blis/frame/3/her2k/bli_her2k_front.c

/*

   BLIS
   An object-based framework for developing high-performance BLAS-like
   libraries.

   Copyright (C) 2014, The University of Texas at Austin

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   modification, are permitted provided that the following conditions are
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      notice, this list of conditions and the following disclaimer.
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      notice, this list of conditions and the following disclaimer in the
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      contributors may be used to endorse or promote products derived
      from this software without specific prior written permission.

   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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   HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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*/

#include "blis.h"

void bli_her2k_front
     (
       obj_t*  alpha,
       obj_t*  a,
       obj_t*  b,
       obj_t*  beta,
       obj_t*  c,
       cntx_t* cntx,
       rntm_t* rntm,
       cntl_t* cntl
     )
{
	bli_init_once();

	obj_t    alpha_conj;
	obj_t    c_local;
	obj_t    a_local;
	obj_t    bh_local;
	obj_t    b_local;
	obj_t    ah_local;

	// Check parameters.
	if ( bli_error_checking_is_enabled() )
		bli_her2k_check( alpha, a, b, beta, c, cntx );

	// If alpha is zero, scale by beta, zero the imaginary components of
	// the diagonal elements, and return.
	if ( bli_obj_equals( alpha, &BLIS_ZERO ) )
	{
		bli_scalm( beta, c );
		bli_setid( &BLIS_ZERO, c );
		return;
	}

	// Alias A, B, and C in case we need to apply transformations.
	bli_obj_alias_to( a, &a_local );
	bli_obj_alias_to( b, &b_local );
	bli_obj_alias_to( c, &c_local );
	bli_obj_set_as_root( &c_local );

	// For her2k, the first and second right-hand "B" operands are simply B'
	// and A'.
	bli_obj_alias_to( b, &bh_local );
	bli_obj_induce_trans( &bh_local );
	bli_obj_toggle_conj( &bh_local );
	bli_obj_alias_to( a, &ah_local );
	bli_obj_induce_trans( &ah_local );
	bli_obj_toggle_conj( &ah_local );

	// Initialize a conjugated copy of alpha.
	bli_obj_scalar_init_detached_copy_of( bli_obj_dt( a ),
	                                      BLIS_CONJUGATE,
	                                      alpha,
	                                      &alpha_conj );

	// An optimization: If C is stored by rows and the micro-kernel prefers
	// contiguous columns, or if C is stored by columns and the micro-kernel
	// prefers contiguous rows, transpose the entire operation to allow the
	// micro-kernel to access elements of C in its preferred manner.
	if ( bli_cntx_l3_vir_ukr_dislikes_storage_of( &c_local, BLIS_GEMM_UKR, cntx ) )
	{
		bli_obj_swap( &a_local, &bh_local );
		bli_obj_swap( &b_local, &ah_local );

		bli_obj_induce_trans( &a_local );
		bli_obj_induce_trans( &bh_local );
		bli_obj_induce_trans( &b_local );
		bli_obj_induce_trans( &ah_local );

		bli_obj_induce_trans( &c_local );
	}

	// Parse and interpret the contents of the rntm_t object to properly
	// set the ways of parallelism for each loop, and then make any
	// additional modifications necessary for the current operation.
	bli_rntm_set_ways_for_op
	(
	  BLIS_HER2K,
	  BLIS_LEFT, // ignored for her[2]k/syr[2]k
	  bli_obj_length( &c_local ),
	  bli_obj_width( &c_local ),
	  bli_obj_width( &a_local ),
	  rntm
	);

	// A sort of hack for communicating the desired pach schemas for A and B
	// to bli_gemm_cntl_create() (via bli_l3_thread_decorator() and
	// bli_l3_cntl_create_if()). This allows us to access the schemas from
	// the control tree, which hopefully reduces some confusion, particularly
	// in bli_packm_init().
	if ( bli_cntx_method( cntx ) == BLIS_NAT )
	{
		bli_obj_set_pack_schema( BLIS_PACKED_ROW_PANELS, &a_local );
		bli_obj_set_pack_schema( BLIS_PACKED_COL_PANELS, &bh_local );
		bli_obj_set_pack_schema( BLIS_PACKED_ROW_PANELS, &b_local );
		bli_obj_set_pack_schema( BLIS_PACKED_COL_PANELS, &ah_local );
	}
	else // if ( bli_cntx_method( cntx ) != BLIS_NAT )
	{
		pack_t schema_a = bli_cntx_schema_a_block( cntx );
		pack_t schema_b = bli_cntx_schema_b_panel( cntx );

		bli_obj_set_pack_schema( schema_a, &a_local );
		bli_obj_set_pack_schema( schema_b, &bh_local );
		bli_obj_set_pack_schema( schema_a, &b_local );
		bli_obj_set_pack_schema( schema_b, &ah_local );
	}

	// Invoke herk twice, using beta only the first time.

	// Invoke the internal back-end.
	bli_l3_thread_decorator
	(
	  bli_gemm_int,
	  BLIS_HERK, // operation family id
	  alpha,
	  &a_local,
	  &bh_local,
	  beta,
	  &c_local,
	  cntx,
	  rntm,
	  cntl
	);

	bli_l3_thread_decorator
	(
	  bli_gemm_int,
	  BLIS_HERK, // operation family id
	  &alpha_conj,
	  &b_local,
	  &ah_local,
	  &BLIS_ONE,
	  &c_local,
	  cntx,
	  rntm,
	  cntl
	);

	// The Hermitian rank-2k product was computed as A*B'+B*A', even for
	// the diagonal elements. Mathematically, the imaginary components of
	// diagonal elements of a Hermitian rank-2k product should always be
	// zero. However, in practice, they sometimes accumulate meaningless
	// non-zero values. To prevent this, we explicitly set those values
	// to zero before returning.
	bli_setid( &BLIS_ZERO, &c_local );
}