypedef double float64
@@ -150,6 +152,20 @@ cdef extern from "astra/Projector2D.h" namespace "astra":
 		CVolumeGeometry2D* getVolumeGeometry()
 		CSparseMatrix* getMatrix()
 
+cdef extern from "astra/Projector3D.h" namespace "astra":
+	cdef cppclass CProjector3D:
+		bool isInitialized()
+		CProjectionGeometry3D* getProjectionGeometry()
+		CVolumeGeometry3D* getVolumeGeometry()
+
+IF HAVE_CUDA==True:
+	cdef extern from "astra/CudaProjector3D.h" namespace "astra":
+		cdef cppclass CCudaProjector3D
+
+	cdef extern from "astra/CudaProjector2D.h" namespace "astra":
+		cdef cppclass CCudaProjector2D
+
+
 cdef extern from "astra/SparseMatrix.h" namespace "astra":
 	cdef cppclass CSparseMatrix:
 		CSparseMatrix(unsigned int,unsigned int,unsigned long)
diff --git a/python/astra/PyProjector3DFactory.pxd b/python/astra/PyProjector3DFactory.pxd
new file mode 100644
index 0000000..bcbce94
--- /dev/null
+++ b/python/astra/PyProjector3DFactory.pxd
@@ -0,0 +1,35 @@
+#-----------------------------------------------------------------------
+#Copyright 2013 Centrum Wiskunde & Informatica, Amsterdam
+#
+#Author: Daniel M. Pelt
+#Contact: D.M.Pelt@cwi.nl
+#Website: http://dmpelt.github.io/pyastratoolbox/
+#
+#
+#This file is part of the Python interface to the
+#All Scale Tomographic Reconstruction Antwerp Toolbox ("ASTRA Toolbox").
+#
+#The Python interface to the ASTRA Toolbox is free software: you can redistribute it and/or modify
+#it under the terms of the GNU General Public License as published by
+#the Free Software Foundation, either version 3 of the License, or
+#(at your option) any later version.
+#
+#The Python interface to the ASTRA Toolbox is distributed in the hope that it will be useful,
+#but WITHOUT ANY WARRANTY; without even the implied warranty of
+#MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+#GNU General Public License for more details.
+#
+#You should have received a copy of the GNU General Public License
+#along with the Python interface to the ASTRA Toolbox. If not, see <http://www.gnu.org/licenses/>.
+#
+#-----------------------------------------------------------------------
+from libcpp.string cimport string
+from libcpp cimport bool
+from .PyIncludes cimport *
+
+cdef extern from "astra/AstraObjectFactory.h" namespace "astra":
+    cdef cppclass CProjector3DFactory:
+        CProjector3D *create(Config)
+
+cdef extern from "astra/AstraObjectFactory.h" namespace "astra::CProjector3DFactory":
+    cdef CProjector3DFactory* getSingletonPtr()
diff --git a/python/astra/PyProjector3DManager.pxd b/python/astra/PyProjector3DManager.pxd
new file mode 100644
index 0000000..b1eac6b
--- /dev/null
+++ b/python/astra/PyProjector3DManager.pxd
@@ -0,0 +1,39 @@
+#-----------------------------------------------------------------------
+#Copyright 2013 Centrum Wiskunde & Informatica, Amsterdam
+#
+#Author: Daniel M. Pelt
+#Contact: D.M.Pelt@cwi.nl
+#Website: http://dmpelt.github.io/pyastratoolbox/
+#
+#
+#This file is part of the Python interface to the
+#All Scale Tomographic Reconstruction Antwerp Toolbox ("ASTRA Toolbox").
+#
+#The Python interface to the ASTRA Toolbox is free software: you can redistribute it and/or modify
+#it under the terms of the GNU General Public License as published by
+#the Free Software Foundation, either version 3 of the License, or
+#(at your option) any later version.
+#
+#The Python interface to the ASTRA Toolbox is distributed in the hope that it will be useful,
+#but WITHOUT ANY WARRANTY; without even the implied warranty of
+#MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+#GNU General Public License for more details.
+#
+#You should have received a copy of the GNU General Public License
+#along with the Python interface to the ASTRA Toolbox. If not, see <http://www.gnu.org/licenses/>.
+#
+#-----------------------------------------------------------------------
+from libcpp.string cimport string
+
+from .PyIncludes cimport *
+
+cdef extern from "astra/AstraObjectManager.h" namespace "astra":
+    cdef cppclass CProjector3DManager:
+        string info()
+        void clear()
+        void remove(int i)
+        int store(CProjector3D *)
+        CProjector3D * get(int i)
+
+cdef extern from "astra/AstraObjectManager.h" namespace "astra::CProjector3DManager":
+    cdef CProjector3DManager* getSingletonPtr()
diff --git a/python/astra/__init__.py b/python/astra/__init__.py
index a61aafc..c249c01 100644
--- a/python/astra/__init__.py
+++ b/python/astra/__init__.py
@@ -33,6 +33,7 @@ from . import astra
 from . import data3d
 from . import algorithm
 from . import projector
+from . import projector3d
 from . import matrix
 
