/*
**
** DGESL benchmark
**
** We would like to declare a[][lda], but c does not allow it. In this
** function, references to a[i][j] are written a[lda*i+j].
**
** dgesl solves the double precision system
** a * x = b or trans(a) * x = b
** using the factors computed by dgeco or dgefa.
**
** on entry
**
** a double precision[n][lda]
** the output from dgeco or dgefa.
**
** lda integer
** the leading dimension of the array a .
**
** n integer
** the order of the matrix a .
**
** ipvt integer[n]
** the pivot vector from dgeco or dgefa.
**
** b double precision[n]
** the right hand side vector.
**
** job integer
** = 0 to solve a*x = b ,
** = nonzero to solve trans(a)*x = b where
** trans(a) is the transpose.
**
** on return
**
** b the solution vector x .
**
** error condition
**
** a division by zero will occur if the input factor contains a
** zero on the diagonal. technically this indicates singularity
** but it is often caused by improper arguments or improper
** setting of lda . it will not occur if the subroutines are
** called correctly and if dgeco has set rcond .gt. 0.0
** or dgefa has set info .eq. 0 .
**
** to compute inverse(a) * c where c is a matrix
** with p columns
** dgeco(a,lda,n,ipvt,rcond,z)
** if (!rcond is too small){
** for (j=0,j<p,j++)
** dgesl(a,lda,n,ipvt,c[j][0],0);
** }
**
** linpack. this version dated 08/14/78 .
** cleve moler, university of new mexico, argonne national lab.
**
** functions
**
** blas daxpy,ddot
*/
static void dgesl(REAL *a,int lda,int n,int *ipvt,REAL *b,int job,int roll)
{
REAL t;
int k,kb,l,nm1;
if (roll)
{
nm1 = n - 1;
if (job == 0)
{
/* job = 0 , solve a * x = b */
/* first solve l*y = b */
if (nm1 >= 1)
for (k = 0; k < nm1; k++)
{
l = ipvt[k];
t = b[l];
if (l != k)
{
b[l] = b[k];
b[k] = t;
}
daxpy_r(n-(k+1),t,&a[lda*k+k+1],1,&b[k+1],1);
}
/* now solve u*x = y */
for (kb = 0; kb < n; kb++)
{
k = n - (kb + 1);
b[k] = b[k]/a[lda*k+k];
t = -b[k];
daxpy_r(k,t,&a[lda*k+0],1,&b[0],1);
}
}
else
{
/* job = nonzero, solve trans(a) * x = b */
/* first solve trans(u)*y = b */
for (k = 0; k < n; k++)
{
t = ddot_r(k,&a[lda*k+0],1,&b[0],1);
b[k] = (b[k] - t)/a[lda*k+k];
}
/* now solve trans(l)*x = y */
if (nm1 >= 1)
for (kb = 1; kb < nm1; kb++)
{
k = n - (kb+1);
b[k] = b[k] + ddot_r(n-(k+1),&a[lda*k+k+1],1,&b[k+1],1);
l = ipvt[k];
if (l != k)
{
t = b[l];
b[l] = b[k];
b[k] = t;
}
}
}
}
else
{
nm1 = n - 1;
if (job == 0)
{
/* job = 0 , solve a * x = b */
/* first solve l*y = b */
if (nm1 >= 1)
for (k = 0; k < nm1; k++)
{
l = ipvt[k];
t = b[l];
if (l != k)
{
b[l] = b[k];
b[k] = t;
}
daxpy_ur(n-(k+1),t,&a[lda*k+k+1],1,&b[k+1],1);
}
/* now solve u*x = y */
for (kb = 0; kb < n; kb++)
{
k = n - (kb + 1);
b[k] = b[k]/a[lda*k+k];
t = -b[k];
daxpy_ur(k,t,&a[lda*k+0],1,&b[0],1);
}
}
else
{
/* job = nonzero, solve trans(a) * x = b */
/* first solve trans(u)*y = b */
for (k = 0; k < n; k++)
{
t = ddot_ur(k,&a[lda*k+0],1,&b[0],1);
b[k] = (b[k] - t)/a[lda*k+k];
}
/* now solve trans(l)*x = y */
if (nm1 >= 1)
for (kb = 1; kb < nm1; kb++)
{
k = n - (kb+1);
b[k] = b[k] + ddot_ur(n-(k+1),&a[lda*k+k+1],1,&b[k+1],1);
l = ipvt[k];
if (l != k)
{
t = b[l];
b[l] = b[k];
b[k] = t;
}
}
}
}
}
void dgesl(int *a,int lda,int n,int *ipvt,int *b,int job,int roll)
{
int t;
int k,kb,l,nm1;
if (roll>=1)
{
nm1 = n - 1;
if (job == 0)
{
if (nm1 >= 1)
for (k = 0; k < nm1; k++)
{
l = ipvt[k];
t = b[l];
if (!(l == k))
{
b[l] = b[k];
b[k] = t;
}
daxpy_r(n-(k+1),t,&a[lda*k+k+1],1,&b[k+1],1);
}
for (kb = 0; kb < n; kb++)
{
k = n - (kb + 1);
b[k] = b[k]/a[lda*k+k];
t = -b[k];
daxpy_r(k,t,&a[lda*k+0],1,&b[0],1);
}
}
else
{
for (k = 0; k < n; k++)
{
t = ddot_r(k,&a[lda*k+0],1,&b[0],1);
b[k] = (b[k] - t)/a[lda*k+k];
}
if (nm1 >= 1)
for (kb = 1; kb < nm1; kb++)
{
k = n - (kb+1);
b[k] = b[k] + ddot_r(n-(k+1),&a[lda*k+k+1],1,&b[k+1],1);
l = ipvt[k];
if (!(l == k))
{
t = b[l];
b[l] = b[k];
b[k] = t;
}
}
}
}
else
{
nm1 = n - 1;
if (job == 0)
{
if (nm1 >= 1)
for (k = 0; k < nm1; k++)
{
l = ipvt[k];
t = b[l];
if (!(l == k))
{
b[l] = b[k];
b[k] = t;
}
daxpy_ur(n-(k+1),t,&a[lda*k+k+1],1,&b[k+1],1);
}
for (kb = 0; kb < n; kb++)
{
k = n - (kb + 1);
b[k] = b[k]/a[lda*k+k];
t = -b[k];
daxpy_ur(k,t,&a[lda*k+0],1,&b[0],1);
}
}
else
{
for (k = 0; k < n; k++)
{
t = ddot_ur(k,&a[lda*k+0],1,&b[0],1);
b[k] = (b[k] - t)/a[lda*k+k];
}
if (nm1 >= 1)
for (kb = 1; kb < nm1; kb++)
{
k = n - (kb+1);
b[k] = b[k] + ddot_ur(n-(k+1),&a[lda*k+k+1],1,&b[k+1],1);
l = ipvt[k];
if (!(l == k))
{
t = b[l];
b[l] = b[k];
b[k] = t;
}
}
}
}
}
