Example 1

The program in Fig. 3.1 illustrates the use of an LAPACK95 driver routine, LA_GESV. This routine solves a linear system of equations $AX = B$, where $A$ is a square matrix and B is a vector or matrix containing the right-hand side vector(s). (See Section 5.1.1). In this application B is a matrix.
Remarks:

• Statement 2 includes the la_precision.mod module from LAPACK95 and sets the precision to single precision (SP) via the internal parameter WP (working precision). If SP is replaced by DP then the precision is set to double precision.
  
• Statement 3 includes the interface block of the driver routine LA_GESV from the f95_lapack.mod module of LAPACK95. All driver routine interfaces are contained in this module.
  
• Statement 7 defines arguments A and B to be allocatable real single-precision arrays. The program works in complex arithmetic if REAL(WP) is replaced by COMPLEX(WP).
  
• Statements 9-11 allocate A and B and assign data to these arrays.
  
• Statement 12 calls LA_GESV to solve the system. On exit, the solution matrix X is stored in array B.
  
• Statement 15 prints X.

Figure 3.1: Example program calling an LAPACK95 driver routine.