 import os
diff --git a/python/astra/creators.py b/python/astra/creators.py
index 9aba464..68bc8a2 100644
--- a/python/astra/creators.py
+++ b/python/astra/creators.py
@@ -30,15 +30,16 @@ import math
 from . import data2d
 from . import data3d
 from . import projector
+from . import projector3d
 from . import algorithm
 
 def astra_dict(intype):
     """Creates a dict to use with the ASTRA Toolbox.
-    
+
     :param intype: Type of the ASTRA object.
     :type intype: :class:`string`
     :returns: :class:`dict` -- An ASTRA dict of type ``intype``.
-    
+
     """
     if intype == 'SIRT_CUDA2':
         intype = 'SIRT_CUDA'
@@ -255,25 +256,23 @@ This method can be called in a number of ways:
             raise Exception('not enough variables: astra_create_proj_geom(parallel3d_vec, det_row_count, det_col_count, V)')
         if not args[2].shape[1] == 12:
             raise Exception('V should be a Nx12 matrix, with N the number of projections')
-        return {'type': 'parallel3d_vec','DetectorRowCount':args[0],'DetectorColCount':args[1],'Vectors':args[2]}    
+        return {'type': 'parallel3d_vec','DetectorRowCount':args[0],'DetectorColCount':args[1],'Vectors':args[2]}
     elif intype == 'sparse_matrix':
         if len(args) < 4:
             raise Exception(
                 'not enough variables: astra_create_proj_geom(sparse_matrix, det_width, det_count, angles, matrix_id)')
         return {'type': 'sparse_matrix', 'DetectorWidth': args[0], 'DetectorCount': args[1], 'ProjectionAngles': args[2], 'MatrixID': args[3]}
     else:
-        raise Exception('Error: unknown type ' + intype) 
+        raise Exception('Error: unknown type ' + intype)
 
 
-def create_backprojection(data, proj_id, useCUDA=False, returnData=True):
+def create_backprojection(data, proj_id, returnData=True):
     """Create a backprojection of a sinogram (2D).
 
 :param data: Sinogram data or ID.
 :type data: :class:`numpy.ndarray` or :class:`int`
 :param proj_id: ID of the projector to use.
 :type proj_id: :class:`int`
-:param useCUDA: If ``True``, use CUDA for the calculation.
-:type useCUDA: :class:`bool`
 :param returnData: If False, only return the ID of the backprojection.
 :type returnData: :class:`bool`
 :returns: :class:`int` or (:class:`int`, :class:`numpy.ndarray`) -- If ``returnData=False``, returns the ID of the backprojection. Otherwise, returns a tuple containing the ID of the backprojection and the backprojection itself, in that order.
@@ -287,13 +286,13 @@ def create_backprojection(data, proj_id, useCUDA=False, returnData=True):
         sino_id = data
     vol_id = data2d.create('-vol', vol_geom, 0)
 
