# -*- coding: utf-8 -*-
"""
Created on Fri May 17 16:20:21 2019

@author: 
"""

import math

"""
*> \brief \b DSCAL
*
*  =========== DOCUMENTATION ===========
*
* Online html documentation available at
*            http://www.netlib.org/lapack/explore-html/
*
*  Definition:
*  ===========
*
*       SUBROUTINE DSCAL(N,DA,DX,INCX)
*
*       .. Scalar Arguments ..
*       DOUBLE PRECISION DA
*       INTEGER INCX,N
*       ..
*       .. Array Arguments ..
*       DOUBLE PRECISION DX(*)
*       ..
*
*
*> \par Purpose:
*  =============
*>
*> \verbatim
*>
*>    DSCAL scales a vector by a constant.
*>    uses unrolled loops for increment equal to 1.
*> \endverbatim
*
*  Arguments:
*  ==========
*
*> \param[in] N
*> \verbatim
*>          N is INTEGER
*>         number of elements in input vector(s)
*> \endverbatim
*>
*> \param[in] DA
*> \verbatim
*>          DA is DOUBLE PRECISION
*>           On entry, DA specifies the scalar alpha.
*> \endverbatim
*>
*> \param[in,out] DX
*> \verbatim
*>          DX is DOUBLE PRECISION array, dimension ( 1 + ( N - 1)*abs( INCX ) )
*> \endverbatim
*>
*> \param[in] INCX
*> \verbatim
*>          INCX is INTEGER
*>         storage spacing between elements of DX
*> \endverbatim
*
*  Authors:
*  ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \date November 2017
*
*> \ingroup double_blas_level1
*
*> \par Further Details:
*  =====================
*>
*> \verbatim
*>
*>     jack dongarra, linpack, 3/11/78.
*>     modified 3/93 to return if incx .le. 0.
*>     modified 12/3/93, array(1) declarations changed to array(*)
*> \endverbatim
*>
*  =====================================================================
"""
#SUBROUTINE dscal(N,DA,DX,INCX)
def dscal(n, da, dx, incx):

    #*
    #*  -- Reference BLAS level1 routine (version 3.8.0) --
    #*  -- Reference BLAS is a software package provided by Univ. of
    #*  Tennessee,    --
    #*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG
    #*  Ltd..--
    #*     November 2017
    #*
    #*     .. Scalar Arguments ..
    #DOUBLE PRECISION DA
    #INTEGER INCX,N
    #*     ..
    #*     .. Array Arguments ..
    #DOUBLE PRECISION DX(*)
    
    dxSize = 1 + (n-1)*abs(incx)
    #dxOut = [0.0e0 for i in range(dxSize)]
    #*     ..
    #*
    #*  =====================================================================
    #*
    #*     .. Local Scalars ..
    #INTEGER I,M,MP1,NINCX
    i = 0
    m = 0
    mp1 = 0
    nincx = 0
    
    #print("DSCAL: n ", n, " incx ", incx, " da ", da)
    #print("dx in ", [dx[kk] for kk in range(n)])
    
    #*     ..
    #*     .. Intrinsic Functions ..
    #INTRINSIC mod
    #*     ..
    #IF (n.LE.0 .OR. incx.LE.0) RETURN
    if ( (n > 0) and (incx > 0) ):
        
        #IF (incx.EQ.1) THEN
        if (incx == 1):
            #*
            #*        code for increment equal to 1
            #*
            #*
            #*        clean-up loop
            #*
            
            m = n % 5
            #IF (m.NE.0) THEN
            if (m != 0):
                
                #DO i = 1,m
                for i in range(m):
                    dx[i] = da*dx[i]
                    #print("DSCAL 1: i ", i, " dx ", dx[i])
            
                #IF (n.LT.5) RETURN
            #END IF
            #if ( (m == 0) and (n >= 5) ):
            if ( n >= 5 ):    

                mp1 = m + 1

                #DO i = mp1,n,5
#               print("DSCAL: n ", n, " m ", m, " mp1 ", mp1, " da ", da)
                for i in range(mp1-1, n, 5):
#                    print("DSCAL 2: i ", i, " dx(i... i+4) ",\
#                          dx[i], dx[i+1], dx[i+2], dx[i+3], dx[i+4])
                    dx[i] = da*dx[i]
                    dx[i+1] = da*dx[i+1]
                    dx[i+2] = da*dx[i+2]
                    dx[i+3] = da*dx[i+3]
                    dx[i+4] = da*dx[i+4]
                    #print("DSCAL 2: i ", i, " dx(i... i+4) ",\
                    #      dx[i], dx[i+1], dx[i+2], dx[i+3], dx[i+4])
         
        else:
            #*
            #*        code for increment not equal to 1
            #*
            nincx = n*incx
            #DO i = 1,nincx,incx
            for i in range(0, nincx, incx):
                dx[i] = da*dx[i]
                #print("DSCAL 3: i ", i, " dx ", dx[i])
         
      
      
    return dx