Fortran 2003 VECTOR types.

This package contains a Fortran 2003 dynamic memory module. The VECTOR type is a dynamically resizing two-dimensional array with both REAL and INTEGER options (REALVECTOR and INTVECTOR types). The first dimension of a VECTOR object VEC is fixed upon initialization. The second dimension self-resizes based on the following rules:

• If VEC%LENGTH == 0, then no memory is allocated.
• If VEC%LENGTH overflows VEC%MAXLEN, then double the size of VEC%MAXLEN (unless VEC%MAXLEN == 0, then initialize to VEC%MAXLEN = 8).
• If VEC%LENGTH underflows VEC%MAXLEN, occupying less than half the total storage, reclaim half the size allocated to VEC.

Contents

• Vector.f90 contains the VECTOR_MOD module containing the complete VECTOR class (interfaces, functions, subroutines, and data types).
• main.f90 contains driver code in the form of a command line testing interface.
• Makefile is a simple makefile for this project.

Usage

To use the REALVECTOR and INTVECTOR data types, include the following module: USE VECTOR_CLASS The two types provided are TYPE(REALVECTOR) and TYPE(INTVECTOR). The REALVECTOR type uses the R8 data type for 64-bit real arithmetic, provided in the same module. All internal memory for both VECTOR types is private, and the VECTOR must be interfaced using the provided functions and subroutines.

All subroutines related to the Vector class use an error flag ISTAT to report successful operations. The scheme is as follows:

• IERR = 0 : SUCCESS
• IERR < 0 : ILLEGAL INPUT AT ARG : (-IERR)
• IERR > 0 : MEMORY ALLOCATION/DEALLOCATION ERROR

User Interface

The following 2 subroutines are used to safely allocate and deallocate VECTOR objects:

• VEC = [REAL|INT]VECTOR([DIM, ISTAT]) allocates VEC as a new VECTOR object. The optional argument DIM, if provided, specifies the length of the first (static) dimension. If omitted, the first dimension is assumed to have length 1 (note, that even if it has length 1, the first dimension must still be treated as a vector, not a scalar).
• VEC%FREE([ISTAT]) frees any memory currently allocated for VEC.

The following 5 subroutines are used to manage memory. Note, that the argument ITEM must match the first dimension and type of VEC.

• VEC%PUSH(ITEM[, ISTAT]) pushes ITEM(:) to the end of VEC, resizing if necessarry.
• VEC%POP(ITEM[, ISTAT]) pops the top item off the back of VEC, resizing if necessarry and returns the value in ITEM(:).
• VEC%INSERT(ITEM, IND[, ISTAT]) inserts ITEM at location IND.
• VEC%DELETE(IND[, ISTAT]) deletes the item at location IND.
• VEC%SET(IND, ITEM[, ISTAT]) sets the value of VEC location IND to ITEM(:).

The following 4 functions are provided for data access:

• VEC%ITEM(IND[, IERR]) returns the one-dimensional array located at index IND.
• VEC%DAT() returns the entire two-dimensional data set currently stored in VEC (first dimension fixed, second dynamic).
• VEC%DIM() returns the integer valued size of the first (static) dimension of VEC.
• VEC%LENGTH() returns the integer valued size of the second (dynamic) dimension of VEC.

Installation

To install, simply pull this repo then use the Makefile to build the contents in your local directory. make -B

Test cases

After installing, try running the provided command line interface to test the VECTOR class. ./main For more usage examples, consider referencing the code in main.f90.

Author

• Tyler H. Chang - Primary author

Footnotes

This code does not represent the most efficient means for dynamic memory allocation in Fortran 2003 for most real-world problems. However, it is a general solution that will work for a wide range of use cases.