[Chimera-users] Representation of volume data in memory
goddard at cgl.ucsf.edu
Tue Jan 30 16:05:43 PST 2007
I suspect 2-byte integers are not faster to access or compute with then
4-byte floats on modern CPUs. But more of the map will fit into the
CPUs cache which could improve bandwidth and could make computing a
contour surface faster. But I don't think that will be significant.
You would need to test it to know. Chimera keeps the native data type
of the map to conserve memory when reading large maps.
> does this mean that a 2-byte integer format of a file will display
> faster / render triangles faster than the equivalent sized 4-byte float
> Thomas Goddard wrote:
>> Hi Jeff,
>> Chimera keeps volume data in memory using the same numeric value
>> types that are present in the file, for example, 32-bit float, 16-bit
>> integer, 8-bit integer.
>> Volume data is copied only when necessary -- for instance, using the
>> Gaussian Filter tool creates a floating point copy of the data since
>> Gaussian convolution of integer data produces a floating point result.
>> Jeff wrote:
>>> does chimera store all values as float internally (even if the
>>> original map is in 2 byte integers), making the mode of the MRC file
>>> irrelevant to chimera's performance?
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