-    algString = 'BP'
-    if useCUDA:
-        algString = algString + '_CUDA'
+    if projector.is_cuda(proj_id):
+        algString = 'BP_CUDA'
+    else:
+        algString = 'BP'
 
     cfg = astra_dict(algString)
-    if not useCUDA:
-        cfg['ProjectorId'] = proj_id
+    cfg['ProjectorId'] = proj_id
     cfg['ProjectionDataId'] = sino_id
     cfg['ReconstructionDataId'] = vol_id
     alg_id = algorithm.create(cfg)
@@ -345,20 +344,13 @@ def create_backprojection3d_gpu(data, proj_geom, vol_geom, returnData=True):
         return vol_id
 
 
-def create_sino(data, proj_id=None, proj_geom=None, vol_geom=None,
-                useCUDA=False, returnData=True, gpuIndex=None):
+def create_sino(data, proj_id, returnData=True, gpuIndex=None):
     """Create a forward projection of an image (2D).
 
     :param data: Image data or ID.
     :type data: :class:`numpy.ndarray` or :class:`int`
     :param proj_id: ID of the projector to use.
     :type proj_id: :class:`int`
-    :param proj_geom: Projection geometry.
-    :type proj_geom: :class:`dict`
-    :param vol_geom: Volume geometry.
-    :type vol_geom: :class:`dict`
-    :param useCUDA: If ``True``, use CUDA for the calculation.
-    :type useCUDA: :class:`bool`
     :param returnData: If False, only return the ID of the forward projection.
     :type returnData: :class:`bool`
     :param gpuIndex: Optional GPU index.
@@ -369,36 +361,21 @@ def create_sino(data, proj_id=None, proj_geom=None, vol_geom=None,
     projection. Otherwise, returns a tuple containing the ID of the
     forward projection and the forward projection itself, in that
     order.
-
-    The geometry of setup is defined by ``proj_id`` or with
-    ``proj_geom`` and ``vol_geom``. If ``proj_id`` is given, then
-    ``proj_geom`` and ``vol_geom`` must be None and vice versa.
 """
-    if proj_id is not None:
-        proj_geom = projector.projection_geometry(proj_id)
-        vol_geom = projector.volume_geometry(proj_id)
-    elif proj_geom is not None and vol_geom is not None:
-        if not useCUDA:
-            # We need more parameters to create projector.
-            raise ValueError(
-                """A ``proj_id`` is needed when CUDA is not used.""")
-    else:
-        raise Exception("""The geometry setup is not defined.
-        The geometry of setup is defined by ``proj_id`` or with
-        ``proj_geom`` and ``vol_geom``. If ``proj_id`` is given, then
-        ``proj_geom`` and ``vol_geom`` must be None and vice versa.""")
+    proj_geom = projector.projection_geometry(proj_id)
+    vol_geom = projector.volume_geometry(proj_id)
 
     if isinstance(data, np.ndarray):
         volume_id = data2d.create('-vol', vol_geom, data)
     else:
         volume_id = data
     sino_id = data2d.create('-sino', proj_geom, 0)
-    algString = 'FP'
-    if useCUDA:
-        algString = algString + '_CUDA'
+    if projector.is_cuda(proj_id):
+        algString = 'FP_CUDA'
+    else:
+        algString = 'FP'
     cfg = astra_dict(algString)
-    if not useCUDA:
-        cfg['ProjectorId'] = proj_id
+    cfg['ProjectorId'] = proj_id
     if gpuIndex is not None:
         cfg['option'] = {'GPUindex': gpuIndex}
     cfg['ProjectionDataId'] = sino_id
@@ -496,8 +473,7 @@ def create_reconstruction(rec_type, proj_id, sinogram, iterations=1, use_mask='n
     vol_geom = projector.volume_geometry(proj_id)
     recon_id = data2d.create('-vol', vol_geom, 0)
     cfg = astra_dict(rec_type)
-    if not 'CUDA' in rec_type:
-        cfg['ProjectorId'] = proj_id
+    cfg['ProjectorId'] = proj_id
     cfg['ProjectionDataId'] = sino_id
     cfg['ReconstructionDataId'] = recon_id
     cfg['options'] = {}
@@ -560,4 +536,8 @@ def create_projector(proj_type, proj_geom, vol_geom):
     cfg = astra_dict(proj_type)
     cfg['ProjectionGeometry'] = proj_geom
     cfg['VolumeGeometry'] = vol_geom
-    return projector.create(cfg)
+    types3d = ['linear3d', 'linearcone', 'cuda3d']
+    if proj_type in types3d:
+        return projector3d.create(cfg)
+    else:
+        return projector.create(cfg)
diff --git a/python/astra/projector.py b/python/astra/projector.py
index c916c52..e370e5a 100644
--- a/python/astra/projector.py
+++ b/python/astra/projector.py
@@ -27,21 +27,21 @@ from . import projector_c as p
 
