Calculating file sizes

Windows OS

AcqKnowledge 64-bit and Biopac Student Lab 32-bit

There are multiple cases (configs) related to the issue of Memory/HardDrive/32bit-64bit limitations

• All released versions have the same single limit applied to channel(s) length in SAMPLES.
  Channel length is limited by 2 Giga Samples = 2,147,483,648 samples
  • Any EDIT functions (copy/paste, resampling, merging, duplicate channel, remove waveform, cut selected data area) cannot jump over this 2 GigaSamples limit

AcqKnowledge  64-bit offers big improvements in terms of file size and memory limitation

File functions

• AcqKnowledge 64-bit can read/save data files of virtually unlimited size in bytes.
  • The only limitation is free hard disk space.
  • AcqKnowledge 64-bit cannot avoid 2 GigaSamples limit per channel, but can handle 100+ calculation/transformation channels (8 bytes per sample).
    • Example: AcqKnowledge 64-bit was tested with data files of about 45 Gbytes – 4 analog channels + 4 calc channels, length is about 1.1 GigaSamples

Memory functions

• AcqKnowledge 64-bit utilizes two features—64-bit addressing and Virtual memory supported by Windows—and allow to handle data file which size is limited by Physical RAM and Virtual Memory settings of Windows OS.
• AcqKnowledge 64-bit can allocate ALL physical RAM of the computer to load data into the memory for transformations, and also can utilize virtual memory of the computer.
• Using of virtual memory for transformations or “load all data into memory” is very helpful—it does not limit user to transform extremely long data channels with annoying prompt “Not enough memory to execute transformation.” However, user should expect delays with transformations because virtual memory means using hard drive as memory substitute.
• MS Windows settings that control the size of virtual memory are explained here: https://www.geeksinphoenix.com/blog/post/2016/05/10/how-to-manage-windows-10-virtual-memory.aspx
  • Example: Computer has 16GB of RAM and virtual memory configuration for PAGE FILE is set to Initial size = 24GB and Max size = 48GB. Under this setting, AcqKnowledge can load into the memory data file of about 16G + 48GB = 64 GB (minus memory allocated by OS Windows and other processes)

BSL 4.1.2 or above

File and memory functions are unchanged at 2 GigaSamples of length and 4 GBytes of file size. BSL 4.1.2 or above can allocate max 2 GBytes of RAM for transformations.

• This build is known to crash when handling very big files, especially if duplicating channels

MacOS

• AcqKnowledge 3.9.0 and above files (including merged files) are not limited
• AcqKnowledge 3.8.2 and below files (including merged files) cannot exceed 2 GB
• BSL Lessons and BSL PRO files cannot exceed 2 GB

 Memory required (bytes) = [(8C + 2A) x S x T] + 1 MB*

C = Number of calculation channels

A = Number of analog channels

S = Sample rate (samples/second)

T = Recording time (acquisition length; when sample rate is samples per second, T is in SECONDS)

* 1 MB = MINIMUM memory overhead required to store file information

• Journals, events, and other information are variable and will also require more disk space.
• Once analog channels are filtered or otherwise transformed, the required amount of storage will increase to 8 bytes per sample, identical to calculation channels.
• It is not possible to perform any transformations for acquisitions where converting analog channels to floating point will exceed 2 GB.
• Memory overhead requirement may increase significantly with
  • many events with long labels
  • long and rich-formatted journal
  • opened DataViews
  • MetaChannels – overhead includes Hardware Settings and MetaChannels support (max 16 metachannels per each of 16 calc channels –> 256 “calc” channels)
  • Smart Amplifier information as part of Hardware Settings section of graphfile take storage

Note that all 16 digital channels allocate 2 bytes (16 bit – 1 bit per digital channel). So, having at least 1 digital channel ON will cause allocation of 2 bytes  per sample.

Refer to the software guide available under the program Help menu for setup and analysis guidelines when working with large files.