All smiles, except on subsidies. PROPELLED BY PROSPERITY

It will be remembered as the pageant of prosperity. The seven leaders of major industrial powers wrapped up what might go down as their most discord-free summit ever.

The leaders of Japan, Britain, France, Italy, West Germany, the United States, and the host, Canada, failed to tackle some key issues. But Canadian Prime Minister Brian Mulroney harnessed enough ``political willpower'' to get an agreement to help the most impoverished people of the world through a debt-relief program. And, in a high-level swat at drug barons, they agreed that, as the illicit drug trade becomes more complex, they should find additional ways to ``trace, freeze, and confiscate'' the booty of drug pushers and money launderers.

The summit leaders will leave Canada's financial hub with many topics to discuss at next year's summit, which they have agreed to hold in Paris on Bastille Day (July 14).

Likely to be on the agenda for the new US president will be the more troublesome topics of this summit: ending agricultural subsidies, breaking down structural barriers to commerce, and dealing with such hot political issues as the Middle East and South Africa.

It's also possible that President Reagan helped set part of the agenda for next year's summit. His aides say Mr. Reagan used the intimacy of his final summit dinner to focus on what he considers to be the emerging issue of management of technology in a global context.

For example, during last October 19th's stock market plunge, computer-generated trading threw investors off balance on a worldwide basis. ``You have to make the right policy decisions,'' a White House aide said. ``Without the G7 [the `Group of Seven' summit nations] working together, you could make the wrong moves.''

Reagan indicated to the other world leaders that the solution to dealing with technology in a rapidly changing world is flexibility. It is for that reason, Reagan said, that he opposed the plant-closing provision in the trade bill he vetoed last month.

``People must be ready to adjust,'' says the White House aide, ``and a seemingly harmless thing like a plant closing, when multiplied by 2,000 labor situations, does not give you flexibility.''

As a gesture to Reagan, the summiteers put together a communiqu'e that used many of the President's free-market and low-tax concepts in the preamble and much of the conclusion. As expected, it had a self-congratulatory air. US officials believe this is justified since the economies of the seven countries are all in good shape.

For the President, his aides say, the Toronto summit was a bittersweet moment, since he has developed a close relationship with some of the world leaders. Friendships aside, the stickiest issue of the day turned out to be agricultural subsidies.

The US and Canada were pressing for strong language from the summiteers, indicating they wanted negotiators to work quickly to end farm subsidies.

Reagan, in fact, has made an ideological drive for an end to farm subsidies by the year 2000. The Europeans want less specific language, without a set date for a phasing-out of such subsidies.

The semantics are politically important. West German Chancellor Helmut Kohl, French President Fran,cois Mitterrand, and Japanese Prime Minister Noboru Takeshita all depend on farm votes for their political base.

At the same time, the Reagan administration is taking a political gamble. The farm vote is important to the Republicans in the November presidential elections. And US farmers, after suffering through a difficult series of years, are being buffeted by a severe drought.

The summiteers fared better on other issues. They agreed to aid the ``poorest-of-the-poor'' nations with a debt-relief plan that will permit the seven nations to choose from a ``menu of options.''

This marks a breakthrough because the group, as part of the Paris Club, the main lenders to third-world countries, have agreed to maintain the same policies toward debtors.

The agreement reached here allows them to take different routes toward granting relief. Thus, the US can choose to extend the maturity of the official debt, without actually forgiving it. And the European countries, which have much stronger trade ties with impoverished African nations, can actually forgive the debt.

As is the custom with such summits, the world leaders discussed political issues over meals. It was at these repasts that Reagan told the summiteers about his ``other summit'' in Moscow with Soviet leader Mikhail Gorbachev.

The summits also provided a showcase for Mr. Mulroney, who got the group to endorse the Free Trade Agreement between Canada and the US.

In the meetings, the Japanese made it clear they did not want this agreement, and the integration of the European Community in 1992, to result in exclusionary policies.

WHAT THEY ACHIEVED

US changed attitude on debt to poorest nations and accepted idea of more lender flexibility.

Agreed to confiscate proceeds of international drug traffickers and to curb money laundering.

Endorsed principle that hijacked planes should not be allowed to take off once they have landed.

Agreed to use system of commodity indicators to track each other's economies.

What the summit did not do

Raise issue of United States budget deficit.

Tackle problem of trade imbalances.

Make substantial progress on cutting back agricultural subsidies.

Adopt any new approaches to problem of Latin American debt burden.

Set any timetables for removal of structural barriers to international trade and commerce.

Agree on concerted action for ending apartheid policies in South Africa.

Launch new efforts to end Middle East hostilities.