Module oc_cgstep_mod

1.

Purpose: conjugate-gradient descent step

		      CGSTEP($\bold m,\bold R,\bold g,\bold G$)  {
		 		  $\Delta = \left (\G^*\cdot\G\right ) \left (\S^*\cdot\S\right ) - \left (\S^*\cdot\G\right ) \left (\G^*\cdot\S\right )$
		 		  $\alpha= -\frac{1}{\Delta}\left [+\left (\S^*\cdot\S\right ) \left (\G^*\cdot\R\right ) -\left (\G^*\cdot\S\right ) \left (\S^*\cdot\R\right ) \right ]$
		 		  $\b = -\frac{1}{\Delta}\left [-\left (\G^*\cdot\S\right ) \left (\G^*\cdot\R\right ) +\left (\G^*\cdot\G\right ) \left (\S^*\cdot\R\right ) \right ]$
		 		 		$\left \{\begin{array}
{l} \bold m=\bold m+\alpha\bold g+\b\bold s\\  \bold R=\bold R+\alpha\bold G+\b\S \end{array}\right .$ 
		 		 }

2.

Functions and subroutines

(a)

integer function oc_cgstep(forget,x_,g_,rr_,gg_,s_,ss_,maxmem)

• forget: re-initialize operator
• x_: model file tag
• >_: gradient file tag
• rr_: residual file tag
• >g_: conjugate gradient file tag
• s_: previous step file tag
• ss_: conjugate previous step file tag