 def create(config):
     """Create projector object.
-    
+
     :param config: Projector options.
     :type config: :class:`dict`
     :returns: :class:`int` -- the ID of the constructed object.
-    
+
     """
     return p.create(config)
 
 
 def delete(ids):
     """Delete a projector object.
-    
+
     :param ids: ID or list of ID's to delete.
     :type ids: :class:`int` or :class:`list`
-    
+
     """
     return p.delete(ids)
 
@@ -57,22 +57,22 @@ def info():
 
 def projection_geometry(i):
     """Get projection geometry of a projector.
-    
+
     :param i: ID of projector.
     :type i: :class:`int`
     :returns: :class:`dict` -- projection geometry
-    
+
     """
     return p.projection_geometry(i)
 
 
 def volume_geometry(i):
     """Get volume geometry of a projector.
-    
+
     :param i: ID of projector.
     :type i: :class:`int`
     :returns: :class:`dict` -- volume geometry
-    
+
     """
     return p.volume_geometry(i)
 
@@ -88,13 +88,23 @@ def weights_projection(i, projection_index):
 def splat(i, row, col):
     return p.splat(i, row, col)
 
+def is_cuda(i):
+    """Check whether a projector is a CUDA projector.
+
+    :param i: ID of projector.
+    :type i: :class:`int`
+    :returns: :class:`bool` -- True if the projector is a CUDA projector.
+
+    """
+    return p.is_cuda(i)
+
 
