246 lines
9.1 KiB
C++
246 lines
9.1 KiB
C++
/*
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Copyright (c) 2015 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Author: Leonardo de Moura
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*/
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#include <algorithm>
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#include <limits>
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#include "kernel/for_each_fn.h"
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#include "kernel/instantiate.h"
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#include "kernel/abstract.h"
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#include "library/trace.h"
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#include "library/fun_info_manager.h"
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namespace lean {
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static name * g_fun_info = nullptr;
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void initialize_fun_info_manager() {
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g_fun_info = new name("fun_info");
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register_trace_class(*g_fun_info);
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}
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void finalize_fun_info_manager() {
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delete g_fun_info;
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}
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#define lean_trace_fun_info(Code) lean_trace(*g_fun_info, Code)
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static bool is_fun_info_trace_enabled() {
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return is_trace_class_enabled(*g_fun_info);
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}
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fun_info_manager::fun_info_manager(type_context & ctx):
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m_ctx(ctx) {
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}
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list<unsigned> fun_info_manager::collect_deps(expr const & type, buffer<expr> const & locals) {
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buffer<unsigned> deps;
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for_each(type, [&](expr const & e, unsigned) {
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if (m_ctx.is_tmp_local(e)) {
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unsigned idx;
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for (idx = 0; idx < locals.size(); idx++)
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if (locals[idx] == e)
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break;
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if (idx < locals.size() && std::find(deps.begin(), deps.end(), idx) == deps.end())
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deps.push_back(idx);
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}
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return has_local(e); // continue the search only if e has locals
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});
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std::sort(deps.begin(), deps.end());
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return to_list(deps);
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}
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/* Store parameter info for fn in \c pinfos and return the dependencies of the resulting type
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(if compute_resulting_deps == true). */
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list<unsigned> fun_info_manager::get_core(expr const & fn, buffer<param_info> & pinfos,
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unsigned max_args, bool compute_resulting_deps) {
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expr type = m_ctx.relaxed_try_to_pi(m_ctx.infer(fn));
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buffer<expr> locals;
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unsigned i = 0;
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while (is_pi(type)) {
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if (i == max_args)
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break;
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expr local = m_ctx.mk_tmp_local_from_binding(type);
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expr local_type = m_ctx.infer(local);
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expr new_type = m_ctx.relaxed_try_to_pi(instantiate(binding_body(type), local));
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bool spec = false;
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bool is_prop = m_ctx.is_prop(local_type);
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bool is_sub = is_prop;
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bool is_dep = !closed(binding_body(type));
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if (!is_sub) {
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// TODO(Leo): check if the following line is a performance bottleneck.
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is_sub = static_cast<bool>(m_ctx.mk_subsingleton_instance(local_type));
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}
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pinfos.emplace_back(spec,
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binding_info(type).is_implicit(),
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binding_info(type).is_inst_implicit(),
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is_prop, is_sub, is_dep, collect_deps(local_type, locals));
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locals.push_back(local);
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type = new_type;
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i++;
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}
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if (compute_resulting_deps)
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return collect_deps(type, locals);
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else
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return list<unsigned>();
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}
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fun_info fun_info_manager::get(expr const & e) {
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auto it = m_cache_get.find(e);
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if (it != m_cache_get.end())
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return it->second;
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buffer<param_info> pinfos;
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auto result_deps = get_core(e, pinfos, std::numeric_limits<unsigned>::max(), true);
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fun_info r(pinfos.size(), to_list(pinfos), result_deps);
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m_cache_get.insert(mk_pair(e, r));
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return r;
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}
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fun_info fun_info_manager::get(expr const & e, unsigned nargs) {
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expr_unsigned key(e, nargs);
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auto it = m_cache_get_nargs.find(key);
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if (it != m_cache_get_nargs.end())
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return it->second;
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buffer<param_info> pinfos;
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auto result_deps = get_core(e, pinfos, nargs, true);
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fun_info r(pinfos.size(), to_list(pinfos), result_deps);
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m_cache_get_nargs.insert(mk_pair(key, r));
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return r;
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}
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/* Return true if there is j s.t. pinfos[j] is not a
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proposition/subsingleton and it dependends of argument i */
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static bool has_nonprop_nonsubsingleton_fwd_dep(unsigned i, buffer<param_info> const & pinfos) {
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for (unsigned j = i+1; j < pinfos.size(); j++) {
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param_info const & fwd_pinfo = pinfos[j];
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if (fwd_pinfo.is_prop() || fwd_pinfo.is_subsingleton())
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continue;
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auto const & fwd_deps = fwd_pinfo.get_dependencies();
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if (std::find(fwd_deps.begin(), fwd_deps.end(), i) != fwd_deps.end()) {
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return true;
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}
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}
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return false;
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}
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void fun_info_manager::trace_if_unsupported(expr const & fn, buffer<expr> const & args, unsigned prefix_sz, fun_info const & result) {
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if (!is_fun_info_trace_enabled())
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return;
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fun_info info = get(fn, args.size());
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buffer<param_info> pinfos;
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to_buffer(info.get_params_info(), pinfos);
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/* Check if all remaining arguments are nondependent or
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dependent (but all forward dependencies are propositions or subsingletons) */
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unsigned i = prefix_sz;
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for (; i < pinfos.size(); i++) {
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param_info const & pinfo = pinfos[i];
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if (!pinfo.is_dep())
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continue; /* nondependent argument */
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if (has_nonprop_nonsubsingleton_fwd_dep(i, pinfos))
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break; /* failed i-th argument has a forward dependent that is not a prop nor a subsingleton */
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}
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if (i == pinfos.size())
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return; // It is *cheap* case
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/* Expensive case */
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/* We generate a trace message IF it would be possible to compute more precise information.
