I am creating an object to parse the metadata in HDF5 files in a manner similar to H5_Parse. One difference, though, is that all groups, attributes, datasets, etc. remain open until the object is destroyed. I am parsing many files. If I parse them individually, closing each one before parsing the next, execution time increases linearly with the number of files. If I parse all files at once (closing only after all have been parsed), however, the H5A_* routines taking an increasing amount of time. Is there a reason for this? Below is profiler output for the H5A_* routines for 1) a single file, 2) 10 files parsed together, and 3) 10 files parsed individually. Note the difference between cases for H5A_GET_NUM_ATTRS, H5A_OPEN_NAME, and H5A_OPEN_IDX. The difference compounds for each additional file. Single File ------------------------------------------------------------------------------------------------------- H5A_CLOSE (S) 4452 0.004479 0.000001 0.004479 0.000001 H5A_GET_NAME (S) 3904 0.003998 0.000001 0.003998 0.000001 H5A_GET_NUM_ATTRS (S) 92 0.001094 0.000012 0.001094 0.000012 H5A_GET_SPACE (S) 548 0.001016 0.000002 0.001016 0.000002 H5A_GET_TYPE (S) 548 0.000923 0.000002 0.000923 0.000002 H5A_OPEN_IDX (S) 3904 0.454829 0.000117 0.454829 0.000117 H5A_OPEN_NAME (S) 548 0.066381 0.000121 0.066381 0.000121 10 Files -------------------------------------------------------------------------------------------------------- H5A_CLOSE (S) 44520 0.050385 0.000001 0.050385 0.000001 H5A_GET_NAME (S) 39040 0.040173 0.000001 0.040173 0.000001 H5A_GET_NUM_ATTRS (S) 920 0.033910 0.000037 0.033910 0.000037 H5A_GET_SPACE (S) 5480 0.009080 0.000002 0.009080 0.000002 H5A_GET_TYPE (S) 5480 0.008593 0.000002 0.008593 0.000002 H5A_OPEN_IDX (S) 39040 8.980389 0.000230 8.980389 0.000230 H5A_OPEN_NAME (S) 5480 1.308467 0.000239 1.308467 0.000239 10 Files Individually ---------------------------------------------------------------------------------------------------------- H5A_CLOSE (S) 44520 0.044785 0.000001 0.044785 0.000001 H5A_GET_NAME (S) 39040 0.039924 0.000001 0.039924 0.000001 H5A_GET_NUM_ATTRS (S) 920 0.027584 0.000030 0.027584 0.000030 H5A_GET_SPACE (S) 5480 0.008716 0.000002 0.008716 0.000002 H5A_GET_TYPE (S) 5480 0.008387 0.000002 0.008387 0.000002 H5A_OPEN_IDX (S) 39040 4.474848 0.000115 4.474848 0.000115 H5A_OPEN_NAME (S) 5480 0.665722 0.000121 0.665722 0.000121