Package noaa.coastwatch.util.chunk

Class ExpressionFunction

java.lang.Object
noaa.coastwatch.util.chunk.ExpressionFunction
All Implemented Interfaces:
ChunkFunction
public class ExpressionFunction extends Object implements ChunkFunction
The ExpressionFunction class implements the ChunkFunction interface to perform mathematical expression calculations on chunk data.
Since:
3.4.0
Author:
Peter Hollemans

  • Constructor Details

    • ExpressionFunction

      public ExpressionFunction()

  • Method Details

    • setSkipMissing

      public void setSkipMissing(boolean flag)
      Sets the skip missing flag (by default set to false).
      Parameters:
      flag - the new flag value. When the skip missing flag is set to true, the expression is not evaluated at all if any of the input values are set to missing. This has the advantage of saving computation time. When the flag is set to false, the expression is always evaluated and any missing values are used in the computation. This is important in cases when the expression includes a test for missing values such as an isNaN test, or if the data contains missing values that should actually be used in a computation (in some cases, flag variables are assigned a missing value of zero when they shouldn't be). Essentially the skip missing flag acts as an optimization in certain cases.

    • init

      public void init(ExpressionParser parser, DataChunk resultPrototype)
      Initializes this function with the specified parser that will be used to evaluate expression values. The parser should be initialized and the expression parsed before calling this method.
      Parameters:
      parser - the initialized and parsed expression parser.
      resultPrototype - the result chunk prototype. The prototype will be used to generate new results when the apply(noaa.coastwatch.util.chunk.ChunkPosition, java.util.List<noaa.coastwatch.util.chunk.DataChunk>) method is called.

    • getMemory

      public long getMemory(ChunkPosition pos, int chunks)
      Description copied from interface: ChunkFunction
      Estimates the memory requirements for processing a chunk of data at the specified position, not including the input and output chunk internal data arrays.
      Specified by:
      getMemory in interface ChunkFunction
      Parameters:
      pos - the position to estimate the memory usage.
      chunks - the number of input chunks that will be processed at once.
      Returns:
      the memory in bytes.

    • apply

      public DataChunk apply(ChunkPosition pos, List<DataChunk> inputChunks)
      Description copied from interface: ChunkFunction
      Applies some function to a list of chunks.
      Specified by:
      apply in interface ChunkFunction
      Parameters:
      pos - the position to perform the function.
      inputChunks - the list of chunks as input to the function.
      Returns:
      the output chunk of the function, or null if no valid output chunk could be computed.