 def matrix(i):
     """Get sparse matrix of a projector.
-    
+
     :param i: ID of projector.
     :type i: :class:`int`
     :returns: :class:`int` -- ID of sparse matrix.
-    
+
     """
     return p.matrix(i)
diff --git a/python/astra/projector3d.py b/python/astra/projector3d.py
new file mode 100644
index 0000000..d1086b9
--- /dev/null
+++ b/python/astra/projector3d.py
@@ -0,0 +1,100 @@
+#-----------------------------------------------------------------------
+#Copyright 2013 Centrum Wiskunde & Informatica, Amsterdam
+#
+#Author: Daniel M. Pelt
+#Contact: D.M.Pelt@cwi.nl
+#Website: http://dmpelt.github.io/pyastratoolbox/
+#
+#
+#This file is part of the Python interface to the
+#All Scale Tomographic Reconstruction Antwerp Toolbox ("ASTRA Toolbox").
+#
+#The Python interface to the ASTRA Toolbox is free software: you can redistribute it and/or modify
+#it under the terms of the GNU General Public License as published by
+#the Free Software Foundation, either version 3 of the License, or
+#(at your option) any later version.
+#
+#The Python interface to the ASTRA Toolbox is distributed in the hope that it will be useful,
+#but WITHOUT ANY WARRANTY; without even the implied warranty of
+#MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+#GNU General Public License for more details.
+#
+#You should have received a copy of the GNU General Public License
+#along with the Python interface to the ASTRA Toolbox. If not, see <http://www.gnu.org/licenses/>.
+#
+#-----------------------------------------------------------------------
+from . import projector3d_c as p
+
+def create(config):
+    """Create projector object.
+
+    :param config: Projector options.
+    :type config: :class:`dict`
+    :returns: :class:`int` -- the ID of the constructed object.
+
+    """
+    return p.create(config)
+
+
+def delete(ids):
+    """Delete a projector object.
+
+    :param ids: ID or list of ID's to delete.
+    :type ids: :class:`int` or :class:`list`
+
+    """
+    return p.delete(ids)
+
+
+def clear():
+    """Clear all projector objects."""
+    return p.clear()
+
+
+def info():
+    """Print info on projector objects in memory."""
+    return p.info()
+
+def projection_geometry(i):
+    """Get projection geometry of a projector.
+
+    :param i: ID of projector.
+    :type i: :class:`int`
+    :returns: :class:`dict` -- projection geometry
+
+    """
+    return p.projection_geometry(i)
+
+
+def volume_geometry(i):
+    """Get volume geometry of a projector.
+
+    :param i: ID of projector.
+    :type i: :class:`int`
+    :returns: :class:`dict` -- volume geometry
+
+    """
+    return p.volume_geometry(i)
+
+
+def weights_single_ray(i, projection_index, detector_index):
+    return p.weights_single_ray(i, projection_index, detector_index)
+
+
+def weights_projection(i, projection_index):
+    return p.weights_projection(i, projection_index)
+
+
+def splat(i, row, col):
+    return p.splat(i, row, col)
+
+
+def is_cuda(i):
+    """Check whether a projector is a CUDA projector.
+
+    :param i: ID of projector.
+    :type i: :class:`int`
+    :returns: :class:`bool` -- True if the projector is a CUDA projector.
+
+    """
+    return p.is_cuda(i)
diff --git a/python/astra/projector3d_c.pyx b/python/astra/projector3d_c.pyx
new file mode 100644
index 0000000..8b978d7
--- /dev/null
+++ b/python/astra/projector3d_c.pyx
@@ -0,0 +1,119 @@
+#-----------------------------------------------------------------------
+#Copyright 2013 Centrum Wiskunde & Informatica, Amsterdam
+#
+#Author: Daniel M. Pelt
+#Contact: D.M.Pelt@cwi.nl
+#Website: http://dmpelt.github.io/pyastratoolbox/
+#
+#
+#This file is part of the Python interface to the
+#All Scale Tomographic Reconstruction Antwerp Toolbox ("ASTRA Toolbox").
+#
+#The Python interface to the ASTRA Toolbox is free software: you can redistribute it and/or modify
+#it under the terms of the GNU General Public License as published by
+#the Free Software Foundation, either version 3 of the License, or
+#(at your option) any later version.
+#
+#The Python interface to the ASTRA Toolbox is distributed in the hope that it will be useful,
+#but WITHOUT ANY WARRANTY; without even the implied warranty of
+#MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+#GNU General Public License for more details.
+#
+#You should have received a copy of the GNU General Public License
+#along with the Python interface to the ASTRA Toolbox. If not, see <http://www.gnu.org/licenses/>.
+#
+#-----------------------------------------------------------------------
+# distutils: language = c++
+# distutils: libraries = astra
+
+import six
+from .PyIncludes cimport *
+
+cimport utils
+from .utils import wrap_from_bytes
+
+cimport PyProjector3DFactory
+from .PyProjector3DFactory cimport CProjector3DFactory
+
+cimport PyProjector3DManager
+from .PyProjector3DManager cimport CProjector3DManager
+
+cimport PyXMLDocument
+from .PyXMLDocument cimport XMLDocument
+
+cdef CProjector3DManager * manProj = <CProjector3DManager * >PyProjector3DManager.getSingletonPtr()
+
+include "config.pxi"
+
+IF HAVE_CUDA:
+  cdef extern from *:
+      CCudaProjector3D* dynamic_cast_cuda_projector "dynamic_cast<astra::CCudaProjector3D*>" (CProjector3D*)
+
+
+def create(config):
+    cdef Config * cfg = utils.dictToConfig(six.b('Projector3D'), config)
+    cdef CProjector3D * proj
+    proj = PyProjector3DFactory.getSingletonPtr().create(cfg[0])
+    if proj == NULL:
+        del cfg
+        raise Exception("Error creating Projector3D.")
+    del cfg
+    return manProj.store(proj)
+
+
+def delete(ids):
+    try:
+        for i in ids:
+            manProj.remove(i)
+    except TypeError:
+        manProj.remove(ids)
+
+
+def clear():
+    manProj.clear()
+
+
+def info():
+    six.print_(wrap_from_bytes(manProj.info()))
+
+cdef CProjector3D * getObject(i) except NULL:
+    cdef CProjector3D * proj = manProj.get(i)
+    if proj == NULL:
+        raise Exception("Projector not initialized.")
+    if not proj.isInitialized():
+        raise Exception("Projector not initialized.")
+    return proj
+
+
+def projection_geometry(i):
+    cdef CProjector3D * proj = getObject(i)
+    return utils.configToDict(proj.getProjectionGeometry().getConfiguration())
+
+
+def volume_geometry(i):
+    cdef CProjector3D * proj = getObject(i)
+    return utils.configToDict(proj.getVolumeGeometry().getConfiguration())
+
+
+def weights_single_ray(i, projection_index, detector_index):
+    raise Exception("Not yet implemented")
+
+
+def weights_projection(i, projection_index):
+    raise Exception("Not yet implemented")
+
+
+def splat(i, row, col):
+    raise Exception("Not yet implemented")
+
+def is_cuda(i):
+    cdef CProjector3D * proj = getObject(i)
+    IF HAVE_CUDA==True:
+      cdef CCudaProjector3D * cudaproj = NULL
+      cudaproj = dynamic_cast_cuda_projector(proj)
+      if cudaproj==NULL:
+          return False
+      else:
+          return True
+    ELSE:
+        return False
diff --git a/python/astra/projector_c.pyx b/python/astra/projector_c.pyx
index f91a8dd..9aa868e 100644
--- a/python/astra/projector_c.pyx
+++ b/python/astra/projector_c.pyx
@@ -47,6 +47,12 @@ from .PyMatrixManager cimport CMatrixManager
 cdef CProjector2DManager * manProj = <CProjector2DManager * >PyProjector2DManager.getSingletonPtr()
 cdef CMatrixManager * manM = <CMatrixManager * >PyMatrixManager.getSingletonPtr()
 