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That is, there is an argument that is a proposition and/or subsingleton, but
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the corresponding pinfo is not a marked a prop/subsingleton.
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*/
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i = 0;
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for (param_info const & pinfo : result.get_params_info()) {
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if (pinfo.is_prop() || pinfo.is_subsingleton())
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continue;
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expr arg_type = m_ctx.infer(args[i]);
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if (m_ctx.is_prop(arg_type) || m_ctx.mk_subsingleton_instance(arg_type)) {
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lean_trace_fun_info(
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tout() << "approximating function information for '" << fn
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<< "', this may affect the effectiveness of the simplifier and congruence closure modules, "
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<< "more precise information can be efficiently computed if all parameters are moved to the beginning of the function\n";);
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return;
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}
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i++;
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}
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}
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unsigned fun_info_manager::get_specialization_prefix_size(expr const & fn, unsigned nargs) {
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/*
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We say a function is "cheap" if it is of the form:
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a) 0 or more dependent parameters p s.t. there is at least one forward dependency x : C[p]
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which is not a proposition nor a subsingleton.
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b) followed by 0 or more nondependent parameter and/or a dependent parameter
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s.t. all forward dependencies are propositions and subsingletons.
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We have a caching mechanism for the "cheap" case.
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The cheap case cover many commonly used functions
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eq : Pi {A : Type} (x y : A), Prop
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add : Pi {A : Type} [s : has_add A] (x y : A), A
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inv : Pi {A : Type} [s : has_inv A] (x : A) (h : invertible x), A
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but it doesn't cover
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p : Pi {A : Type} (x : A) {B : Type} (y : B), Prop
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I don't think this is a big deal since we can write it as:
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p : Pi {A : Type} {B : Type} (x : A) (y : B), Prop
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Therefore, we ignore the non-cheap cases, and pretend they are "cheap".
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If tracing is enabled, we produce a tracing message whenever we find
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a non-cheap case.
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This procecure returns the size of group a)
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*/
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expr_unsigned key(fn, nargs);
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auto it = m_cache_prefix.find(key);
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if (it != m_cache_prefix.end())
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return it->second;
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fun_info info = get(fn, nargs);
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buffer<param_info> pinfos;
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to_buffer(info.get_params_info(), pinfos);
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/* Compute "prefix": 0 or more parameters s.t.
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at lest one forward dependency is not a proposition or a subsingleton */
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unsigned i = 0;
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for (; i < pinfos.size(); i++) {
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param_info const & pinfo = pinfos[i];
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if (!pinfo.is_dep())
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break;
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/* search for forward dependency that is not a proposition nor a subsingleton */
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if (!has_nonprop_nonsubsingleton_fwd_dep(i, pinfos))
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break;
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}
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unsigned prefix_sz = i;
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m_cache_prefix.insert(mk_pair(key, prefix_sz));
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return prefix_sz;
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}
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fun_info fun_info_manager::get_specialized(expr const & a) {
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lean_assert(is_app(a));
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buffer<expr> args;
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expr const & fn = get_app_args(a, args);
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unsigned prefix_sz = get_specialization_prefix_size(fn, args.size());
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unsigned num_rest_args = args.size() - prefix_sz;
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expr g = a;
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for (unsigned i = 0; i < num_rest_args; i++)
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g = app_fn(g);
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expr_unsigned key(g, num_rest_args);
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auto it = m_cache_get_spec.find(key);
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if (it != m_cache_get_spec.end()) {
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return it->second;
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}
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/* fun_info is not cached */
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buffer<param_info> pinfos;
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get_core(fn, pinfos, prefix_sz, false);
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for (unsigned i = 0; i < prefix_sz; i++) {
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pinfos[i].m_specialized = true;
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}
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auto result_deps = get_core(g, pinfos, num_rest_args, true);
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fun_info r(pinfos.size(), to_list(pinfos), result_deps);
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m_cache_get_spec.insert(mk_pair(key, r));
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trace_if_unsupported(fn, args, prefix_sz, r);
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return r;
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}
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}
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