+include "config.pxi"
+
+IF HAVE_CUDA:
+  cdef extern from *:
+      CCudaProjector2D* dynamic_cast_cuda_projector "dynamic_cast<astra::CCudaProjector2D*>" (CProjector2D*)
+
 
 def create(config):
     cdef Config * cfg = utils.dictToConfig(six.b('Projector2D'), config)
@@ -104,6 +110,17 @@ def weights_projection(i, projection_index):
 def splat(i, row, col):
     raise Exception("Not yet implemented")
 
+def is_cuda(i):
+    cdef CProjector2D * proj = getObject(i)
+    IF HAVE_CUDA==True:
+      cdef CCudaProjector2D * cudaproj = NULL
+      cudaproj = dynamic_cast_cuda_projector(proj)
+      if cudaproj==NULL:
+          return False
+      else:
+          return True
+    ELSE:
+        return False
 
 def matrix(i):
     cdef CProjector2D * proj = getObject(i)
diff --git a/python/builder.py b/python/builder.py
index ddca795..cfdb7d1 100644
--- a/python/builder.py
+++ b/python/builder.py
@@ -41,9 +41,22 @@ try:
         usecuda=True
 except KeyError:
     pass
-cfg = open('astra/config.pxi','w')
-cfg.write('DEF HAVE_CUDA=' + str(usecuda) + "\n")
-cfg.close()
+
+cfgToWrite = 'DEF HAVE_CUDA=' + str(usecuda) + "\n"
+cfgHasToBeUpdated = True
+try:
+    cfg = open('astra/config.pxi','r')
+    cfgIn = cfg.read()
+    cfg.close()
+    if cfgIn==cfgToWrite:
+        cfgHasToBeUpdated = False
+except IOError:
+    pass
+
+if cfgHasToBeUpdated:
+    cfg = open('astra/config.pxi','w')
+    cfg.write(cfgToWrite)
+    cfg.close()
 
 cmdclass = { }
 ext_modules = [ ]